Chapter 3 - Chapter 3 Cell metabolism I. Metabolic...

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1 Chapter 3 Cell metabolism I. Metabolic reactions II. Factors that affect affect enzymes. III.Bioenergetics I. Metabolism A + B C + D Catabolic versus Anabolic – breaking down v. building up Hydrolysis versus Condensation – breaking v. forming bonds Phosphorylation versus Dephosphorylation – adding v. removing Pi Oxidation versus Reduction – removing v. adding electrons (H’s) Two important examples are: 1. NAD (oxidized) + 2 e - + H NADH (reduced) 2. FAD (oxidized) + 2 e - + 2 H FADH 2 (reduced) Metabolic Reactions continued • Reactions Involving An Energy Change ( E) a) Potential energy is released b) Potential energy is captured
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2 Reaction Activation Energy • Reactants must move into a transitional state before they can become products. • Energy must be added to the reactants to bring them into a transitional state [Activation Energy ] • Once a transition state is reached the reaction will occur spontaneously (downhill) • The greater the activation energy required the less likely the reaction will proceed. Metabolism and Activation Energy • The reactions of metabolism can proceed by themselves, but at a rate far too slow to support life. • Metabolism requires catalysts. Catalysts: A. increase the rate of chemical reactions. B. are not altered by the reaction. C. do not change the final result of a reaction. Enzymes A. The catalysts of metabolism are enzymes. B. Enzymes are proteins and therefore have specific 3-D shapes, that are by the genes. C. The reactants in an enzyme- catalyzed reaction fit into a specific pocket in the enzyme called the active site. D. Only an appropriately shaped substrate will fit into the active site.
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3 Enzymes Continued D. The enzyme-substrate complex orients the substrate molecules properly , so that new chemical bonds are more easily formed. E. Therefore, enzymes reduce the activation energy required for the reaction to proceed. F. By lowering the activation energy, enzymes allow a larger proportion of the total number of reactants to participate in the reaction, thus increasing the reaction rate. Isoenzymes Enzymes with the same function but different structure in different tissues CPK has 3 isoforms MM - skeletal muscle; BB - brain; MB - heart Can measure levels of MB in blood to detect heart disease (diagnostic value of isoenzymes) Substrate Concentration and Reversible Reactions Concentration dependent (Carbonic acid) Carbonic Anhydrase H 2 CO 3 H 2 O+ CO 2 In Tissues H 2 O + CO 2 H 2 CO 3 In Lungs H 2 CO 3 H 2 0 + CO 2 Law Of Mass Action
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4 II. Factors That Affect Enzymes At constant enzyme and substrate concentrations, the rate of metabolic reactions is affected by: 1) The reaction environment a) pH b) temperature 2) Structural regulators a) allosteric regulation b) covalent modification 1) pH • Each enzyme has optimal activity
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Chapter 3 - Chapter 3 Cell metabolism I. Metabolic...

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