chap04outline - Chapter 4 - Cellular Metabolism 4.1...

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Chapter 4 - Cellular Metabolism 4.1 Introduction (p. 74) A. A living cell is the site of enzyme-catalyzed metabolic reactions that maintain life. 4.2 Metabolic Processes (p. 74) A. Metabolic reactions are of two types: in anabolic reactions, larger molecules are constructed from smaller ones, a process requiring energy; in catabolic reactions, larger molecules are broken down, releasing energy. B. Anabolism (p. 74; Figs. 4.1-4.3) 1. Anabolism provides the substances needed for growth and repair. 2. These reactions occur by dehydration synthesis, removing a molecule of water to join two smaller molecules. 3. Polysaccharides, lipids, and proteins are constructed via dehydration synthesis. a. The bond between two amino acids is a peptide bond; two bound amino acids form a dipeptide, while many joined form a polypeptide. C. Catabolism (p. 74) 1. Catabolism breaks apart larger molecules into their building blocks. 2. These reactions occur by hydrolysis, wherein a molecule of water is inserted into a polymer and split into two smaller molecules. 3. The reactions of metabolism are often reversible. 4.3 Control of Metabolic Reactions (p. 75) A. Enzymes control the rates of all the metabolic reactions of the cell. B. Enzyme Action (p. 75; Fig. 4.4) 1. Enzymes are complex proteins that function to lower the activation energy of a reaction so it may proceed more rapidly. 2. Enzymes work in small quantities and are recycled by the cell. 3. Each enzyme is specific, acting on only one kind of substrate. 4. Active sites on the enzyme combine with the substrate and a reaction occurs. 5. The speed of enzymatic reactions depends on the number of enzyme and substrate molecules available. C. Factors That Alter Enzymes (p. 76) 1. Enzymes (proteins) can be denatured by heat, pH extremes, chemicals, electricity, radiation, and by other causes. 4.4
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chap04outline - Chapter 4 - Cellular Metabolism 4.1...

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