{"id":1267,"date":"2019-07-26T19:13:46","date_gmt":"2019-07-26T23:13:46","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/chapter\/unit-3-biochemistry\/"},"modified":"2024-04-25T01:07:48","modified_gmt":"2024-04-25T05:07:48","slug":"unit-3-biochemistry","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/chapter\/unit-3-biochemistry\/","title":{"raw":"Unit 3: Biochemistry","rendered":"Unit 3: Biochemistry"},"content":{"raw":"<div class=\"unit-3:-biochemistry\">\r\n<div class=\"textbox shaded\">\r\n\r\n<strong>Unit outline<\/strong>\r\n\r\n<a href=\"#3.1\"><strong>Part 1.<\/strong> Chemistry of carbon<\/a>\r\n\r\n<a href=\"#3.2\"><strong>Part 2.<\/strong> Carbohydrates<\/a>\r\n<ul>\r\n \t<li><a href=\"#3.2a\">Monosaccharides<\/a><\/li>\r\n \t<li><a href=\"#3.2b\">Disaccharides<\/a><\/li>\r\n \t<li><a href=\"#3.2c\">Polysaccharides<\/a><\/li>\r\n \t<li><a href=\"#3.2d\">Functions of carbohydrates<\/a><\/li>\r\n<\/ul>\r\n<a href=\"#3.3\"><strong>Part 3.<\/strong> Lipids<\/a>\r\n<ul>\r\n \t<li><a href=\"#3.3a\">Triglycerides<\/a><\/li>\r\n \t<li><a href=\"#3.3b\">Phospholipids<\/a><\/li>\r\n \t<li><a href=\"#3.3c\">Steroids<\/a><\/li>\r\n<\/ul>\r\n<a href=\"#3.4\"><strong>Part 4.<\/strong> Proteins<\/a>\r\n<ul>\r\n \t<li><a href=\"#3.4a\">Microstructure of proteins<\/a><\/li>\r\n \t<li><a href=\"#3.4b\">Shape of proteins<\/a><\/li>\r\n \t<li><a href=\"#3.4c\">Functions of proteins<\/a><\/li>\r\n<\/ul>\r\n<a href=\"#3.5\"><strong>Part 5.<\/strong> Nucleotides and nucleic acids<\/a>\r\n<ul>\r\n \t<li><a href=\"#3.5a\">Adenosine triphosphate (ATP)<\/a><\/li>\r\n \t<li><a href=\"#3.5b\">Nucleic acids<\/a>\r\n<ul>\r\n \t<li>DNA<\/li>\r\n \t<li>RNA<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h2><a href=\"#p\">Practice Questions<\/a><\/h2>\r\n<\/div>\r\n<div class=\"textbox textbox--learning-objectives\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\"><strong>Learning Objectives<\/strong><\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nAt the end of this unit, you should be able to:\r\n<p class=\"hanging-indent\"><strong>I.<\/strong> Describe the chemistry of carbon.<\/p>\r\n<p class=\"hanging-indent\"><strong>II<\/strong><strong>.<\/strong> Describe the structure and function of carbohydrates.<\/p>\r\n<p class=\"hanging-indent\"><strong>III<\/strong><strong>.<\/strong> Describe the structure and function of lipids.<\/p>\r\n<p class=\"hanging-indent\"><strong>IV<\/strong><strong>.<\/strong> Describe the structure and function of proteins.<\/p>\r\n<p class=\"hanging-indent\"><strong>V.<\/strong> Describe the structure and function of nucleic acids.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox textbox--learning-objectives\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\"><strong>Learning Objectives and Guiding Questions<\/strong><\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nAt the end of this unit, you should be able to complete all the following tasks, including answering the guiding questions associated with each task.\r\n<p class=\"hanging-indent\"><strong>I.<\/strong> Describe the chemistry of carbon.<\/p>\r\n\r\n<ol>\r\n \t<li>Identify the number of covalent bonds carbon can form.<\/li>\r\n \t<li>Define the term \u201chydrocarbon chain\u201d.<\/li>\r\n \t<li>Define the term \u201cfunctional group\u201d, and identify five examples that are important in human physiology.<\/li>\r\n<\/ol>\r\n<p class=\"hanging-indent\"><strong>II<\/strong><strong>.<\/strong> Describe the structure and function of carbohydrates.<\/p>\r\n\r\n<ol>\r\n \t<li>Specify the three chemical elements of which carbohydrate molecules consist, and their relative (approximate) proportions in a typical carbohydrate molecule.<\/li>\r\n \t<li>Refer to the chemical structure of carbohydrates and the chemical properties of water to explain why carbohydrates are generally hydrophilic (soluble in water).<\/li>\r\n \t<li>Carbohydrate molecules can be grouped based on how many monomers they contain. For each of the three main size groups of carbohydrate:\r\n<ul>\r\n \t<li>Name and define the group (based on the number of monomers it contains)<\/li>\r\n \t<li>Name at least three specific examples of each group<\/li>\r\n \t<li>Briefly describe at least one major function in the human body of each group<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ol>\r\n<p class=\"hanging-indent\"><strong>III<\/strong><strong>.<\/strong> Describe the structure and function of lipids.<\/p>\r\n\r\n<ol>\r\n \t<li>Specify the major elements of lipid molecules.<\/li>\r\n \t<li>Specify the chemical elements of which lipid molecules typically consist, and their relative (approximate) proportions in a typical lipid molecule.<\/li>\r\n \t<li>Describe the following for triglycerides.\r\n<ul>\r\n \t<li>Using an annotated diagram, describe the main structural components<\/li>\r\n \t<li>Describe their primary function in the human body<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Describe the following for phospholipids.\r\n<ul>\r\n \t<li>Using an annotated diagram, describe the main structural components and distinguish between the polar head and non-polar tail ends<\/li>\r\n \t<li>Describe their primary function in the human body<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Describe the following for steroids.\r\n<ul>\r\n \t<li>Describe the main structural components<\/li>\r\n \t<li>Describe their primary function in the human body<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Refer to the chemical structure of lipids and the chemical properties of water to explain why lipids are generally insoluble in water.<\/li>\r\n \t<li>Describe and clearly distinguish between the physical and chemical characteristics of:\r\n<ul>\r\n \t<li>Saturated fats and unsaturated fats<\/li>\r\n \t<li>Monounsaturated fats and polyunsaturated fats<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ol>\r\n<p class=\"hanging-indent\"><strong>IV<\/strong><strong>.<\/strong> Describe the structure and function of proteins.<\/p>\r\n\r\n<ol>\r\n \t<li>Specify the chemical elements that make up protein molecules.<\/li>\r\n \t<li>Use an annotated diagram to show the structure of a generic amino acid.<\/li>\r\n \t<li>For each of the four levels of structure of a protein molecule:\r\n<ul>\r\n \t<li>Name the structural level.<\/li>\r\n \t<li>Define the structural level.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Describe, using examples, eight major functional groups of proteins.<\/li>\r\n \t<li>For each major functional group of proteins:\r\n<ul>\r\n \t<li>Briefly describe the major function in the human body.<\/li>\r\n \t<li>Name one protein that is representative of each group.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ol>\r\n<p class=\"hanging-indent\"><strong>V.<\/strong> Describe the structure and function of nucleic acids.<\/p>\r\n\r\n<ol>\r\n \t<li>Specify the chemical elements that make up nucleotides.<\/li>\r\n \t<li>Draw an annotated diagram to show the general structure of a generic nucleoside and a generic nucleotide.<\/li>\r\n \t<li>For adenosine triphosphate (ATP), describe its:\r\n<ul>\r\n \t<li>Chemical structure.<\/li>\r\n \t<li>Function in cells.<\/li>\r\n \t<li>Important chemical characteristics that allow it to perform its function.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>Draw two annotated diagrams to compare and contrast the overall structure of the two major nucleic acids found in human cells. In your diagrams, be sure to include the three main structural components of individual nucleotides.<\/li>\r\n \t<li>Compare and contrast the structure of RNA and DNA. For both molecules, identify:\r\n<ul>\r\n \t<li>The name and general structure of the monomers they consist of.<\/li>\r\n \t<li>The specific nitrogenous bases present in each.<\/li>\r\n \t<li>The one major structural difference between a molecule of RNA and a molecule of DNA.<\/li>\r\n \t<li>The type of bond holding the dual strands of DNA together.<\/li>\r\n \t<li>The main function in human cells.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<p style=\"text-align: justify\">Organic compounds typically consist of groups of carbon atoms covalently bonded to hydrogen, usually oxygen, and often other elements as well. Created by living things, they are found throughout the world, in soils and seas, commercial products, and every cell of the human body. The four types most important to human structure and function are carbohydrates, lipids, proteins, and nucleotides. Before exploring these compounds, you need to first understand the chemistry of carbon.<\/p>\r\n\r\n<h2 style=\"text-align: justify\"><strong><a id=\"3.1\"><\/a>Part 1. The Chemistry of Carbon<\/strong><\/h2>\r\n<p style=\"text-align: justify\">What makes [pb_glossary id=\"2065\"]organic compounds[\/pb_glossary] ubiquitous is the chemistry of their carbon core. Recall that carbon atoms have four [pb_glossary id=\"2073\"]electrons[\/pb_glossary] in their [pb_glossary id=\"2090\"]valence shell[\/pb_glossary], and that the octet rule dictates that atoms tend to react in such a way as to complete their valence shell with eight electrons. Carbon atoms do not complete their valence shells by donating or accepting four electrons. Instead, they readily share electrons via [pb_glossary id=\"2098\"]covalent bonds[\/pb_glossary].<\/p>\r\n<p style=\"text-align: justify\">Commonly, carbon atoms share with other carbon atoms, often forming a long carbon chain referred to as a carbon skeleton. It is also possible for carbon atoms to form more than one covalent bond with one another, and can form double bonds and triple bonds.<\/p>\r\n<p style=\"text-align: justify\">In organic compounds, carbon atoms can be found to share electrons with hydrogen. Carbon and hydrogen groupings are called [pb_glossary id=\"2145\"]hydrocarbons[\/pb_glossary]. If you study the figures of organic compounds in the remainder of this chapter, you will see several with chains of hydrocarbons in one region of the compound.<\/p>\r\n<p style=\"text-align: justify\">Carbon may share electrons with oxygen or nitrogen or other atoms in a particular region of an organic compound. Moreover, the atoms to which carbon atoms bond may also be part of a functional group. A <strong>[pb_glossary id=\"2146\"]functional group[\/pb_glossary]<\/strong> is a group of atoms linked by strong covalent bonds and tending to function in chemical reactions as a single unit. You can think of functional groups as tightly knit \u201ccliques\u201d whose members are unlikely to be parted. Five functional groups are important in human physiology; these are the [pb_glossary id=\"2125\"]hydroxyl[\/pb_glossary], [pb_glossary id=\"2147\"]carboxyl[\/pb_glossary], [pb_glossary id=\"2148\"]amino[\/pb_glossary], [pb_glossary id=\"2149\"]methyl[\/pb_glossary] and [pb_glossary id=\"2150\"]phosphate[\/pb_glossary] groups (Table 1).<\/p>\r\n\r\n<table style=\"border-collapse: collapse;width: 100%;height: 84px\" border=\"0\"><caption>Table 1: Functional Groups Important in Human Physiology<\/caption>\r\n<tbody>\r\n<tr style=\"height: 14px\">\r\n<th style=\"width: 16.9872%;height: 14px\" scope=\"col\"><strong>Functional Group<\/strong><\/th>\r\n<th style=\"width: 16.6666%;height: 14px\" scope=\"col\"><strong>Chemical formula<\/strong><\/th>\r\n<th style=\"width: 66.1859%;height: 14px\" scope=\"col\"><strong>Importance<\/strong><\/th>\r\n<\/tr>\r\n<tr style=\"height: 14px\">\r\n<td style=\"width: 16.9872%;height: 14px\">Hydroxyl<\/td>\r\n<td style=\"width: 16.6666%;height: 14px\">-OH<\/td>\r\n<td style=\"width: 66.1859%;height: 14px\">Polar group. Components of all four major classes of organic compounds discussed in this chapter.\u00a0 Involved in dehydration synthesis and hydrolysis reactions, and hydrogen bonding.<\/td>\r\n<\/tr>\r\n<tr style=\"height: 14px\">\r\n<td style=\"width: 16.9872%;height: 14px\">Carboxyl<\/td>\r\n<td style=\"width: 16.6666%;height: 14px\">-COOH<\/td>\r\n<td style=\"width: 66.1859%;height: 14px\">A component of the organic acids discussed in this chapter.<\/td>\r\n<\/tr>\r\n<tr style=\"height: 14px\">\r\n<td style=\"width: 16.9872%;height: 14px\">Amino<\/td>\r\n<td style=\"width: 16.6666%;height: 14px\">-NH<sub>2<\/sub><\/td>\r\n<td style=\"width: 66.1859%;height: 14px\">A component of all amino acids.<\/td>\r\n<\/tr>\r\n<tr style=\"height: 14px\">\r\n<td style=\"width: 16.9872%;height: 14px\">Methyl<\/td>\r\n<td style=\"width: 16.6666%;height: 14px\">-CH<sub>3<\/sub><\/td>\r\n<td style=\"width: 66.1859%;height: 14px\">A component of all fatty acids.<\/td>\r\n<\/tr>\r\n<tr style=\"height: 14px\">\r\n<td style=\"width: 16.9872%;height: 14px\">Phosphate<\/td>\r\n<td style=\"width: 16.6666%;height: 14px\">-PO<sub>4<\/sub><sup>2-<\/sup><\/td>\r\n<td style=\"width: 66.1859%;height: 14px\">A component of all phospholipids and nucleotides.<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<p style=\"text-align: justify\">Carbon\u2019s affinity for covalent bonding means that many distinct and relatively stable organic molecules nevertheless readily form larger, more complex molecules. Any large molecule is referred to as <strong>[pb_glossary id=\"2151\"]macromolecule[\/pb_glossary]<\/strong> (macro- = \u201clarge\u201d), and the organic compounds in this section all fit this description. However, some macromolecules are made up of several \u201ccopies\u201d of single units called [pb_glossary id=\"2152\"]monomer[\/pb_glossary] (mono- = \u201cone\u201d; -mer = \u201cpart\u201d). Like beads in a long necklace, these monomers link by covalent bonds to form long polymers (poly- = \u201cmany\u201d). There are many examples of monomers and [pb_glossary id=\"2153\"]polymers[\/pb_glossary] among the organic compounds.<\/p>\r\n<p style=\"text-align: justify\">Monomers form polymers by engaging in [pb_glossary id=\"2114\"]dehydration synthesis[\/pb_glossary] (Figure 1). As was noted earlier, this reaction results in the release of a molecule of water. Each monomer contributes: One gives up a hydrogen atom (H) and the other gives up a [pb_glossary id=\"2125\"]hydroxyl[\/pb_glossary] group (OH). Polymers are split into monomers by [pb_glossary id=\"2115\"]hydrolysis[\/pb_glossary] (-lysis = \u201crupture\u201d). The bonds between their monomers are broken, via the donation of a molecule of water, which contributes a hydrogen atom to one monomer and a hydroxyl group to the other.<\/p>\r\n\r\n<h2 style=\"text-align: justify\"><strong><a id=\"3.2\"><\/a>Part 2. Carbohydrates<\/strong><\/h2>\r\n<p style=\"text-align: justify\">A [pb_glossary id=\"2154\"]carbohydrate[\/pb_glossary] is a molecule composed of carbon, hydrogen, and oxygen; in most carbohydrates, hydrogen and oxygen are found in the same two-to-one relative proportions they have in water. In fact, the chemical formula for a \u201cgeneric\u201d molecule of carbohydrate is (CH<sub>2<\/sub>O)<sub><em>n<\/em><\/sub>. The structure also contains several hydroxyl groups, which makes carbohydrates [pb_glossary id=\"2100\"]polar[\/pb_glossary] in terms of chemical nature.