{"id":3,"date":"2021-10-29T18:01:10","date_gmt":"2021-10-29T22:01:10","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/biology1190chemistry\/?p=3"},"modified":"2022-08-24T17:50:06","modified_gmt":"2022-08-24T21:50:06","slug":"main-body","status":"publish","type":"part","link":"https:\/\/pressbooks.bccampus.ca\/biology1190chemistry\/part\/main-body\/","title":{"raw":"Chapter 1: Atoms","rendered":"Chapter 1: Atoms"},"content":{"raw":"Matter<\/strong> is anything that has [pb_glossary id=\"27\"]mass[\/pb_glossary] and takes up space. All matter in the universe, including the human body, is made of [pb_glossary id=\"28\"]atoms[\/pb_glossary]<\/strong>.\r\n\r\nAtoms are composed of three subatomic particles: <\/strong>electrons, protons, and neutrons. Electrons<\/strong> are negatively charged and have negligible mass. Protons<\/strong> are positively-charged and neutrons <\/strong>have no charge but both protons and neutrons have measurable mass. The protons and neutrons reside in a dense central location called the atomic nucleus<\/strong> and the electrons surround the nucleus.\r\n\r\nThere are many models to describe atomic structure, including the Bohr model of the atom and the electron cloud model. The Bohr model<\/strong> proposes that electrons act like particles and surround the nucleus in discrete energy layers or electron shells <\/strong>(Figure 1). Every electron shell can accommodate a specific number of electrons or a specific amount of energy<\/strong>. This is because electrons move rapidly and, therefore, possess kinetic energy<\/strong> or the energy of movement. For example, the first shell is the energy shell closest to the nucleus. This shell can accommodate two electrons. The second and third shells can each accommodate a maximum of eight electrons. Some atoms have more than three electron shells but the atoms examined in this course will generally possess a maximum of three electron shells. <\/a>The farther an electron is from the nucleus, the more energy that electron has<\/em>. In other words, the outermost electron shell of an atom is the highest energy shell. Electrons fill the lowest energy or most stable shells first: the electron shells closest to the nucleus.\r\n\r\nThe electron cloud model proposes that electrons act like waves and their position can be described as a cloud around the nucleus. This course will not use the electron cloud model extensively but understanding the basic concept underlying this model will help you understand noncovalent interactions and more complex medical topics, such as medical imaging in your future studies.\r\n\r\nElectrons determine the important properties and behaviour of atoms, especially when interacting with other atoms.\r\n\r\n \r\n\r\n[caption id=\"attachment_408\" align=\"aligncenter\" width=\"620\"]\"Bohr Figure 1. Bohr model of a carbon atom. The atomic nucleus contains six (6) protons. Therefore, the atomic number of carbon is six (6).\u00a0 This carbon atom is uncharged. Therefore, the number of electrons is also six (6).<\/em>[\/caption]\r\n\r\nElements<\/strong> are matter composed of only one type of atom and elements differ by the number of subatomic particles. Elements are identified by a unique atomic number. <\/strong>The atomic number corresponds to the number of protons<\/em> in the nucleus. In an uncharged element, the number of protons (positive charges) is equal to the number of electrons (negative charges). The mass number <\/strong>of an element is the total number of protons and neutrons in the nucleus. The periodic table of elements<\/strong> organizes elements by increasing atomic number (left to right) and other atomic properties. For this course, you do not need to memorize the periodic table of elements.<\/strong>\r\n\r\n \r\n\r\n[caption id=\"attachment_413\" align=\"aligncenter\" width=\"620\"]\"Figure Figure 2. The periodic table of elements.<\/em>[\/caption]\r\n\r\nEvery organism has a unique set of essential elements<\/strong> or elements required for life. Humans require 25 essential elements<\/strong>; plants require 17 essential elements. Some essential elements are required in large amounts because they are common in our cells, such as carbon, hydrogen, oxygen, and nitrogen (Table 1). These are the major elements. <\/strong>Some essential elements are required in smaller quantities: the lesser elements<\/strong>. Some essential elements are required in minute quantities: the trace elements<\/strong>.\r\n

