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co03 - CHAPTER 3 THE CHEMISTRY OF ORGANIC MOLECULES Chapter...

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C HAPTER 3 T HE C HEMISTRY OF O RGANIC M OLECULES Chapter Outline 3.1 Organic Molecules A. Definitions 1. Organic molecules have carbon bonded to other atoms and determine structure and function of living things. 2. Inorganic molecules do not contain carbon and hydrogen together; inorganic molecules such as salt ions can play important roles in living things. B. The Carbon Atom 1. Most common elements in living things are carbon, hydrogen, nitrogen, and oxygen. 2. These four elements constitute about 95% of your body weight. 3. Chemistry of carbon allows the formation of an enormous variety of organic molecules. 4. Carbon has four electrons in outer shell; bonds with up to four other atoms (usually H, O, N, or another C). C. The Carbon Skeleton and Functional Groups 1. Ability of carbon to bond to itself makes possible carbon chains and rings; these structures serve as the backbones of organic molecules. 2. Functional groups are clusters of atoms with characteristic structure and functions. a. Addition of an –OH (hydroxyl group) turns a carbon skeleton into an alcohol. b. The ethanol alcohol is hydrophilic, it dissolves in water, because the –OH functional group is polar. c. Nonpolar molecules are repelled by water and do not dissolve in water; are hydrophobic. d. A hydrocarbon is hydrophobic except when it has an attached ionized functional group such as carboxyl (acid) (— COOH); then the molecule is hydrophilic. e. Carboxyl groups ionize in solution and release hydrogen ions, being both polar and acidic. f. Cells are 70–90% water; the degree organic molecules interact with water affects their function. 3. Isomers are molecules with identical molecular formulas but differ in arrangement of their atoms (e.g., glyceraldehyde and dihydroxyacetone). D. The Macromolecules of Cells 1. Cells contain four classes of macromolecules (carbohydrates, lipids, proteins, and nucleic acids) and they provide great diversity. 2. The largest macromolecules are polymers constructed of small subunits (e.g., monosaccharides, glycerol and fatty acids, amino acids, and nucleotides) that serve as monomers , subunits of polymers. 3. Polymers are the large macromolecules composed of three to millions of monomer subunits. 4. Polymers build by different bonding of different monomers; mechanism of joining and breaking these bonds is dehydration synthesis and hydrolysis. 5. Cellular enzymes carry out condensation synthesis and hydrolysis of polymers. 6. During dehydration synthesis , a water is removed and a bond is made (synthesis). a. When two monomers join, a hydroxyl (— OH) group is removed from one monomer and a hydrogen (— H) is removed from the other. b. This produces water. 7. Hydrolysis reactions break down polymers in reverse of dehydration; a hydroxyl (— OH) group from water attaches to one monomer and hydrogen (— H) attaches to the other.
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