<\/p>\r\n<p style=\"text-align: justify\">Carbohydrates are also referred to as saccharides, a word meaning \u201csugars.\u201d. Three forms are important in the body. [pb_glossary id=\"2155\"]Monosaccharides[\/pb_glossary] are the [pb_glossary id=\"2152\"]monomers[\/pb_glossary] of carbohydrates. Disaccharides (di- = \u201ctwo\u201d) are made up of two monomers. [pb_glossary id=\"2157\"]Polysaccharides[\/pb_glossary] are the [pb_glossary id=\"2153\"]polymers[\/pb_glossary], and can consist of hundreds to thousands of monomers.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"695\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image2-3.png\" alt=\"image\" width=\"695\" height=\"548\" \/> <strong>Figure 1. Five Important Monosaccharides.<\/strong> Different groups of monosaccharides are defined by the number of carbon atoms in their molecular structure. In the examples shown, the hexoses each contain six carbon atoms in their molecular structure, whereas the pentoses each contain five carbon atoms.[\/caption]\r\n<h5 style=\"text-align: justify\"><a id=\"3.2a\"><\/a><strong>Monosaccharides<\/strong><\/h5>\r\n<p style=\"text-align: justify\">A monosaccharide is a monomer of carbohydrates. Five monosaccharides are important in the body. Three of these are the hexose sugars, so called because they each contain six atoms of carbon. These are [pb_glossary id=\"2070\"]glucose[\/pb_glossary], fructose, and galactose (Figure 1a). The remaining monosaccharides are the two pentose sugars, each of which contains five atoms of carbon: ribose and deoxyribose (Figure 1b).<\/p>\r\n\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.2b\"><\/a>Disaccharides<\/strong><\/h5>\r\n<p style=\"text-align: justify\">A [pb_glossary id=\"2156\"]disaccharide[\/pb_glossary] is a pair of monosaccharides. Disaccharides are formed via [pb_glossary id=\"2114\"]dehydration synthesis[\/pb_glossary], and the bond linking them is referred to as a glycosidic bond (glyco- = \u201csugar\u201d). Three disaccharides are important to humans. These are sucrose, commonly referred to as table sugar; lactose, or milk sugar; and maltose, or malt sugar (Figure 2). As you can tell from their common names, you consume these in your diet; however, your body cannot use them directly. Instead, in the digestive tract, they are split into their component [pb_glossary id=\"2155\"]monosaccharides[\/pb_glossary] via [pb_glossary id=\"2115\"]hydrolysis[\/pb_glossary].<\/p>\r\n&nbsp;\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"633\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image3-3.png\" alt=\"image\" width=\"633\" height=\"1047\" \/> <strong>Figure 2. Three Important Disaccharides.<\/strong> All three important disaccharides are formed by dehydration synthesis.[\/caption]\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.2c\"><\/a>Polysaccharides<\/strong><\/h5>\r\n<p style=\"text-align: justify\">Polysaccharides can contain a few to a thousand or more monosaccharides. Three are important to the body (Figure 3):<\/p>\r\n\r\n<ul>\r\n \t<li style=\"text-align: justify\">Starches are polymers of glucose. They occur in long chains called amylose or branched chains called amylopectin, both of which are stored in plant-based foods and are relatively easy to digest.<\/li>\r\n \t<li style=\"text-align: justify\">[pb_glossary id=\"2158\"]Glycogen[\/pb_glossary] is also a polymer of glucose, but it is stored in the tissues of animals, especially in the muscles and liver. It is not considered a dietary carbohydrate because very little [pb_glossary id=\"2158\"]glycogen[\/pb_glossary] remains in animal tissues after slaughter; however, the human body stores excess glucose as glycogen, again, in the muscles and liver.<\/li>\r\n \t<li style=\"text-align: justify\">Cellulose, a polysaccharide made of glucose that is the primary component of the cell wall of green plants, is the component of plant food referred to as \u201cfibre\u201d. In humans, cellulose\/fibre is not digestible; however, dietary fibre has many health benefits. It helps you feel full so you eat less, it promotes a healthy digestive tract, and a diet high in fibre is thought to reduce the risk of heart disease and possibly some forms of cancer.<\/li>\r\n<\/ul>\r\n[caption id=\"\" align=\"alignnone\" width=\"1574\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image4-3.png\" alt=\"image\" width=\"1574\" height=\"535\" \/> <strong>Figure 3. Three Important Polysaccharides.<\/strong> Three important polysaccharides are starches, glycogen, and fibre.[\/caption]\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.2d\"><\/a>Functions of Carbohydrates<\/strong><\/h5>\r\n<p style=\"text-align: justify\">The body obtains carbohydrates from plant-based foods. Grains, fruits, and legumes and other vegetables provide most of the carbohydrates in the human diet, although lactose is found in dairy products. Polysaccharides such as starch, and various monosaccharides and disaccharides play a role as a primary energy source, especially glucose which is the main monosaccharide used in the body. Short chains of saccharides can also be used to form the [pb_glossary id=\"2159\"]glycocalyx[\/pb_glossary] (described in a later unit). The body is also capable of storing [pb_glossary id=\"2070\"]glucose[\/pb_glossary] in the body in the form of [pb_glossary id=\"2158\"]glycogen[\/pb_glossary] (a polysaccharide).<\/p>\r\nFinally, pentose sugars are critical structural components of [pb_glossary id=\"2074\"]ATP[\/pb_glossary] and the nucleotides that make up RNA and DNA.\r\n<h2 style=\"text-align: justify\"><strong><a id=\"3.3\"><\/a>Part 3. Lipids<\/strong><\/h2>\r\n<p style=\"text-align: justify\">A <strong>[pb_glossary id=\"2161\"]lipid[\/pb_glossary]<\/strong> is one of a highly diverse group of compounds made up mostly of hydrocarbons. The few oxygen atoms they contain are often at the periphery of the molecule. Their nonpolar hydrocarbons make all lipids hydrophobic. In water, lipids do not form a true [pb_glossary id=\"2110\"]solution[\/pb_glossary], but they may form an [pb_glossary id=\"2162\"]emulsion[\/pb_glossary], which is the term for a mixture of solutions that do not mix well.<\/p>\r\n\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.3a\"><\/a>Triglycerides<\/strong><\/h5>\r\n<p style=\"text-align: justify\">A triglyceride is one of the most common dietary lipid groups, and the type found most abundantly in body tissues. This [pb_glossary id=\"2063\"]compound[\/pb_glossary], which is commonly referred to as a fat, is formed by covalent bonding between two types of molecules (Figure 4):<\/p>\r\n\r\n<ul>\r\n \t<li>A [pb_glossary id=\"2163\"]glycerol[\/pb_glossary] backbone consists of three carbon atoms, each bonded to a hydroxyl group.<\/li>\r\n \t<li>Three [pb_glossary id=\"2164\"]fatty acids[\/pb_glossary], long chains of hydrocarbons with a carboxyl group and a methyl group at opposite ends, extend from each of the carbons of the glycerol. These hydrocarbon chains are formed with nonpolar bonds, making them hydrophobic in terms of chemical nature.<\/li>\r\n<\/ul>\r\n<p style=\"text-align: justify\">Triglycerides form via [pb_glossary id=\"2114\"]dehydration synthesis[\/pb_glossary]. Glycerol gives up hydrogen atoms from its hydroxyl groups at each bond, and the carboxyl group on each fatty acid chain gives up a hydroxyl group. A total of three water molecules are thereby released.<\/p>\r\n<p style=\"text-align: justify\">[pb_glossary id=\"2164\"]Fatty acid[\/pb_glossary] chains that have no double carbon bonds anywhere along their length and therefore contain the maximum number of hydrogen atoms are called saturated fatty acids. These straight, rigid chains pack tightly together and are solid or semi-solid at room temperature (Figure 5a). Butter and lard are examples, as is the fat found on a steak or in your own body. In contrast, fatty acids with one double carbon bond are kinked at that bond (Figure 5b). These monounsaturated fatty acids are therefore unable to pack together tightly, and are liquid at room temperature. Polyunsaturated fatty acids contain two or more double carbon bonds, and are also liquid at room temperature. Plant oils such as olive oil typically contain both mono- and polyunsaturated fatty acids.<\/p>\r\n&nbsp;\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"1668\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image5-3.png\" alt=\"image\" width=\"1668\" height=\"500\" \/> <strong>Figure 4. Triglycerides.<\/strong> Triglycerides are composed of three fatty acids attached to glycerol via dehydration synthesis. Notice that glycerol gives up individual hydrogen atoms, and the carboxyl groups on each fatty acid give up a hydroxyl group.[\/caption]\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"1467\"]<img style=\"color: #373d3f;font-weight: bold;font-size: 1em\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image6-3.png\" alt=\"image\" width=\"1467\" height=\"776\" \/> <strong>Figure 5. Fatty Acid Shapes.<\/strong> The level of saturation of a fatty acid affects its shape. (a) Saturated fatty acid chains are straight. (b) Unsaturated fatty acid chains are kinked.[\/caption]\r\n<p style=\"text-align: justify\">As a group, triglycerides are a major fuel source for the body and are used when glucose storages are low or during extended fasting conditions. Triglycerides also fuel long, slow physical activity such as gardening or hiking, and contribute a modest percentage of energy for vigorous physical activity. Dietary fat also assists the absorption and transport of the nonpolar fat-soluble [pb_glossary id=\"2165\"]vitamins[\/pb_glossary] A, D, E, and K. Additionally, stored body fat protects and cushions the body\u2019s bones and internal organs, and acts as insulation to retain body heat.<\/p>\r\n<p style=\"text-align: justify\">Fatty acids are also components of glycolipids, which are sugar-fat compounds found in the cell membrane. Lipoproteins are compounds in which the hydrophobic triglycerides are packaged in protein envelopes for transport in body fluids.<\/p>\r\n\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.3b\"><\/a>Phospholipids<\/strong><\/h5>\r\n<p style=\"text-align: justify\">As its name suggests, a <strong>[pb_glossary id=\"2166\"]phospholipid[\/pb_glossary]<\/strong> is a bond between the glycerol component of a lipid and a phosphorous molecule. In fact, phospholipids are similar in structure to triglycerides. However, instead of having three [pb_glossary id=\"2164\"]fatty acids[\/pb_glossary], a phospholipid is generated from a diglyceride, a [pb_glossary id=\"2163\"]glycerol[\/pb_glossary] with just two fatty acid chains (Figure 6). The third binding site on the glycerol is taken up by the phosphate group, which in turn is attached to a polar \u201chead\u201d region of the molecule. Recall that triglycerides are [pb_glossary id=\"2099\"]nonpolar[\/pb_glossary] and [pb_glossary id=\"2177\"]hydrophobic[\/pb_glossary]. This still holds for the fatty acid portion of a phospholipid compound. However, the head of a phospholipid contains charges on the [pb_glossary id=\"2150\"]phosphate[\/pb_glossary] groups, as well as on the nitrogen atom. These charges make the phospholipid head [pb_glossary id=\"2178\"]hydrophilic[\/pb_glossary]. Therefore, phospholipids are said to have hydrophobic tails, containing the neutral fatty acids, and hydrophilic heads, containing the charged phosphate groups and nitrogen atom. Phospholipids for the phospholipid bilayer, which is the basis of the structure of cell membranes.<\/p>\r\n\r\n\r\n[caption id=\"attachment_2031\" align=\"alignnone\" width=\"1024\"]<img class=\"wp-image-2031 size-large\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image7-2-from-Luis-1024x1024.png\" alt=\"\" width=\"1024\" height=\"1024\" \/> <strong>Figure 6. Other Important Lipids.<\/strong> (a) Phospholipids are composed of two fatty acids, glycerol, and a phosphate group. (b) Sterols are ring-shaped lipids. Shown here is cholesterol.[\/caption]\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.3c\"><\/a>Steroids<\/strong><\/h5>\r\n<p style=\"text-align: justify\">A [pb_glossary id=\"2168\"]steroid[\/pb_glossary] compound (referred to as a sterol) has as its foundation a set of four hydrocarbon rings bonded to a variety of other [pb_glossary id=\"2068\"]atoms[\/pb_glossary] and [pb_glossary id=\"2066\"]molecules[\/pb_glossary] (see Figure 6b). Although both plants and animals synthesize sterols, the type that makes the most important contribution to human structure and function is [pb_glossary id=\"2167\"]cholesterol[\/pb_glossary], which is synthesized by the liver in humans and animals and is also present in most animal-based foods. Like other lipids, cholesterol\u2019s hydrocarbons make it hydrophobic; however, it has a polar hydroxyl head that is hydrophilic. Cholesterol is an important component of [pb_glossary id=\"2169\"]bile[\/pb_glossary] acids, compounds that help [pb_glossary id=\"2170\"]emulsify[\/pb_glossary] dietary fats. Cholesterol is also a building block of many [pb_glossary id=\"2171\"]hormones[\/pb_glossary], signaling molecules that the body releases to regulate processes at distant sites.<\/p>\r\n\r\n<h2 style=\"text-align: justify\"><strong><a id=\"3.4\"><\/a>Part 4. Proteins<\/strong><\/h2>\r\n<p style=\"text-align: justify\">You might associate proteins with muscle tissue, but in fact, proteins are critical components of all tissues and organs. A <strong>[pb_glossary id=\"2069\"]protein[\/pb_glossary]<\/strong> is an organic molecule composed of [pb_glossary id=\"2179\"]amino acids[\/pb_glossary] linked by [pb_glossary id=\"2180\"]peptide bonds[\/pb_glossary]. Proteins include the keratin in the epidermis of skin that protects underlying tissues, the [pb_glossary id=\"2174\"]collagen[\/pb_glossary] found in the dermis of skin, in bones, and in the meninges that cover the brain and spinal cord. Proteins are also components of many of the body\u2019s functional chemicals, including digestive [pb_glossary id=\"2173\"]enzymes[\/pb_glossary] in the digestive tract, [pb_glossary id=\"2133\"]antibodies[\/pb_glossary], the [pb_glossary id=\"2172\"]neurotransmitters[\/pb_glossary] that [pb_glossary id=\"2181\"]neurons[\/pb_glossary] use to communicate with other cells, and the [pb_glossary id=\"2185\"]peptide[\/pb_glossary]-based hormones that regulate certain body functions (for instance, [pb_glossary id=\"2182\"]growth hormone[\/pb_glossary]). While carbohydrates and lipids are composed of [pb_glossary id=\"2183\"]hydrocarbons[\/pb_glossary] and oxygen, all proteins also contain nitrogen (N), and many contain sulfur (S), in addition to carbon, hydrogen, and oxygen, in varying ratios depending on the structure.