Table 1: Major, lesser, and trace elements of the human body.<\/strong><\/p>\r\n\r\n\r\n[caption id=\"attachment_417\" align=\"aligncenter\" width=\"620\"]\"Table1\" Source: Wikipedia. (https:\/\/en.wikipedia.org\/wiki\/Composition_of_the_human_body)<\/em>[\/caption]\r\n\r\nThough trace elements are required in tiny amounts, there are serious consequences to [pb_glossary id=\"53\"]deficiencies[\/pb_glossary]. <\/strong>For example, the recommended daily intake (RDI) of iodine is 150 micrograms (\u03bcg) for 19\u201330 year old adults who are not pregnant or breast-feeding. You can easily meet the RDI by using a small amount of iodized table salt on food or by consuming dairy or seafood.[footnote]source: Government of Canada: https:\/\/www.canada.ca\/en\/health-canada\/services\/food-nutrition\/healthy-eating\/dietary-reference-intakes\/tables\/reference-values-elements-dietary-reference-intakes-tables-2005.html<\/a>[\/footnote]. However, an iodine deficiency may result in an enlargement of the thyroid gland or goiter<\/strong>. The thyroid makes important hormones called T3 and T4 that contain many molecules of iodine in their structure. Without sufficient iodine, the thyroid enlarges to make more thyroid hormones to compensate for the low levels of T3 and T4.\r\n\r\n \r\n\r\n[caption id=\"attachment_419\" align=\"aligncenter\" width=\"620\"]\"Figure3\" Figure 3A. The thyroid gland is located at the base of the neck (above left). Enlargement of the thyroid gland is called a goiter (above right). Hyperthyroidism at the throat by Freelanceman is licenced by AdobeStock under CC BY 2.0<\/em>[\/caption]\r\n\r\n[caption id=\"attachment_422\" align=\"aligncenter\" width=\"620\"]\"Figure Figure 3B. The structure of thyroid hormone T3 contains iodine.<\/em>[\/caption]\r\n\r\nElements with the same atomic number but different mass numbers are called isotopes<\/strong>. These elements differ by the number of neutrons<\/em> in the nucleus and some isotopes are commonly used for medical imaging or treatments. For example, iodine has an atomic number of 53 and a mass number of 127. An isotope of iodine, iodine-131, possesses four<\/strong> additional neutrons and is used to treat thyroid cancer. <\/strong>\r\n\r\nIodine-131 is also radioactive<\/strong>, meaning the atom is unstable and can emit [pb_glossary id=\"59\"]radiation[\/pb_glossary]. Ionizing<\/strong> radiation<\/strong> is the emission of particles or waves that disrupt the structure of matter upon collision, resulting in damage to important cellular molecules such as DNA. For example, iodine-131 emits high energy electrons (beta emission) and a gamma ray. Gamma rays are high energy waves that can break double-stranded DNA and stop the cell from replicating or copying its DNA. This kills the cell.\r\n\r\n \r\n

\r\n

Chemistry in the clinic:<\/p>\r\n

Cancer is a complex disease but, for the purposes of Biology 1190, we can start by defining cancer as uncontrolled cell division. An individual with thyroid cancer<\/strong> suffers from uncontrolled cell division within the thyroid gland. To treat thyroid cancer, the patient is [pb_glossary id=\"121\"]infused[\/pb_glossary]<\/span> with iodine-131 in their blood. The blood carries the radioactive iodine-131 to the thyroid gland and the beta and gamma emissions of the radioactive isotope kill the cancerous thyroid cells. Some normal healthy cells may be killed or damaged by iodine-131 treatment. However, the damage may be repaired after treatment or that damage may be tolerated to kill the rapidly growing cancer. Iodine-131 is just one example of a medically useful radioactive isotope. Other radioactive isotopes are used to diagnose and to treat diseases and disorders.<\/p>\r\n\r\n<\/div>\r\n

Summary:<\/h2>\r\n