{"id":178,"date":"2022-03-05T18:32:55","date_gmt":"2022-03-05T23:32:55","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/biology1190chemistry\/?post_type=chapter&p=178"},"modified":"2022-04-28T19:31:03","modified_gmt":"2022-04-28T23:31:03","slug":"carbohydrates","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/biology1190chemistry\/chapter\/carbohydrates\/","title":{"raw":"Carbohydrates","rendered":"Carbohydrates"},"content":{"raw":"Carbohydrates<\/strong> are a biological polymer made of monomers called monosaccharides. <\/strong>Monosaccharides are sometimes referred to as \u201csimple sugars\u201d because they are the building block for large, complex carbohydrates or sugars. Monosaccharides containing six carbons, or hexose sugars<\/strong>, include glucose, fructose, and galactose. The hexose sugars are the main fuels of cells, especially glucose. Monosaccharides containing five carbons, or pentose sugars<\/strong>, include ribose and deoxyribose. The pentose sugars are important components of nucleic acids such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).\r\n\r\n \r\n\r\n[caption id=\"attachment_457\" align=\"aligncenter\" width=\"620\"]\"Figure Figure 15. Chemical structures of monosaccharides, including glucose, fructose, galactose, ribose, and deoxyribose.<\/em>[\/caption]\r\n\r\nCarbohydrates are named based on the length <\/strong>of the polymer chain. Monosaccharides are the simplest carbohydrate and contain carbon, hydrogen, and oxygen in a ratio of 1:2:1. When two monosaccharides are covalently linked by dehydration synthesis, a water molecule is generated, and the resulting disaccharide <\/strong>no longer contains a C:H:O ratio of 1:2:1.<\/em> The covalent bonds that link monosaccharides to one another and to other molecules is known as a glycosidic bond<\/strong>.\r\n\r\nThree biologically important disaccharides are sucrose, maltose, and lactose. Sucrose is a polymer containing one glucose and one fructose sugar. Maltose is a polymer containing two glucose sugars. Lactose is a polymer containing one glucose and one galactose sugar.\r\n\r\n \r\n\r\n \r\n\r\n[caption id=\"attachment_460\" align=\"aligncenter\" width=\"620\"]\"Figure Figure 16. Chemical structures of sucrose, maltose, and lactose.<\/em>[\/caption]\r\n\r\n[h5p id=\"73\"]\r\n\r\nSucrose is simple table sugar and sweetens food. Maltose also lends sweetness to foods and beverages, such as beer. Lactose is a sugar found in dairy products such as milk and cheese.\r\n\r\nCarbohydrates that consist of hundreds or thousands of monosaccharides are called polysaccharides<\/strong>. Polysaccharides play vital roles inside and outside of cells. Three biologically important polysaccharides include glycogen, starch, and cellulose. All three of the following polysaccharides consist only <\/em>of glucose monomers linked by glycosidic bonds. However, the arrangement <\/em>of glucose monomers differs between the polymers.\r\n\r\nGlycogen<\/strong> consists of branched chains of glucose monomers linked by glycosidic bonds. Glycogen is only made in animal cells, such as human liver cells or hepatocytes <\/strong>and is the storage polysaccharide <\/strong>of animal cells. When human cells need energy, cellular enzymes hydrolyze the glycosidic bond between a glucose monomer and the rest of the chain to release glucose for energy processing reactions.\r\n\r\nStarch<\/strong> is a long linear chain of glucose monomers linked by glycosidic bonds. The glycosidic bonds in starch and glycogen are identical but, unlike glycogen, starch is unbranched<\/strong>. Starch is synthesized by plant cells<\/strong> to store chemical potential energy. \u00a0Therefore, starch is known as the storage polysaccharide <\/strong>of plant cells. When humans eat plants, the starch in those cells can be broken down by our digestive system to release glucose to our cells for energy processing reactions.\r\n\r\nCellulose<\/strong>, like starch, is a long linear chain of glucose monomers linked by glycosidic bonds. However, the glycosidic bond in cellulose is different from the glycosidic bond in starch and glycogen. Cellulose forms rigid fibres<\/strong> that support the structure of plant cells in a structure known as the plant cell wall. <\/strong>As a result, cellulose is known as the structural polysaccharide of plant cells and cannot be made by human cells<\/em>. Human cells do not have the enzymes to hydrolyze the glycosidic bond in cellulose. Therefore, when we eat cellulose-rich plant foods, these materials travel nearly intact through our digestive systems and act as fibre to keep bowel movements regular.\r\n\r\n \r\n\r\n[caption id=\"attachment_491\" align=\"aligncenter\" width=\"620\"]\"Figure Figure 17. Chemical structures of starch, cellulose, glycogen.<\/em>[\/caption]\r\n\r\n[h5p id=\"74\"]\r\n\r\n[h5p id=\"75\"]\r\n\r\n ","rendered":"

Carbohydrates<\/strong> are a biological polymer made of monomers called monosaccharides. <\/strong>Monosaccharides are sometimes referred to as \u201csimple sugars\u201d because they are the building block for large, complex carbohydrates or sugars. Monosaccharides containing six carbons, or hexose sugars<\/strong>, include glucose, fructose, and galactose. The hexose sugars are the main fuels of cells, especially glucose. Monosaccharides containing five carbons, or pentose sugars<\/strong>, include ribose and deoxyribose. The pentose sugars are important components of nucleic acids such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).<\/p>\n

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Figure 15. Chemical structures of monosaccharides, including glucose, fructose, galactose, ribose, and deoxyribose.<\/em><\/figcaption><\/figure>\n

Carbohydrates are named based on the length <\/strong>of the polymer chain. Monosaccharides are the simplest carbohydrate and contain carbon, hydrogen, and oxygen in a ratio of 1:2:1. When two monosaccharides are covalently linked by dehydration synthesis, a water molecule is generated, and the resulting disaccharide <\/strong>no longer contains a C:H:O ratio of 1:2:1.<\/em> The covalent bonds that link monosaccharides to one another and to other molecules is known as a glycosidic bond<\/strong>.<\/p>\n

Three biologically important disaccharides are sucrose, maltose, and lactose. Sucrose is a polymer containing one glucose and one fructose sugar. Maltose is a polymer containing two glucose sugars. Lactose is a polymer containing one glucose and one galactose sugar.<\/p>\n

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\"Figure
Figure 16. Chemical structures of sucrose, maltose, and lactose.<\/em><\/figcaption><\/figure>\n
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