<\/p>\r\n\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.4a\"><\/a>Microstructure of Proteins<\/strong><\/h5>\r\n<p style=\"text-align: justify\">Proteins are polymers made up of nitrogen-containing [pb_glossary id=\"2152\"]monomers[\/pb_glossary] called [pb_glossary id=\"2179\"]amino acids[\/pb_glossary]. An amino acid is a molecule composed of an amino group and a carboxyl group, together with a variable side chain. Just 20 different amino acids contribute to nearly all of the thousands of different proteins important in human structure and function. Body proteins contain a unique combination of a few dozen to a few hundred of these 20 amino acid monomers. All 20 of these amino acids share a similar structure (Figure 7). All consist of a central carbon atom to which the following are bonded:<\/p>\r\n\r\n<ul>\r\n \t<li>a hydrogen atom<\/li>\r\n \t<li>an [pb_glossary id=\"2184\"]alkaline[\/pb_glossary] (basic) amino group NH<sub>2<\/sub> (see Table 1)<\/li>\r\n \t<li>an acidic carboxyl group COOH (see Table 1)<\/li>\r\n \t<li>a variable group<\/li>\r\n<\/ul>\r\n<p style=\"text-align: justify\">Notice that all amino acids contain both an acid (the carboxyl group) and a base (the amino group) (amine = \u201cnitrogen-containing\u201d). What distinguishes the 20 amino acids from one another is their variable group, which is referred to one another is their variable group, which is referred to as a side chain or an R-group. This group can vary in size and can be [pb_glossary id=\"2100\"]polar[\/pb_glossary] or [pb_glossary id=\"2099\"]nonpolar[\/pb_glossary], giving each amino acid its unique characteristics.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"1040\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image8-2.png\" alt=\"image\" width=\"1040\" height=\"760\" \/> <strong>Figure 7. Structure of an Amino Acid.<\/strong> The side chain, designated \"R\", differs between specific amino acids and is composed of one or more hydrogen, carbon, oxygen, nitrogen, and\/or sulfur atoms.[\/caption]\r\n<p style=\"text-align: justify\">Amino acids join via dehydration synthesis to form protein polymers (Figure 8). The unique bond holding amino acids together is called a <strong>[pb_glossary id=\"2180\"]peptide bond[\/pb_glossary]<\/strong>. A peptide bond is a [pb_glossary id=\"2098\"]covalent bond[\/pb_glossary] between two amino acids that forms by dehydration synthesis. A [pb_glossary id=\"2185\"]peptide[\/pb_glossary], in fact, is a very short chain of amino acids. Strands containing fewer than about 100 amino acids are generally referred to as [pb_glossary id=\"2186\"]polypeptides[\/pb_glossary] rather than proteins.<\/p>\r\n<p style=\"text-align: justify\">The body is able to synthesize most of the amino acids from components of other molecules; however, some cannot be synthesized and have to be consumed in the diet. These are known as the essential amino acids.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"850\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image9-2.png\" alt=\"image\" width=\"850\" height=\"613\" \/> <strong>Figure 8. Peptide Bond.<\/strong> Different amino acids join together to form peptides, polypeptides, or proteins via dehydration synthesis. The bonds between the amino acids are peptide bonds.[\/caption]\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.4b\"><\/a>Shape of Proteins<\/strong><\/h5>\r\n<p style=\"text-align: justify\">A protein\u2019s shape is essential to its function, which is fundamentally determined by the sequence of amino acids of which it is made (Figure 9a). The sequence is called the primary structure of the protein.<\/p>\r\n<p style=\"text-align: justify\">Although some [pb_glossary id=\"2186\"]polypeptides[\/pb_glossary] exist as linear chains, most are twisted or folded into more complex secondary structures that form when bonding occurs between amino acids with different properties at different regions of the polypeptide.<\/p>\r\n<p style=\"text-align: justify\">The secondary structure of proteins further folds into a compact three-dimensional shape, referred to as the protein\u2019s tertiary structure (Figure 9c). Often, two or more separate polypeptides bond to form an even larger protein with a quaternary structure (Figure 9d). The polypeptide subunits forming a quaternary structure can be identical or different. For instance, [pb_glossary id=\"2187\"]hemoglobin[\/pb_glossary], the protein found in red blood cells is composed of four tertiary polypeptides, two of which are called alpha chains and two of which are called beta chains.<\/p>\r\n&nbsp;\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"1226\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image10.png\" alt=\"image\" width=\"1226\" height=\"1041\" \/> <strong>Figure 9. The Shape of Proteins.<\/strong> (a) The primary structure is the sequence of amino acids that make up the polypeptide chain. (b) The secondary structure, which can take the form of an alpha-helix or a beta-pleated sheet, is maintained by hydrogen bonds between amino acids in different regions of the original polypeptide strand. (c) The tertiary structure occurs as a result of further folding and bonding of the secondary structure. (d) The quaternary structure occurs as a result of interactions between two or more tertiary subunits. The example shown here is hemoglobin, a protein in red blood cells which transports oxygen to body tissues.[\/caption]\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.4c\"><\/a>Functions of Proteins<\/strong><\/h5>\r\n<p style=\"text-align: justify\">Proteins in the body have a variety of functions. Some proteins are used for <strong>movement<\/strong>, from muscle cell contraction ([pb_glossary id=\"2188\"]actin[\/pb_glossary] and [pb_glossary id=\"2189\"]myosin[\/pb_glossary]) down to intracellular transport (e.g. actin). Some proteins are also used to provide a structural framework or <strong>mechanical support<\/strong> of [pb_glossary id=\"2194\"]connective tissues[\/pb_glossary] (e.g. [pb_glossary id=\"2174\"]collagen[\/pb_glossary], keratin, [pb_glossary id=\"2195\"]elastin[\/pb_glossary]), individual cells (e.g. titin), and plasma membranes (e.g. spectrin, dystrophin). Some proteins called [pb_glossary id=\"2173\"]enzymes[\/pb_glossary], introduced earlier as protein catalysts, play a role in <strong>catalytic action<\/strong> (e.g., ATP synthase, etc.) to speed up chemical reactions in the body.<\/p>\r\n<p style=\"text-align: justify\">Some proteins are used to <strong>transport<\/strong> specific molecules (e.g. hormones or gases) or ions (e.g. iron or calcium) in blood. The [pb_glossary id=\"2187\"]hemoglobin[\/pb_glossary] proteins packed into red blood cells for example (Figure 9d) are used to transport the oxygen gas molecules from the lungs to other body cells. Others (e.g. albumin, hemoglobin) can help <strong>regulate body fluid pH<\/strong> by reversibly functioning as acids or bases, thus acting as [pb_glossary id=\"2190\"]buffers[\/pb_glossary]. Some proteins act as [pb_glossary id=\"2171\"]hormones[\/pb_glossary] to <strong>regulate metabolism<\/strong>, and are referred to as peptide hormones or protein hormones (e.g. [pb_glossary id=\"2192\"]insulin[\/pb_glossary], [pb_glossary id=\"2182\"]growth hormone[\/pb_glossary], [pb_glossary id=\"2191\"]oxytocin[\/pb_glossary]). Others are used to <strong>defend the body<\/strong> against foreign substances including invading [pb_glossary id=\"2193\"]pathogens[\/pb_glossary] and toxins (e.g. [pb_glossary id=\"2133\"]antibodies[\/pb_glossary], complement proteins). Finally, some proteins known as <strong>molecular chaperones<\/strong> (e.g., heat-shock proteins, etc.) are essential to the production of other proteins and the appropriate breakdown of damaged proteins.<\/p>\r\n<p style=\"text-align: justify\">As was noted earlier, the basic and acidic components enable proteins to function as [pb_glossary id=\"2190\"]buffers[\/pb_glossary] in maintaining acid\u2013base balance, but they also help regulate fluid\u2013electrolyte balance. Proteins attract fluid, and a healthy concentration of proteins in the blood, the cells, and the spaces between cells helps ensure a balance of fluids in these various \u201ccompartments.\u201d Moreover, proteins in the cell membrane help to transport electrolytes in and out of the cell, keeping these ions in a healthy balance. Like lipids, proteins can bind with carbohydrates. They can thereby produce glycoproteins or proteoglycans, both of which have many functions in the body.<\/p>\r\n<p style=\"text-align: justify\">The body can use proteins for energy when carbohydrate and fat intake is inadequate, and stores of glycogen and adipose tissue become depleted. However, since there is no storage site for protein except functional tissues, using protein for energy causes tissue breakdown, and results in body wasting.<\/p>\r\n\r\n<h2 style=\"text-align: justify\"><strong><a id=\"3.5\"><\/a>Part 5. Nucleotides and Nucleic Acids<\/strong><\/h2>\r\n<p style=\"text-align: justify\">The fourth type of organic compound important to human structure and function are the [pb_glossary id=\"2196\"]nucleotides[\/pb_glossary] (Figure 12). A nucleotide is one of a class of organic compounds composed of three subunits:<\/p>\r\n\r\n<ul>\r\n \t<li>one or more [pb_glossary id=\"2150\"]phosphate[\/pb_glossary] groups<\/li>\r\n \t<li>a pentose sugar: either deoxyribose or ribose<\/li>\r\n \t<li>a nitrogen-containing base: adenine, cytosine, guanine, thymine, or uracil<\/li>\r\n<\/ul>\r\n<p style=\"text-align: justify\">Nucleotides can be assembled into nucleic acids (DNA or RNA) or the energy compound adenosine triphosphate.<\/p>\r\n\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.5a\"><\/a>Adenosine triphosphate<\/strong><\/h5>\r\n<p style=\"text-align: justify\">The nucleotide [pb_glossary id=\"2074\"]adenosine triphosphate (ATP)[\/pb_glossary], is composed of a ribose sugar, an adenine base, and three phosphate groups (Figure 10). ATP is classified as a high energy compound because the two [pb_glossary id=\"2098\"]covalent bonds[\/pb_glossary] linking its three phosphates store a significant amount of [pb_glossary id=\"2197\"]potential energy[\/pb_glossary]. In the body, the energy released from these high energy bonds helps fuel the body\u2019s activities, from muscle contraction to the transport of substances in and out of cells to [pb_glossary id=\"2199\"]anabolic[\/pb_glossary] chemical reactions.<\/p>\r\n<p style=\"text-align: justify\">When a phosphate group is cleaved from ATP, the products are [pb_glossary id=\"2075\"]adenosine diphosphate (ADP)[\/pb_glossary] and<\/p>\r\n<p style=\"text-align: justify\">inorganic phosphate (Pi). This [pb_glossary id=\"2115\"]hydrolysis[\/pb_glossary] reaction can be written:<\/p>\r\n<p style=\"text-align: center\">ATP + H<sub>2<\/sub>O \u2192 ADP + Pi + energy<\/p>\r\n<p style=\"text-align: justify\">Removal of a second phosphate leaves adenosine monophosphate (AMP) and two phosphate groups. Again, these reactions also liberate the energy that had been stored in the phosphate-phosphate bonds. They are reversible, too, as when ADP undergoes phosphorylation.<strong> [pb_glossary id=\"2198\"]Phosphorylation[\/pb_glossary]<\/strong> is the addition of a phosphate group to an organic compound, in this case, resulting in ATP. In such cases, the same level of energy that had been released during hydrolysis must be reinvested to power [pb_glossary id=\"2114\"]dehydration synthesis[\/pb_glossary].<\/p>\r\n\r\n\r\n[caption id=\"attachment_1727\" align=\"alignnone\" width=\"512\"]<img class=\"wp-image-1727 size-full\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/Unit-2-ATP-diagram-fixed.png\" alt=\"\" width=\"512\" height=\"423\" \/> <strong>Figure 10. Structure of Adenosine Triphosphate (ATP).<\/strong> Adenosine is a nucleoside to which can be attached one (mono-), two (di-), or three (tri-) phosphate groups.[\/caption]\r\n<p style=\"text-align: justify\">Cells can also transfer a phosphate group from ATP to another organic compound. For example, when [pb_glossary id=\"2070\"]glucose[\/pb_glossary] first enters a cell, a phosphate group is transferred from ATP, forming glucose phosphate (C<sub>6<\/sub>H<sub>12<\/sub>O<sub>6<\/sub>\u2014P) and ADP. Once glucose is [pb_glossary id=\"2198\"]phosphorylated[\/pb_glossary] in this way, it can be stored as glycogen or metabolized for immediate energy.<\/p>\r\n\r\n<h5 style=\"text-align: justify\"><strong><a id=\"3.5b\"><\/a>Nucleic Acids<\/strong><\/h5>\r\n<p style=\"text-align: justify\">The nucleic acids differ in their type of pentose sugar. <strong>[pb_glossary id=\"2200\"]Deoxyribonucleic acid (DNA)[\/pb_glossary]<\/strong> is nucleotide that stores genetic information. DNA contains deoxyribose plus one phosphate group and one nitrogen-containing base. The bases for DNA can be adenine, cytosine, guanine, and thymine. <strong>[pb_glossary id=\"2201\"]Ribonucleic acid (RNA)[\/pb_glossary]<\/strong> is a ribose-containing nucleotide that helps manifest the genetic code as protein. RNA contains ribose, one phosphate group, and one nitrogen-containing base, but the bases for RNA are one of adenine, cytosine, guanine, and uracil. (Figure 11)<\/p>\r\n<p style=\"text-align: justify\">Bonds formed by dehydration synthesis between the pentose sugar of one nucleic acid monomer and the phosphate group of another form a \u201cbackbone,\u201d from which the components\u2019 nitrogen-containing bases protrude. In DNA, two such backbones attach at their protruding bases via [pb_glossary id=\"2103\"]hydrogen bonds[\/pb_glossary]. These twist to form a shape known as a double helix (Figure 12). The sequence of nitrogen-containing bases within a strand of DNA form the genes that act as a molecular code instructing cells in the assembly of amino acids into proteins. Humans have almost 22,000 genes in their DNA, locked up in the 46 [pb_glossary id=\"2202\"]chromosomes[\/pb_glossary] inside the nucleus of each cell (except red blood cells which lose their nuclei during development). These genes carry the genetic code to build one\u2019s body, and are unique for each individual except identical twins.<\/p>\r\n\r\n\r\n[caption id=\"attachment_1747\" align=\"alignnone\" width=\"1024\"]<img class=\"wp-image-1747 size-large\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/228_Nucleotides-01-1024x762.png\" alt=\"\" width=\"1024\" height=\"762\" \/> <strong>Figure 11. Nucleotides.