Bi100 hapter 2 hemical Basis of Life Introduction: A. hemistry deals with the composition of matter and how it changes. B. A knowledge of chemistry is necessary for the understanding of physiology because of the importance of chemicals in body processes. Structure of Matter: A. Elements and Atoms: 1. Matter is anything that has weight and takes up space. 2. All matter is composed of elements. Yeah, I m made of elements. B 1
Structure of Matter: 3. Living organisms require about 20 elements, of which oxygen, carbon, hydrogen, and nitrogen are most abundant. 4. Elements are composed of atoms; atoms of different elements vary in size, weight, and interaction with other atoms. 5. Attractions between two or more atoms are called chemical bonds. Atomic Structure: 1. An atom consists of a nucleus containing protons and neutrons, with electrons in orbit around the nucleus in shells. 2. Protons, with a positive charge, are about equal in size to neutrons, which have no charge. Atomic Structure: 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. 6. Atoms with the same atomic number, but different numbers of neutrons are isotopes of an element. 2
Bonding of Atoms: 1. Atoms form bonds by gaining, losing, or sharing electrons. 2. Electrons are found in shells around the nucleus. 0 0 0 0 0 0 ydrogen () elium (e) Lithium (Li) Fig02.02 Atomic Structure 3. When atoms gain or lose electrons, they become ions with a charge. Whether they gain or lose will depend on how many electrons they have in the outer shell to start with. 4. ppositelycharged ions attract each other and form an ionic bond. Atomic Structure: 5. ovalent bonds are formed when atoms share electrons 6. A polar molecule has a covalent bond in which the electrons are not shared equally. 3
Molecules and ompounds: 1. A molecule is formed when two or more atoms combine. 2. If atoms of different elements combine, the molecule can also be called a compound. Formulas: 1. A molecular formula represents the numbers and types of atoms in a molecule. Ex: Glucose = 6 12 6 2. Various representations, called structural formulas, can be used to illustrate molecules. hemical eactions: 1. A chemical reaction occurs as bonds are formed or broken between atoms, ions, or molecules. 2. Those changed by the reaction are the reactants; those formed are the products. 3. Two or more atoms or molecules can be joined during synthesis. 4. Larger molecules can be broken into smaller ones in decomposition reactions. 4
Acids and Bases: 1. Substances that release ions in water are called electrolytes. 2. Electrolytes that release hydrogen ions () in water are called acids. 3. Electrolytes that release hydroxide () ions are called bases. Acids and Bases: 4. The concentrations of and in the body is very important to physiology. 5. p represents the concentration of hydrogen ions [ ] in solution. opyright The McGrawill ompanies, Inc. Permission required for reproduction or display. elative! Acidic! 8.4! amounts!! 6.6! 7.4! sodium! of (red)! cowʼs! human! bicarbonate! 5.3! and 4.2! milk! blood! cabbage! 11.5! (blue)! 3.0! tomato! 10.5! 2.0! household! apple! juice! milk of! gastric! ammonia! juice! 8.0! magnesia! juice! 7.0! egg! 6.0! distilled! white! corn! water! Basic!! p 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Acidic concentration increases! eutral concentration increases! Basic (alkaline) Fig02.11 Acids and Bases: A p of 7 indicates a neutral solution with equal numbers of hydrogen ions and hydroxyl () ions. a. a solution with a p of 07 is acidic and has more ions than b. a solution with a p of 714 is basic and has more ions than. *note that the p scale is an exponential scale (that means small changes in p represent large numbers in concentration) 5
Acids and Bases: 7. Buffers are chemicals that combine with excess acids or bases to help minimize p changes in body fluids. hemical onstituents of ells: A. rganic compounds contain both hydrogen and carbon. B. All other compounds are considered inorganic and they usually dissolve in water and release ions, making them electrolytes. Water: the most abundant compound in living things and makes up twothirds of the weight of adults. rganic Substances: arbohydrates arbohydrates provide energy for cellular activities and are composed of carbon, hydrogen, and oxygen. arbohydrates are made from monosaccharides (single sugars); disaccharides are two monosaccharides joined together; polysaccharides, such as starch, are built of many sugars. 6
rganic Substances: Lipids: Lipids are organic substances that are insoluble in water and include fats, phospholipids, and steroids. rganic Substances: Proteins: Proteins have a great variety of functions in the body as structural materials, as energy sources, as certain hormones, as receptors on cell membranes, as antibodies, and as enzymes to facilitate (or catalyze) metabolic reactions. rganic Substances Proteins contain,,, and atoms; some also contain S. Building blocks of proteins are the amino acids 7
rganic Substances opyright The McGrawill ompanies, Inc. Permission required for reproduction or display. Amino acids Proteins have complex shapes or conformations: primary structure (a) Primary structure Each! oblong shape in this! polypeptide chain represents! an amino acid molecule. The! whole chain represents a! portion of a protein molecule.! order of amino acids pleats or helices complex 3D folding 1o Pleated! structure! secondary structure tertiary structure (b) Secondary structure The! polypeptide chain of a protein! molecule is often either pleated! or twisted to form a coil. Dotted! lines represent hydrogen bonds.! groups (see fig. 2.17)! are indicated in bold.! oiled! structure! (c) Tertiary structure! The pleated and coiled! polypeptide chain of a! protein molecule folds! into a unique three! dimensional structure.! Threedimensional! folding! 2o 3o quaternary structure multiple proteins interacting (d) Quaternary structure Two or more! polypeptide chains may be connected! to form a single protein molecule. 4o rganic Substances: ucleic Acids: a. ucleic acids form DA and A. b. ucleic acids are of two major types: DA (with deoxyribose) and A (with ribose). c. A (ribonucleic acid) functions in protein synthesis; DA (deoxyribonucleic acid) stores the molecular code in genes. 8