chap02outline - Chapter 2 - Chemical Basis of Life 2.1...

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Chapter 2 - Chemical Basis of Life 2.1 Introduction (p. 32) A. Chemistry deals with the composition of substances and how they change. B. A knowledge of chemistry is necessary for the understanding of physiology. C. Body functions depend on chemical changes within cells. 2.2 Structure of Matter (p. 32) A. Elements and Atoms; (p. 32; Table 2.1) 1. All matter is composed of elements, 92 of which occur naturally. 2. Living organisms require about 20 elements, of which oxygen, carbon, hydrogen, and nitrogen are most abundant. 3. Elements are composed of atoms; atoms of different elements vary in size and in how they interact. B. Atomic Structure (p. 32; Fig. 2.1; Table 2.2) 1. An atom consists of a nucleus containing protons and neutrons, with electrons in orbit around the nucleus. 2. Protons, with a positive charge, are about equal in size to neutrons, which have no charge. 3. Electrons are much smaller and bear a negative charge. 4. An electrically neutral atom has equal numbers of protons and electrons. 5. The number of protons denotes the atomic number of an element; the number of protons plus the number of neutrons equals the atomic weight. C. Bonding of Atoms (p. 33; Figs. 2.2-2.5) 1. Atoms form bonds by gaining, losing, or sharing electrons. 2. Electrons are found in shells around the nucleus. a. The first energy shell holds two electrons; the second and third energy shells each hold eight electrons. 3. Atoms with incompletely filled outer shells tend to be reactive to form stable outer shells. 4.
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This note was uploaded on 05/20/2010 for the course PHYSIOLOGY Physiology taught by Professor Holes during the Spring '10 term at Open Uni..

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chap02outline - Chapter 2 - Chemical Basis of Life 2.1...

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