<\/strong> (a) The building blocks of all nucleotides are one or more phosphate groups, a pentose sugar, and a nitrogen-containing base. (b) The nitrogen-containing bases of nucleotides. (c) The two pentose sugars of DNA and RNA.[\/caption]\r\n<p style=\"text-align: justify\">In contrast, RNA consists of a single strand of sugar-phosphate backbone studded with bases. Messenger RNA (mRNA) is created during protein synthesis to carry the genetic instructions from the DNA to the cell\u2019s protein manufacturing plants in the [pb_glossary id=\"2131\"]cytoplasm[\/pb_glossary], the [pb_glossary id=\"2203\"]ribosomes[\/pb_glossary].<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"804\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image13.png\" alt=\"image\" width=\"804\" height=\"1028\" \/> <strong>Figure 12. DNA.<\/strong> In the DNA double helix, two strands attach via hydrogen bonds between the bases of the component nucleotides.[\/caption]\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"142\"]<img src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image14.png\" alt=\"image\" width=\"142\" height=\"142\" \/> Watch <a href=\"https:\/\/youtu.be\/YO244P1e9QM\">this Amoeba Sisters video<\/a> to learn more about biomolecules! Direct link:\u00a0<a href=\"https:\/\/youtu.be\/YO244P1e9QM\">https:\/\/youtu.be\/YO244P1e9QM<\/a>[\/caption]\r\n\r\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\"><a id=\"p\"><\/a>Review Questions<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\n<strong>Part 1.<\/strong> <strong>Chemistry of carbon<\/strong>\r\n\r\n[h5p id=\"90\"]\r\n\r\n[h5p id=\"91\"]\r\n\r\n<strong>Part 2.<\/strong> <strong>Carbohydrates<\/strong>\r\n\r\n[h5p id=\"92\"]\r\n\r\n[h5p id=\"93\"]\r\n\r\n<strong>Part 3.<\/strong> <strong>Lipids<\/strong>\r\n\r\n[h5p id=\"94\"]\r\n\r\n[h5p id=\"95\"]\r\n\r\n<strong>Part 4.<\/strong> <strong>Proteins<\/strong>\r\n\r\n[h5p id=\"96\"]\r\n\r\n[h5p id=\"97\"]\r\n\r\n<strong>Part 5.<\/strong> <strong>Nucleotides and nucleic acids<\/strong>\r\n\r\n[h5p id=\"99\"]\r\n\r\n[h5p id=\"100\"]\r\n\r\n<\/div>\r\n<\/div>\r\n&nbsp;\r\n\r\n<\/div>","rendered":"<div class=\"unit-3:-biochemistry\">\n<div class=\"textbox shaded\">\n<p><strong>Unit outline<\/strong><\/p>\n<p><a href=\"#3.1\"><strong>Part 1.<\/strong> Chemistry of carbon<\/a><\/p>\n<p><a href=\"#3.2\"><strong>Part 2.<\/strong> Carbohydrates<\/a><\/p>\n<ul>\n<li><a href=\"#3.2a\">Monosaccharides<\/a><\/li>\n<li><a href=\"#3.2b\">Disaccharides<\/a><\/li>\n<li><a href=\"#3.2c\">Polysaccharides<\/a><\/li>\n<li><a href=\"#3.2d\">Functions of carbohydrates<\/a><\/li>\n<\/ul>\n<p><a href=\"#3.3\"><strong>Part 3.<\/strong> Lipids<\/a><\/p>\n<ul>\n<li><a href=\"#3.3a\">Triglycerides<\/a><\/li>\n<li><a href=\"#3.3b\">Phospholipids<\/a><\/li>\n<li><a href=\"#3.3c\">Steroids<\/a><\/li>\n<\/ul>\n<p><a href=\"#3.4\"><strong>Part 4.<\/strong> Proteins<\/a><\/p>\n<ul>\n<li><a href=\"#3.4a\">Microstructure of proteins<\/a><\/li>\n<li><a href=\"#3.4b\">Shape of proteins<\/a><\/li>\n<li><a href=\"#3.4c\">Functions of proteins<\/a><\/li>\n<\/ul>\n<p><a href=\"#3.5\"><strong>Part 5.<\/strong> Nucleotides and nucleic acids<\/a><\/p>\n<ul>\n<li><a href=\"#3.5a\">Adenosine triphosphate (ATP)<\/a><\/li>\n<li><a href=\"#3.5b\">Nucleic acids<\/a>\n<ul>\n<li>DNA<\/li>\n<li>RNA<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2><a href=\"#p\">Practice Questions<\/a><\/h2>\n<\/div>\n<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\"><strong>Learning Objectives<\/strong><\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>At the end of this unit, you should be able to:<\/p>\n<p class=\"hanging-indent\"><strong>I.<\/strong> Describe the chemistry of carbon.<\/p>\n<p class=\"hanging-indent\"><strong>II<\/strong><strong>.<\/strong> Describe the structure and function of carbohydrates.<\/p>\n<p class=\"hanging-indent\"><strong>III<\/strong><strong>.<\/strong> Describe the structure and function of lipids.<\/p>\n<p class=\"hanging-indent\"><strong>IV<\/strong><strong>.<\/strong> Describe the structure and function of proteins.<\/p>\n<p class=\"hanging-indent\"><strong>V.<\/strong> Describe the structure and function of nucleic acids.<\/p>\n<\/div>\n<\/div>\n<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\"><strong>Learning Objectives and Guiding Questions<\/strong><\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>At the end of this unit, you should be able to complete all the following tasks, including answering the guiding questions associated with each task.<\/p>\n<p class=\"hanging-indent\"><strong>I.<\/strong> Describe the chemistry of carbon.<\/p>\n<ol>\n<li>Identify the number of covalent bonds carbon can form.<\/li>\n<li>Define the term \u201chydrocarbon chain\u201d.<\/li>\n<li>Define the term \u201cfunctional group\u201d, and identify five examples that are important in human physiology.<\/li>\n<\/ol>\n<p class=\"hanging-indent\"><strong>II<\/strong><strong>.<\/strong> Describe the structure and function of carbohydrates.<\/p>\n<ol>\n<li>Specify the three chemical elements of which carbohydrate molecules consist, and their relative (approximate) proportions in a typical carbohydrate molecule.<\/li>\n<li>Refer to the chemical structure of carbohydrates and the chemical properties of water to explain why carbohydrates are generally hydrophilic (soluble in water).<\/li>\n<li>Carbohydrate molecules can be grouped based on how many monomers they contain. For each of the three main size groups of carbohydrate:\n<ul>\n<li>Name and define the group (based on the number of monomers it contains)<\/li>\n<li>Name at least three specific examples of each group<\/li>\n<li>Briefly describe at least one major function in the human body of each group<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<p class=\"hanging-indent\"><strong>III<\/strong><strong>.<\/strong> Describe the structure and function of lipids.<\/p>\n<ol>\n<li>Specify the major elements of lipid molecules.<\/li>\n<li>Specify the chemical elements of which lipid molecules typically consist, and their relative (approximate) proportions in a typical lipid molecule.<\/li>\n<li>Describe the following for triglycerides.\n<ul>\n<li>Using an annotated diagram, describe the main structural components<\/li>\n<li>Describe their primary function in the human body<\/li>\n<\/ul>\n<\/li>\n<li>Describe the following for phospholipids.\n<ul>\n<li>Using an annotated diagram, describe the main structural components and distinguish between the polar head and non-polar tail ends<\/li>\n<li>Describe their primary function in the human body<\/li>\n<\/ul>\n<\/li>\n<li>Describe the following for steroids.\n<ul>\n<li>Describe the main structural components<\/li>\n<li>Describe their primary function in the human body<\/li>\n<\/ul>\n<\/li>\n<li>Refer to the chemical structure of lipids and the chemical properties of water to explain why lipids are generally insoluble in water.<\/li>\n<li>Describe and clearly distinguish between the physical and chemical characteristics of:\n<ul>\n<li>Saturated fats and unsaturated fats<\/li>\n<li>Monounsaturated fats and polyunsaturated fats<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<p class=\"hanging-indent\"><strong>IV<\/strong><strong>.<\/strong> Describe the structure and function of proteins.<\/p>\n<ol>\n<li>Specify the chemical elements that make up protein molecules.<\/li>\n<li>Use an annotated diagram to show the structure of a generic amino acid.<\/li>\n<li>For each of the four levels of structure of a protein molecule:\n<ul>\n<li>Name the structural level.<\/li>\n<li>Define the structural level.<\/li>\n<\/ul>\n<\/li>\n<li>Describe, using examples, eight major functional groups of proteins.<\/li>\n<li>For each major functional group of proteins:\n<ul>\n<li>Briefly describe the major function in the human body.<\/li>\n<li>Name one protein that is representative of each group.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<p class=\"hanging-indent\"><strong>V.<\/strong> Describe the structure and function of nucleic acids.<\/p>\n<ol>\n<li>Specify the chemical elements that make up nucleotides.<\/li>\n<li>Draw an annotated diagram to show the general structure of a generic nucleoside and a generic nucleotide.<\/li>\n<li>For adenosine triphosphate (ATP), describe its:\n<ul>\n<li>Chemical structure.<\/li>\n<li>Function in cells.<\/li>\n<li>Important chemical characteristics that allow it to perform its function.<\/li>\n<\/ul>\n<\/li>\n<li>Draw two annotated diagrams to compare and contrast the overall structure of the two major nucleic acids found in human cells. In your diagrams, be sure to include the three main structural components of individual nucleotides.<\/li>\n<li>Compare and contrast the structure of RNA and DNA. For both molecules, identify:\n<ul>\n<li>The name and general structure of the monomers they consist of.<\/li>\n<li>The specific nitrogenous bases present in each.<\/li>\n<li>The one major structural difference between a molecule of RNA and a molecule of DNA.<\/li>\n<li>The type of bond holding the dual strands of DNA together.<\/li>\n<li>The main function in human cells.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<p style=\"text-align: justify\">Organic compounds typically consist of groups of carbon atoms covalently bonded to hydrogen, usually oxygen, and often other elements as well. Created by living things, they are found throughout the world, in soils and seas, commercial products, and every cell of the human body. The four types most important to human structure and function are carbohydrates, lipids, proteins, and nucleotides. Before exploring these compounds, you need to first understand the chemistry of carbon.<\/p>\n<h2 style=\"text-align: justify\"><strong><a id=\"3.1\"><\/a>Part 1. The Chemistry of Carbon<\/strong><\/h2>\n<p style=\"text-align: justify\">What makes <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2065\">organic compounds<\/a> ubiquitous is the chemistry of their carbon core. Recall that carbon atoms have four <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2073\">electrons<\/a> in their <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2090\">valence shell<\/a>, and that the octet rule dictates that atoms tend to react in such a way as to complete their valence shell with eight electrons. Carbon atoms do not complete their valence shells by donating or accepting four electrons. Instead, they readily share electrons via <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2098\">covalent bonds<\/a>.<\/p>\n<p style=\"text-align: justify\">Commonly, carbon atoms share with other carbon atoms, often forming a long carbon chain referred to as a carbon skeleton. It is also possible for carbon atoms to form more than one covalent bond with one another, and can form double bonds and triple bonds.<\/p>\n<p style=\"text-align: justify\">In organic compounds, carbon atoms can be found to share electrons with hydrogen. Carbon and hydrogen groupings are called <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2145\">hydrocarbons<\/a>. If you study the figures of organic compounds in the remainder of this chapter, you will see several with chains of hydrocarbons in one region of the compound.<\/p>\n<p style=\"text-align: justify\">Carbon may share electrons with oxygen or nitrogen or other atoms in a particular region of an organic compound. Moreover, the atoms to which carbon atoms bond may also be part of a functional group. A <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2146\">functional group<\/a><\/strong> is a group of atoms linked by strong covalent bonds and tending to function in chemical reactions as a single unit. You can think of functional groups as tightly knit \u201ccliques\u201d whose members are unlikely to be parted. Five functional groups are important in human physiology; these are the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2125\">hydroxyl<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2147\">carboxyl<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2148\">amino<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2149\">methyl<\/a> and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2150\">phosphate<\/a> groups (Table 1).<\/p>\n<table style=\"border-collapse: collapse;width: 100%;height: 84px\">\n<caption>Table 1: Functional Groups Important in Human Physiology<\/caption>\n<tbody>\n<tr style=\"height: 14px\">\n<th style=\"width: 16.9872%;height: 14px\" scope=\"col\"><strong>Functional Group<\/strong><\/th>\n<th style=\"width: 16.6666%;height: 14px\" scope=\"col\"><strong>Chemical formula<\/strong><\/th>\n<th style=\"width: 66.1859%;height: 14px\" scope=\"col\"><strong>Importance<\/strong><\/th>\n<\/tr>\n<tr style=\"height: 14px\">\n<td style=\"width: 16.9872%;height: 14px\">Hydroxyl<\/td>\n<td style=\"width: 16.6666%;height: 14px\">-OH<\/td>\n<td style=\"width: 66.1859%;height: 14px\">Polar group. Components of all four major classes of organic compounds discussed in this chapter.\u00a0 Involved in dehydration synthesis and hydrolysis reactions, and hydrogen bonding.<\/td>\n<\/tr>\n<tr style=\"height: 14px\">\n<td style=\"width: 16.9872%;height: 14px\">Carboxyl<\/td>\n<td style=\"width: 16.6666%;height: 14px\">-COOH<\/td>\n<td style=\"width: 66.1859%;height: 14px\">A component of the organic acids discussed in this chapter.<\/td>\n<\/tr>\n<tr style=\"height: 14px\">\n<td style=\"width: 16.9872%;height: 14px\">Amino<\/td>\n<td style=\"width: 16.6666%;height: 14px\">-NH<sub>2<\/sub><\/td>\n<td style=\"width: 66.1859%;height: 14px\">A component of all amino acids.<\/td>\n<\/tr>\n<tr style=\"height: 14px\">\n<td style=\"width: 16.9872%;height: 14px\">Methyl<\/td>\n<td style=\"width: 16.6666%;height: 14px\">-CH<sub>3<\/sub><\/td>\n<td style=\"width: 66.1859%;height: 14px\">A component of all fatty acids.<\/td>\n<\/tr>\n<tr style=\"height: 14px\">\n<td style=\"width: 16.9872%;height: 14px\">Phosphate<\/td>\n<td style=\"width: 16.6666%;height: 14px\">-PO<sub>4<\/sub><sup>2-<\/sup><\/td>\n<td style=\"width: 66.1859%;height: 14px\">A component of all phospholipids and nucleotides.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p style=\"text-align: justify\">Carbon\u2019s affinity for covalent bonding means that many distinct and relatively stable organic molecules nevertheless readily form larger, more complex molecules. Any large molecule is referred to as <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2151\">macromolecule<\/a><\/strong> (macro- = \u201clarge\u201d), and the organic compounds in this section all fit this description. However, some macromolecules are made up of several \u201ccopies\u201d of single units called <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2152\">monomer<\/a> (mono- = \u201cone\u201d; -mer = \u201cpart\u201d). Like beads in a long necklace, these monomers link by covalent bonds to form long polymers (poly- = \u201cmany\u201d). There are many examples of monomers and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2153\">polymers<\/a> among the organic compounds.<\/p>\n<p style=\"text-align: justify\">Monomers form polymers by engaging in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2114\">dehydration synthesis<\/a> (Figure 1). As was noted earlier, this reaction results in the release of a molecule of water. Each monomer contributes: One gives up a hydrogen atom (H) and the other gives up a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2125\">hydroxyl<\/a> group (OH). Polymers are split into monomers by <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2115\">hydrolysis<\/a> (-lysis = \u201crupture\u201d). The bonds between their monomers are broken, via the donation of a molecule of water, which contributes a hydrogen atom to one monomer and a hydroxyl group to the other.<\/p>\n<h2 style=\"text-align: justify\"><strong><a id=\"3.2\"><\/a>Part 2. Carbohydrates<\/strong><\/h2>\n<p style=\"text-align: justify\">A <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2154\">carbohydrate<\/a> is a molecule composed of carbon, hydrogen, and oxygen; in most carbohydrates, hydrogen and oxygen are found in the same two-to-one relative proportions they have in water. In fact, the chemical formula for a \u201cgeneric\u201d molecule of carbohydrate is (CH<sub>2<\/sub>O)<sub><em>n<\/em><\/sub>. The structure also contains several hydroxyl groups, which makes carbohydrates <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2100\">polar<\/a> in terms of chemical nature.<\/p>\n<p style=\"text-align: justify\">Carbohydrates are also referred to as saccharides, a word meaning \u201csugars.\u201d. Three forms are important in the body. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2155\">Monosaccharides<\/a> are the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2152\">monomers<\/a> of carbohydrates. Disaccharides (di- = \u201ctwo\u201d) are made up of two monomers. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2157\">Polysaccharides<\/a> are the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2153\">polymers<\/a>, and can consist of hundreds to thousands of monomers.<\/p>\n<figure style=\"width: 695px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image2-3.png\" alt=\"image\" width=\"695\" height=\"548\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 1. Five Important Monosaccharides.<\/strong> Different groups of monosaccharides are defined by the number of carbon atoms in their molecular structure. In the examples shown, the hexoses each contain six carbon atoms in their molecular structure, whereas the pentoses each contain five carbon atoms.<\/figcaption><\/figure>\n<h5 style=\"text-align: justify\"><a id=\"3.2a\"><\/a><strong>Monosaccharides<\/strong><\/h5>\n<p style=\"text-align: justify\">A monosaccharide is a monomer of carbohydrates. Five monosaccharides are important in the body. Three of these are the hexose sugars, so called because they each contain six atoms of carbon. These are <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2070\">glucose<\/a>, fructose, and galactose (Figure 1a). The remaining monosaccharides are the two pentose sugars, each of which contains five atoms of carbon: ribose and deoxyribose (Figure 1b).<\/p>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.2b\"><\/a>Disaccharides<\/strong><\/h5>\n<p style=\"text-align: justify\">A <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2156\">disaccharide<\/a> is a pair of monosaccharides. Disaccharides are formed via <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2114\">dehydration synthesis<\/a>, and the bond linking them is referred to as a glycosidic bond (glyco- = \u201csugar\u201d). Three disaccharides are important to humans. These are sucrose, commonly referred to as table sugar; lactose, or milk sugar; and maltose, or malt sugar (Figure 2). As you can tell from their common names, you consume these in your diet; however, your body cannot use them directly. Instead, in the digestive tract, they are split into their component <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2155\">monosaccharides<\/a> via <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2115\">hydrolysis<\/a>.<\/p>\n<p>&nbsp;<\/p>\n<figure style=\"width: 633px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image3-3.png\" alt=\"image\" width=\"633\" height=\"1047\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 2. Three Important Disaccharides.<\/strong> All three important disaccharides are formed by dehydration synthesis.<\/figcaption><\/figure>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.2c\"><\/a>Polysaccharides<\/strong><\/h5>\n<p style=\"text-align: justify\">Polysaccharides can contain a few to a thousand or more monosaccharides. Three are important to the body (Figure 3):<\/p>\n<ul>\n<li style=\"text-align: justify\">Starches are polymers of glucose. They occur in long chains called amylose or branched chains called amylopectin, both of which are stored in plant-based foods and are relatively easy to digest.<\/li>\n<li style=\"text-align: justify\"><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2158\">Glycogen<\/a> is also a polymer of glucose, but it is stored in the tissues of animals, especially in the muscles and liver. It is not considered a dietary carbohydrate because very little <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2158\">glycogen<\/a> remains in animal tissues after slaughter; however, the human body stores excess glucose as glycogen, again, in the muscles and liver.<\/li>\n<li style=\"text-align: justify\">Cellulose, a polysaccharide made of glucose that is the primary component of the cell wall of green plants, is the component of plant food referred to as \u201cfibre\u201d. In humans, cellulose\/fibre is not digestible; however, dietary fibre has many health benefits. It helps you feel full so you eat less, it promotes a healthy digestive tract, and a diet high in fibre is thought to reduce the risk of heart disease and possibly some forms of cancer.<\/li>\n<\/ul>\n<figure style=\"width: 1574px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image4-3.png\" alt=\"image\" width=\"1574\" height=\"535\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 3. Three Important Polysaccharides.<\/strong> Three important polysaccharides are starches, glycogen, and fibre.<\/figcaption><\/figure>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.2d\"><\/a>Functions of Carbohydrates<\/strong><\/h5>\n<p style=\"text-align: justify\">The body obtains carbohydrates from plant-based foods. Grains, fruits, and legumes and other vegetables provide most of the carbohydrates in the human diet, although lactose is found in dairy products. Polysaccharides such as starch, and various monosaccharides and disaccharides play a role as a primary energy source, especially glucose which is the main monosaccharide used in the body. Short chains of saccharides can also be used to form the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2159\">glycocalyx<\/a> (described in a later unit). The body is also capable of storing <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2070\">glucose<\/a> in the body in the form of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2158\">glycogen<\/a> (a polysaccharide).<\/p>\n<p>Finally, pentose sugars are critical structural components of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2074\">ATP<\/a> and the nucleotides that make up RNA and DNA.<\/p>\n<h2 style=\"text-align: justify\"><strong><a id=\"3.3\"><\/a>Part 3. Lipids<\/strong><\/h2>\n<p style=\"text-align: justify\">A <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2161\">lipid<\/a><\/strong> is one of a highly diverse group of compounds made up mostly of hydrocarbons. The few oxygen atoms they contain are often at the periphery of the molecule. Their nonpolar hydrocarbons make all lipids hydrophobic. In water, lipids do not form a true <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2110\">solution<\/a>, but they may form an <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2162\">emulsion<\/a>, which is the term for a mixture of solutions that do not mix well.<\/p>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.3a\"><\/a>Triglycerides<\/strong><\/h5>\n<p style=\"text-align: justify\">A triglyceride is one of the most common dietary lipid groups, and the type found most abundantly in body tissues. This <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2063\">compound<\/a>, which is commonly referred to as a fat, is formed by covalent bonding between two types of molecules (Figure 4):<\/p>\n<ul>\n<li>A <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2163\">glycerol<\/a> backbone consists of three carbon atoms, each bonded to a hydroxyl group.<\/li>\n<li>Three <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2164\">fatty acids<\/a>, long chains of hydrocarbons with a carboxyl group and a methyl group at opposite ends, extend from each of the carbons of the glycerol. These hydrocarbon chains are formed with nonpolar bonds, making them hydrophobic in terms of chemical nature.<\/li>\n<\/ul>\n<p style=\"text-align: justify\">Triglycerides form via <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2114\">dehydration synthesis<\/a>. Glycerol gives up hydrogen atoms from its hydroxyl groups at each bond, and the carboxyl group on each fatty acid chain gives up a hydroxyl group. A total of three water molecules are thereby released.<\/p>\n<p style=\"text-align: justify\"><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2164\">Fatty acid<\/a> chains that have no double carbon bonds anywhere along their length and therefore contain the maximum number of hydrogen atoms are called saturated fatty acids. These straight, rigid chains pack tightly together and are solid or semi-solid at room temperature (Figure 5a). Butter and lard are examples, as is the fat found on a steak or in your own body. In contrast, fatty acids with one double carbon bond are kinked at that bond (Figure 5b). These monounsaturated fatty acids are therefore unable to pack together tightly, and are liquid at room temperature. Polyunsaturated fatty acids contain two or more double carbon bonds, and are also liquid at room temperature. Plant oils such as olive oil typically contain both mono- and polyunsaturated fatty acids.<\/p>\n<p>&nbsp;<\/p>\n<figure style=\"width: 1668px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image5-3.png\" alt=\"image\" width=\"1668\" height=\"500\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 4. Triglycerides.<\/strong> Triglycerides are composed of three fatty acids attached to glycerol via dehydration synthesis. Notice that glycerol gives up individual hydrogen atoms, and the carboxyl groups on each fatty acid give up a hydroxyl group.<\/figcaption><\/figure>\n<figure style=\"width: 1467px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" style=\"color: #373d3f;font-weight: bold;font-size: 1em\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image6-3.png\" alt=\"image\" width=\"1467\" height=\"776\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 5. Fatty Acid Shapes.<\/strong> The level of saturation of a fatty acid affects its shape. (a) Saturated fatty acid chains are straight. (b) Unsaturated fatty acid chains are kinked.<\/figcaption><\/figure>\n<p style=\"text-align: justify\">As a group, triglycerides are a major fuel source for the body and are used when glucose storages are low or during extended fasting conditions. Triglycerides also fuel long, slow physical activity such as gardening or hiking, and contribute a modest percentage of energy for vigorous physical activity. Dietary fat also assists the absorption and transport of the nonpolar fat-soluble <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2165\">vitamins<\/a> A, D, E, and K. Additionally, stored body fat protects and cushions the body\u2019s bones and internal organs, and acts as insulation to retain body heat.<\/p>\n<p style=\"text-align: justify\">Fatty acids are also components of glycolipids, which are sugar-fat compounds found in the cell membrane. Lipoproteins are compounds in which the hydrophobic triglycerides are packaged in protein envelopes for transport in body fluids.<\/p>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.3b\"><\/a>Phospholipids<\/strong><\/h5>\n<p style=\"text-align: justify\">As its name suggests, a <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2166\">phospholipid<\/a><\/strong> is a bond between the glycerol component of a lipid and a phosphorous molecule. In fact, phospholipids are similar in structure to triglycerides. However, instead of having three <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2164\">fatty acids<\/a>, a phospholipid is generated from a diglyceride, a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2163\">glycerol<\/a> with just two fatty acid chains (Figure 6). The third binding site on the glycerol is taken up by the phosphate group, which in turn is attached to a polar \u201chead\u201d region of the molecule. Recall that triglycerides are <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2099\">nonpolar<\/a> and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2177\">hydrophobic<\/a>. This still holds for the fatty acid portion of a phospholipid compound. However, the head of a phospholipid contains charges on the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2150\">phosphate<\/a> groups, as well as on the nitrogen atom. These charges make the phospholipid head <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2178\">hydrophilic<\/a>. Therefore, phospholipids are said to have hydrophobic tails, containing the neutral fatty acids, and hydrophilic heads, containing the charged phosphate groups and nitrogen atom. Phospholipids for the phospholipid bilayer, which is the basis of the structure of cell membranes.<\/p>\n<figure id=\"attachment_2031\" aria-describedby=\"caption-attachment-2031\" style=\"width: 1024px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-2031 size-large\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image7-2-from-Luis-1024x1024.png\" alt=\"\" width=\"1024\" height=\"1024\" srcset=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image7-2-from-Luis-1024x1024.png 1024w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image7-2-from-Luis-300x300.png 300w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image7-2-from-Luis-150x150.png 150w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image7-2-from-Luis-768x767.png 768w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image7-2-from-Luis-65x65.png 65w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image7-2-from-Luis-225x225.png 225w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image7-2-from-Luis-350x350.png 350w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image7-2-from-Luis.png 1046w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-2031\" class=\"wp-caption-text\"><strong>Figure 6. Other Important Lipids.<\/strong> (a) Phospholipids are composed of two fatty acids, glycerol, and a phosphate group. (b) Sterols are ring-shaped lipids. Shown here is cholesterol.<\/figcaption><\/figure>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.3c\"><\/a>Steroids<\/strong><\/h5>\n<p style=\"text-align: justify\">A <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2168\">steroid<\/a> compound (referred to as a sterol) has as its foundation a set of four hydrocarbon rings bonded to a variety of other <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2068\">atoms<\/a> and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2066\">molecules<\/a> (see Figure 6b). Although both plants and animals synthesize sterols, the type that makes the most important contribution to human structure and function is <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2167\">cholesterol<\/a>, which is synthesized by the liver in humans and animals and is also present in most animal-based foods. Like other lipids, cholesterol\u2019s hydrocarbons make it hydrophobic; however, it has a polar hydroxyl head that is hydrophilic. Cholesterol is an important component of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2169\">bile<\/a> acids, compounds that help <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2170\">emulsify<\/a> dietary fats. Cholesterol is also a building block of many <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2171\">hormones<\/a>, signaling molecules that the body releases to regulate processes at distant sites.<\/p>\n<h2 style=\"text-align: justify\"><strong><a id=\"3.4\"><\/a>Part 4. Proteins<\/strong><\/h2>\n<p style=\"text-align: justify\">You might associate proteins with muscle tissue, but in fact, proteins are critical components of all tissues and organs. A <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2069\">protein<\/a><\/strong> is an organic molecule composed of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2179\">amino acids<\/a> linked by <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2180\">peptide bonds<\/a>. Proteins include the keratin in the epidermis of skin that protects underlying tissues, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2174\">collagen<\/a> found in the dermis of skin, in bones, and in the meninges that cover the brain and spinal cord. Proteins are also components of many of the body\u2019s functional chemicals, including digestive <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2173\">enzymes<\/a> in the digestive tract, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2133\">antibodies<\/a>, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2172\">neurotransmitters<\/a> that <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2181\">neurons<\/a> use to communicate with other cells, and the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2185\">peptide<\/a>-based hormones that regulate certain body functions (for instance, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2182\">growth hormone<\/a>). While carbohydrates and lipids are composed of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2183\">hydrocarbons<\/a> and oxygen, all proteins also contain nitrogen (N), and many contain sulfur (S), in addition to carbon, hydrogen, and oxygen, in varying ratios depending on the structure.<\/p>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.4a\"><\/a>Microstructure of Proteins<\/strong><\/h5>\n<p style=\"text-align: justify\">Proteins are polymers made up of nitrogen-containing <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2152\">monomers<\/a> called <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2179\">amino acids<\/a>. An amino acid is a molecule composed of an amino group and a carboxyl group, together with a variable side chain. Just 20 different amino acids contribute to nearly all of the thousands of different proteins important in human structure and function. Body proteins contain a unique combination of a few dozen to a few hundred of these 20 amino acid monomers. All 20 of these amino acids share a similar structure (Figure 7). All consist of a central carbon atom to which the following are bonded:<\/p>\n<ul>\n<li>a hydrogen atom<\/li>\n<li>an <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2184\">alkaline<\/a> (basic) amino group NH<sub>2<\/sub> (see Table 1)<\/li>\n<li>an acidic carboxyl group COOH (see Table 1)<\/li>\n<li>a variable group<\/li>\n<\/ul>\n<p style=\"text-align: justify\">Notice that all amino acids contain both an acid (the carboxyl group) and a base (the amino group) (amine = \u201cnitrogen-containing\u201d). What distinguishes the 20 amino acids from one another is their variable group, which is referred to one another is their variable group, which is referred to as a side chain or an R-group. This group can vary in size and can be <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2100\">polar<\/a> or <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2099\">nonpolar<\/a>, giving each amino acid its unique characteristics.<\/p>\n<figure style=\"width: 1040px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image8-2.png\" alt=\"image\" width=\"1040\" height=\"760\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 7. Structure of an Amino Acid.<\/strong> The side chain, designated &#8220;R&#8221;, differs between specific amino acids and is composed of one or more hydrogen, carbon, oxygen, nitrogen, and\/or sulfur atoms.<\/figcaption><\/figure>\n<p style=\"text-align: justify\">Amino acids join via dehydration synthesis to form protein polymers (Figure 8). The unique bond holding amino acids together is called a <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2180\">peptide bond<\/a><\/strong>. A peptide bond is a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2098\">covalent bond<\/a> between two amino acids that forms by dehydration synthesis. A <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2185\">peptide<\/a>, in fact, is a very short chain of amino acids. Strands containing fewer than about 100 amino acids are generally referred to as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2186\">polypeptides<\/a> rather than proteins.<\/p>\n<p style=\"text-align: justify\">The body is able to synthesize most of the amino acids from components of other molecules; however, some cannot be synthesized and have to be consumed in the diet. These are known as the essential amino acids.<\/p>\n<figure style=\"width: 850px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image9-2.png\" alt=\"image\" width=\"850\" height=\"613\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 8. Peptide Bond.<\/strong> Different amino acids join together to form peptides, polypeptides, or proteins via dehydration synthesis. The bonds between the amino acids are peptide bonds.<\/figcaption><\/figure>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.4b\"><\/a>Shape of Proteins<\/strong><\/h5>\n<p style=\"text-align: justify\">A protein\u2019s shape is essential to its function, which is fundamentally determined by the sequence of amino acids of which it is made (Figure 9a). The sequence is called the primary structure of the protein.<\/p>\n<p style=\"text-align: justify\">Although some <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2186\">polypeptides<\/a> exist as linear chains, most are twisted or folded into more complex secondary structures that form when bonding occurs between amino acids with different properties at different regions of the polypeptide.<\/p>\n<p style=\"text-align: justify\">The secondary structure of proteins further folds into a compact three-dimensional shape, referred to as the protein\u2019s tertiary structure (Figure 9c). Often, two or more separate polypeptides bond to form an even larger protein with a quaternary structure (Figure 9d). The polypeptide subunits forming a quaternary structure can be identical or different. For instance, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2187\">hemoglobin<\/a>, the protein found in red blood cells is composed of four tertiary polypeptides, two of which are called alpha chains and two of which are called beta chains.<\/p>\n<p>&nbsp;<\/p>\n<figure style=\"width: 1226px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image10.png\" alt=\"image\" width=\"1226\" height=\"1041\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 9. The Shape of Proteins.<\/strong> (a) The primary structure is the sequence of amino acids that make up the polypeptide chain. (b) The secondary structure, which can take the form of an alpha-helix or a beta-pleated sheet, is maintained by hydrogen bonds between amino acids in different regions of the original polypeptide strand. (c) The tertiary structure occurs as a result of further folding and bonding of the secondary structure. (d) The quaternary structure occurs as a result of interactions between two or more tertiary subunits. The example shown here is hemoglobin, a protein in red blood cells which transports oxygen to body tissues.<\/figcaption><\/figure>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.4c\"><\/a>Functions of Proteins<\/strong><\/h5>\n<p style=\"text-align: justify\">Proteins in the body have a variety of functions. Some proteins are used for <strong>movement<\/strong>, from muscle cell contraction (<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2188\">actin<\/a> and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2189\">myosin<\/a>) down to intracellular transport (e.g. actin). Some proteins are also used to provide a structural framework or <strong>mechanical support<\/strong> of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2194\">connective tissues<\/a> (e.g. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2174\">collagen<\/a>, keratin, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2195\">elastin<\/a>), individual cells (e.g. titin), and plasma membranes (e.g. spectrin, dystrophin). Some proteins called <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2173\">enzymes<\/a>, introduced earlier as protein catalysts, play a role in <strong>catalytic action<\/strong> (e.g., ATP synthase, etc.) to speed up chemical reactions in the body.<\/p>\n<p style=\"text-align: justify\">Some proteins are used to <strong>transport<\/strong> specific molecules (e.g. hormones or gases) or ions (e.g. iron or calcium) in blood. The <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2187\">hemoglobin<\/a> proteins packed into red blood cells for example (Figure 9d) are used to transport the oxygen gas molecules from the lungs to other body cells. Others (e.g. albumin, hemoglobin) can help <strong>regulate body fluid pH<\/strong> by reversibly functioning as acids or bases, thus acting as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2190\">buffers<\/a>. Some proteins act as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2171\">hormones<\/a> to <strong>regulate metabolism<\/strong>, and are referred to as peptide hormones or protein hormones (e.g. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2192\">insulin<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2182\">growth hormone<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2191\">oxytocin<\/a>). Others are used to <strong>defend the body<\/strong> against foreign substances including invading <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2193\">pathogens<\/a> and toxins (e.g. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2133\">antibodies<\/a>, complement proteins). Finally, some proteins known as <strong>molecular chaperones<\/strong> (e.g., heat-shock proteins, etc.) are essential to the production of other proteins and the appropriate breakdown of damaged proteins.<\/p>\n<p style=\"text-align: justify\">As was noted earlier, the basic and acidic components enable proteins to function as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2190\">buffers<\/a> in maintaining acid\u2013base balance, but they also help regulate fluid\u2013electrolyte balance. Proteins attract fluid, and a healthy concentration of proteins in the blood, the cells, and the spaces between cells helps ensure a balance of fluids in these various \u201ccompartments.\u201d Moreover, proteins in the cell membrane help to transport electrolytes in and out of the cell, keeping these ions in a healthy balance. Like lipids, proteins can bind with carbohydrates. They can thereby produce glycoproteins or proteoglycans, both of which have many functions in the body.<\/p>\n<p style=\"text-align: justify\">The body can use proteins for energy when carbohydrate and fat intake is inadequate, and stores of glycogen and adipose tissue become depleted. However, since there is no storage site for protein except functional tissues, using protein for energy causes tissue breakdown, and results in body wasting.<\/p>\n<h2 style=\"text-align: justify\"><strong><a id=\"3.5\"><\/a>Part 5. Nucleotides and Nucleic Acids<\/strong><\/h2>\n<p style=\"text-align: justify\">The fourth type of organic compound important to human structure and function are the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2196\">nucleotides<\/a> (Figure 12). A nucleotide is one of a class of organic compounds composed of three subunits:<\/p>\n<ul>\n<li>one or more <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2150\">phosphate<\/a> groups<\/li>\n<li>a pentose sugar: either deoxyribose or ribose<\/li>\n<li>a nitrogen-containing base: adenine, cytosine, guanine, thymine, or uracil<\/li>\n<\/ul>\n<p style=\"text-align: justify\">Nucleotides can be assembled into nucleic acids (DNA or RNA) or the energy compound adenosine triphosphate.<\/p>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.5a\"><\/a>Adenosine triphosphate<\/strong><\/h5>\n<p style=\"text-align: justify\">The nucleotide <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2074\">adenosine triphosphate (ATP)<\/a>, is composed of a ribose sugar, an adenine base, and three phosphate groups (Figure 10). ATP is classified as a high energy compound because the two <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2098\">covalent bonds<\/a> linking its three phosphates store a significant amount of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2197\">potential energy<\/a>. In the body, the energy released from these high energy bonds helps fuel the body\u2019s activities, from muscle contraction to the transport of substances in and out of cells to <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2199\">anabolic<\/a> chemical reactions.<\/p>\n<p style=\"text-align: justify\">When a phosphate group is cleaved from ATP, the products are <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2075\">adenosine diphosphate (ADP)<\/a> and<\/p>\n<p style=\"text-align: justify\">inorganic phosphate (Pi). This <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2115\">hydrolysis<\/a> reaction can be written:<\/p>\n<p style=\"text-align: center\">ATP + H<sub>2<\/sub>O \u2192 ADP + Pi + energy<\/p>\n<p style=\"text-align: justify\">Removal of a second phosphate leaves adenosine monophosphate (AMP) and two phosphate groups. Again, these reactions also liberate the energy that had been stored in the phosphate-phosphate bonds. They are reversible, too, as when ADP undergoes phosphorylation.<strong> <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2198\">Phosphorylation<\/a><\/strong> is the addition of a phosphate group to an organic compound, in this case, resulting in ATP. In such cases, the same level of energy that had been released during hydrolysis must be reinvested to power <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2114\">dehydration synthesis<\/a>.<\/p>\n<figure id=\"attachment_1727\" aria-describedby=\"caption-attachment-1727\" style=\"width: 512px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1727 size-full\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/Unit-2-ATP-diagram-fixed.png\" alt=\"\" width=\"512\" height=\"423\" srcset=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/Unit-2-ATP-diagram-fixed.png 512w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/Unit-2-ATP-diagram-fixed-300x248.png 300w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/Unit-2-ATP-diagram-fixed-65x54.png 65w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/Unit-2-ATP-diagram-fixed-225x186.png 225w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/Unit-2-ATP-diagram-fixed-350x289.png 350w\" sizes=\"auto, (max-width: 512px) 100vw, 512px\" \/><figcaption id=\"caption-attachment-1727\" class=\"wp-caption-text\"><strong>Figure 10. Structure of Adenosine Triphosphate (ATP).<\/strong> Adenosine is a nucleoside to which can be attached one (mono-), two (di-), or three (tri-) phosphate groups.<\/figcaption><\/figure>\n<p style=\"text-align: justify\">Cells can also transfer a phosphate group from ATP to another organic compound. For example, when <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2070\">glucose<\/a> first enters a cell, a phosphate group is transferred from ATP, forming glucose phosphate (C<sub>6<\/sub>H<sub>12<\/sub>O<sub>6<\/sub>\u2014P) and ADP. Once glucose is <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2198\">phosphorylated<\/a> in this way, it can be stored as glycogen or metabolized for immediate energy.<\/p>\n<h5 style=\"text-align: justify\"><strong><a id=\"3.5b\"><\/a>Nucleic Acids<\/strong><\/h5>\n<p style=\"text-align: justify\">The nucleic acids differ in their type of pentose sugar. <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2200\">Deoxyribonucleic acid (DNA)<\/a><\/strong> is nucleotide that stores genetic information. DNA contains deoxyribose plus one phosphate group and one nitrogen-containing base. The bases for DNA can be adenine, cytosine, guanine, and thymine. <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2201\">Ribonucleic acid (RNA)<\/a><\/strong> is a ribose-containing nucleotide that helps manifest the genetic code as protein. RNA contains ribose, one phosphate group, and one nitrogen-containing base, but the bases for RNA are one of adenine, cytosine, guanine, and uracil. (Figure 11)<\/p>\n<p style=\"text-align: justify\">Bonds formed by dehydration synthesis between the pentose sugar of one nucleic acid monomer and the phosphate group of another form a \u201cbackbone,\u201d from which the components\u2019 nitrogen-containing bases protrude. In DNA, two such backbones attach at their protruding bases via <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2103\">hydrogen bonds<\/a>. These twist to form a shape known as a double helix (Figure 12). The sequence of nitrogen-containing bases within a strand of DNA form the genes that act as a molecular code instructing cells in the assembly of amino acids into proteins. Humans have almost 22,000 genes in their DNA, locked up in the 46 <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2202\">chromosomes<\/a> inside the nucleus of each cell (except red blood cells which lose their nuclei during development). These genes carry the genetic code to build one\u2019s body, and are unique for each individual except identical twins.<\/p>\n<figure id=\"attachment_1747\" aria-describedby=\"caption-attachment-1747\" style=\"width: 1024px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1747 size-large\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/228_Nucleotides-01-1024x762.png\" alt=\"\" width=\"1024\" height=\"762\" srcset=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/228_Nucleotides-01-1024x762.png 1024w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/228_Nucleotides-01-300x223.png 300w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/228_Nucleotides-01-768x572.png 768w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/228_Nucleotides-01-65x48.png 65w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/228_Nucleotides-01-225x167.png 225w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/228_Nucleotides-01-350x260.png 350w, https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/228_Nucleotides-01.png 1114w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-1747\" class=\"wp-caption-text\"><strong>Figure 11. Nucleotides.<\/strong> (a) The building blocks of all nucleotides are one or more phosphate groups, a pentose sugar, and a nitrogen-containing base. (b) The nitrogen-containing bases of nucleotides. (c) The two pentose sugars of DNA and RNA.<\/figcaption><\/figure>\n<p style=\"text-align: justify\">In contrast, RNA consists of a single strand of sugar-phosphate backbone studded with bases. Messenger RNA (mRNA) is created during protein synthesis to carry the genetic instructions from the DNA to the cell\u2019s protein manufacturing plants in the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2131\">cytoplasm<\/a>, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_1267_2203\">ribosomes<\/a>.<\/p>\n<figure style=\"width: 804px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image13.png\" alt=\"image\" width=\"804\" height=\"1028\" \/><figcaption class=\"wp-caption-text\"><strong>Figure 12. DNA.<\/strong> In the DNA double helix, two strands attach via hydrogen bonds between the bases of the component nucleotides.<\/figcaption><\/figure>\n<figure style=\"width: 142px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-content\/uploads\/sites\/750\/2019\/07\/image14.png\" alt=\"image\" width=\"142\" height=\"142\" \/><figcaption class=\"wp-caption-text\">Watch <a href=\"https:\/\/youtu.be\/YO244P1e9QM\">this Amoeba Sisters video<\/a> to learn more about biomolecules! Direct link:\u00a0<a href=\"https:\/\/youtu.be\/YO244P1e9QM\">https:\/\/youtu.be\/YO244P1e9QM<\/a><\/figcaption><\/figure>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\"><a id=\"p\"><\/a>Review Questions<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p><strong>Part 1.<\/strong> <strong>Chemistry of carbon<\/strong><\/p>\n<div id=\"h5p-90\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-90\" class=\"h5p-iframe\" data-content-id=\"90\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"3-1\"><\/iframe><\/div>\n<\/div>\n<div id=\"h5p-91\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-91\" class=\"h5p-iframe\" data-content-id=\"91\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"3-2\"><\/iframe><\/div>\n<\/div>\n<p><strong>Part 2.<\/strong> <strong>Carbohydrates<\/strong><\/p>\n<div id=\"h5p-92\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-92\" class=\"h5p-iframe\" data-content-id=\"92\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"3-3\"><\/iframe><\/div>\n<\/div>\n<div id=\"h5p-93\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-93\" class=\"h5p-iframe\" data-content-id=\"93\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"3-4\"><\/iframe><\/div>\n<\/div>\n<p><strong>Part 3.<\/strong> <strong>Lipids<\/strong><\/p>\n<div id=\"h5p-94\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-94\" class=\"h5p-iframe\" data-content-id=\"94\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"3-5\"><\/iframe><\/div>\n<\/div>\n<div id=\"h5p-95\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-95\" class=\"h5p-iframe\" data-content-id=\"95\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"3-6\"><\/iframe><\/div>\n<\/div>\n<p><strong>Part 4.<\/strong> <strong>Proteins<\/strong><\/p>\n<div id=\"h5p-96\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-96\" class=\"h5p-iframe\" data-content-id=\"96\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"3-7\"><\/iframe><\/div>\n<\/div>\n<div id=\"h5p-97\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-97\" class=\"h5p-iframe\" data-content-id=\"97\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"3-8\"><\/iframe><\/div>\n<\/div>\n<p><strong>Part 5.<\/strong> <strong>Nucleotides and nucleic acids<\/strong><\/p>\n<div id=\"h5p-99\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-99\" class=\"h5p-iframe\" data-content-id=\"99\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"3-10\"><\/iframe><\/div>\n<\/div>\n<div id=\"h5p-100\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-100\" class=\"h5p-iframe\" data-content-id=\"100\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"3-11\"><\/iframe><\/div>\n<\/div>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<\/div>\n<div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_1267_2065\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2065\"><div tabindex=\"-1\"><p>A substance that contains both carbon and hydrogen.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2073\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2073\"><div tabindex=\"-1\"><p>A subatomic particle having a negative charge and nearly no mass; found orbiting the atom\u2019s nucleus.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2090\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2090\"><div tabindex=\"-1\"><p>Outermost electron shell of an atom.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2098\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2098\"><div tabindex=\"-1\"><p>Chemical bond in which two atoms share electrons, thereby completing their valence shells.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2145\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2145\"><div tabindex=\"-1\"><p>An organic compound consisting entirely of carbon and hydrogen.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2146\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2146\"><div tabindex=\"-1\"><p>Group of atoms linked by strong covalent bonds that tends to behave as a distinct unit in chemical reactions with other atoms.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2125\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2125\"><div tabindex=\"-1\"><p>A functional group, OH, present in many organic compounds including alcohols.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2147\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2147\"><div tabindex=\"-1\"><p>Chemical functional group consisting of COOH, an important part of organic acids.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2148\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2148\"><div tabindex=\"-1\"><p>Chemical functional group NH2, a component of amino acids.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2149\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2149\"><div tabindex=\"-1\"><p>A chemical function group, CH3, a component of fatty acids.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2150\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2150\"><div tabindex=\"-1\"><p>Chemical functional group, PO4-, a component of phospholipids and nucleic acids (including ATP).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2151\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2151\"><div tabindex=\"-1\"><p>large molecule formed by covalent bonding; classes of macromolecule discussed in this course include carbohydrates, lipids, proteins and nucleic acids.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2152\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2152\"><div tabindex=\"-1\"><p>A molecule that can react with other similar monomers to form a polymer; e.g. amino acids combine to form proteins.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2153\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2153\"><div tabindex=\"-1\"><p>A molecule formed of many monomers together forming a macromolecule.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2114\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2114\"><div tabindex=\"-1\"><p>Chemical reaction in which reactants combine to form a new compound, with one reactant gives up an atom of hydrogen and another reactant gives up a hydroxyl group (OH).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2115\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2115\"><div tabindex=\"-1\"><p>Chemical reaction in which a molecule water is split into H and OPH, thereby breaking a bond and severing a compound.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2154\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2154\"><div tabindex=\"-1\"><p>Class of organic compounds built from sugars, molecules containing carbon, hydrogen, and oxygen in a 1-2-1 ratio.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2100\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2100\"><div tabindex=\"-1\"><p>Molecule with regions that have opposite charges resulting from uneven numbers of electrons in the nuclei of the atoms participating in the covalent bond.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2155\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2155\"><div tabindex=\"-1\"><p>Five or six-carbon molecule that are monomers of carbohydrates; examples include glucose, fructose, galactose, ribose and deoxyribose.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2157\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2157\"><div tabindex=\"-1\"><p>A complex molecule formed of many (up to a thousand or more) monosaccharides; e.g. glycogen, starches, and cellulose.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2070\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2070\"><div tabindex=\"-1\"><p>Monosaccharide commonly used as energy in the body (substrate for glycolysis).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2156\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2156\"><div tabindex=\"-1\"><p>Molecule formed of a pair of monosaccharides; important to human physiology are sucrose, lactose and maltose.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2158\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2158\"><div tabindex=\"-1\"><p>Polysaccharide used as a storage form of glucose in the liver.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2159\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2159\"><div tabindex=\"-1\"><p>Coating of carbohydrate molecules that surrounds the cell membrane.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2074\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2074\"><div tabindex=\"-1\"><p>Nucleotide containing ribose and an adenine base that is essential in energy transfer.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2161\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2161\"><div tabindex=\"-1\"><p>Class of nonpolar organic compounds built from hydrocarbons and distinguished by the fact that they are not soluble in water.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2110\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2110\"><div tabindex=\"-1\"><p>In chemistry, a homogeneous liquid mixture in which a solute is dissolved into molecules within a solvent.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2162\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2162\"><div tabindex=\"-1\"><p>Combination of two or more unmixable liquids where one liquid contains a dispersion of the other liquids (often as tiny droplets).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2063\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2063\"><div tabindex=\"-1\"><p>A substance composed of two or more different elements joined by chemical bonds.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2163\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2163\"><div tabindex=\"-1\"><p>Molecule that forms the 'backbone' of many lipids, including triglycerides.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2164\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2164\"><div tabindex=\"-1\"><p>Consisting of a carboxyl group (COOH) and an unbranched hydrocarbon chain. A non-polar component of all lipids.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2165\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2165\"><div tabindex=\"-1\"><p>Organic compound required by the body to perform biochemical reactions like metabolism and bone, cell, and tissue growth.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2166\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2166\"><div tabindex=\"-1\"><p>An amphipathic lipid molecule containing a phosphate head (polar) and two fatty acid tails (non-polar). The major molecule comprising plasma membranes.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2099\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2099\"><div tabindex=\"-1\"><p>Opposite of polar; molecule with  electrons that are relatively equally shared in covalent bonds.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2177\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2177\"><div tabindex=\"-1\"><p>\"Water hating\"; a molecule or portion thereof that is nonpolar and therefore water insoluble.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2178\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2178\"><div tabindex=\"-1\"><p>\"Water loving\"; a molecule or portion thereof that is polar and therefore water soluble.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2168\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2168\"><div tabindex=\"-1\"><p>(Also, sterol) lipid compound composed of four hydrocarbon rings bonded to a variety of other atoms and molecules; not to be confused with anabolic steroids, a synthetic supplement<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2068\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2068\"><div tabindex=\"-1\"><p>The smallest unit of an element that retains the unique properties of that element.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2066\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2066\"><div tabindex=\"-1\"><p>Two or more atoms covalently bonded together.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2167\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2167\"><div tabindex=\"-1\"><p>Chemically, a type of steroid, cholesterol is a component of cell membranes and a precursor of some important vitamins and hormones.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2169\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2169\"><div tabindex=\"-1\"><p>Alkaline solution produced by the liver and important for the emulsification of lipids.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2170\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2170\"><div tabindex=\"-1\"><p>Process of forming an emulsion.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2171\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2171\"><div tabindex=\"-1\"><p>Secretion of an endocrine organ that travels via the bloodstream or lymphatics to induce a response in target cells or tissues in another part of the body.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2069\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2069\"><div tabindex=\"-1\"><p>Class of organic compounds that are composed of many amino acids linked together by peptide bonds.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2179\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2179\"><div tabindex=\"-1\"><p>Building block of proteins; characterized by an amino and carboxyl functional groups and a variable side-chain.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2180\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2180\"><div tabindex=\"-1\"><p>A type of covalent bond occurring between amino acids.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2174\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2174\"><div tabindex=\"-1\"><p>The most abundant of three protein fibres found in the extracellular matrix of connective tissues.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2173\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2173\"><div tabindex=\"-1\"><p>Molecule (usually a protein) that catalyzes chemical reactions.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2133\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2133\"><div tabindex=\"-1\"><p>(Also, immunoglobulin) antigen-specific protein secreted by plasma cells.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2172\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2172\"><div tabindex=\"-1\"><p>Chemical signal that is released from the synaptic end bulb of a neuron to cause a change in the target cell.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2181\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2181\"><div tabindex=\"-1\"><p>Excitable neural cell that transfer nerve impulses.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2185\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2185\"><div tabindex=\"-1\"><p>As a molecule, a short chain of amino acids. Also refers to something related to proteins.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2182\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2182\"><div tabindex=\"-1\"><p>(Also, somatotropin) anterior pituitary hormone that promotes tissue building and influences nutrient metabolism.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2183\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2183\"><div tabindex=\"-1\"><p>Organic compound, or portion of a molecule, composed entirely of hydrogen and carbon atoms.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2184\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2184\"><div tabindex=\"-1\"><p>An ionic solution with basic properties (pH &gt;7).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2186\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2186\"><div tabindex=\"-1\"><p>A chain of amino acids, typically fewer than 100.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2187\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2187\"><div tabindex=\"-1\"><p>Oxygen-carrying protein in erythrocytes (red blood cells).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2188\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2188\"><div tabindex=\"-1\"><p>Protein that makes up most of the thin myofilaments in a sarcomere muscle fibre.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2189\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2189\"><div tabindex=\"-1\"><p>Protein that makes up most of the thick cylindrical myofilament within a sarcomere muscle fibre.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2194\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2194\"><div tabindex=\"-1\"><p>Type of tissue that serves to hold in place, connect, and integrate the body\u2019s organs and systems.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2195\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2195\"><div tabindex=\"-1\"><p>One of three protein fibres found in connective tissues.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2190\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2190\"><div tabindex=\"-1\"><p>A chemical system that resists change in pH of a solution by either accepting or releasing hydrogen ions in response to acids or bases, respectively.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2192\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2192\"><div tabindex=\"-1\"><p>Hormone that enhances the cellular uptake and utilization of glucose, thereby decreasing blood glucose levels.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2191\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2191\"><div tabindex=\"-1\"><p>Hormone stored in the posterior pituitary gland and important in stimulating uterine contractions in labor, milk ejection during breastfeeding, and feelings of attachment (also produced in males).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2193\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2193\"><div tabindex=\"-1\"><p>An infectious agent that causes disease, typically a bacterium, virus, fungus, or microscopic parasite.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2196\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2196\"><div tabindex=\"-1\"><p>Class of organic compounds composed of one or more phosphate groups, a pentose sugar, and a base.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2197\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2197\"><div tabindex=\"-1\"><p>Stored energy matter possesses because of the positioning or structure of its components.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2199\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2199\"><div tabindex=\"-1\"><p>Reactions that build smaller molecules into larger molecules.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2075\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2075\"><div tabindex=\"-1\"><p>Lower energy form of ATP, containing two phosphate groups after the third phosphate group phosphorylated another molecule and transferring energy to it.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2198\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2198\"><div tabindex=\"-1\"><p>addition of one or more phosphate groups to an organic compound<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2200\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2200\"><div tabindex=\"-1\"><p>Deoxyribose-containing nucleic acid that stores genetic information.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2201\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2201\"><div tabindex=\"-1\"><p>Ribose-containing nucleic acid that helps manifest the genetic code as protein.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2103\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2103\"><div tabindex=\"-1\"><p>Dipole-dipole bond in which a hydrogen atom covalently bonded to an electronegative atom is weakly attracted to a second electronegative atom.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2202\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2202\"><div tabindex=\"-1\"><p>A long DNA molecule, combined with proteins that contains a number of genes. The normal chromosome compliment is 23 pairs of homologous chromosomes, one each from mother and father.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2131\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2131\"><div tabindex=\"-1\"><p>Internal material between the cell membrane and nucleus of a cell, mainly consisting of a water-based fluid called cytosol, within which are all the other organelles and cellular solute and suspended materials.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_1267_2203\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_1267_2203\"><div tabindex=\"-1\"><p>Cellular organelle that functions in protein synthesis.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":10,"menu_order":3,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1267","chapter","type-chapter","status-publish","hentry"],"part":19,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/pressbooks\/v2\/chapters\/1267","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/wp\/v2\/users\/10"}],"version-history":[{"count":25,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/pressbooks\/v2\/chapters\/1267\/revisions"}],"predecessor-version":[{"id":3240,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/pressbooks\/v2\/chapters\/1267\/revisions\/3240"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/pressbooks\/v2\/parts\/19"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/pressbooks\/v2\/chapters\/1267\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/wp\/v2\/media?parent=1267"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/pressbooks\/v2\/chapter-type?post=1267"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/wp\/v2\/contributor?post=1267"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/dcbiol110311092nded\/wp-json\/wp\/v2\/license?post=1267"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}