bio 202 exam 1 study guide(9)

bio 202 exam 1 study guide(9) - 12 Enzymes catalyze...

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12. Enzymes: catalyze metabolic reactions that are crucial for life. The crystal structure of the enzyme biophosphoglyverate mutase are important to the function of human red blood cells. A. Enzymes are biological catalysts a. macromolecular-based catalysts that speed up biological reactions. (catalysts are substances that speed up reactions without themselves being consumed by the reactions). b. the active site is the pocket in an enzyme where it binds to substrates. c. enzyme-substrate complex: the combination of an enzyme with the substrate bound in its active site. B. the activation energy barrier a. every chemical reaction between molecules involves bond breaking and bond forming b. the initial energy needed to start a chemical reaction is called the free energy of activation, or activation energy (EA) c. activation energy is often supplied in the form of heat from the surroundings. d. substrates go through an intermediate transition state. After transition state is formed, products will form because they are more stable than the transition state. e. stability of the transition state will determine the activation energy. Activation energy is lowered by enzyme catalyzed reactions, as opposed to uncatalyzed reaction. C. Enzymes can lower activation energy by a. bringing substrates together in the proper orientation b. putting torque on the substrate. c. providing a proper chemical microenvironment d. adding or removing functional groups to or from the substrate. D. Enzymes as biological catalysts: mechanisms of enzyme catalysts
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a. substrate orientation: multiple substrates brought together in correct orientation to catalyze reaction. b. changing substrate reactivity: substrate influenced by amino acid chains at active site that alter chemical properties (e.g. charge) of substrate( changing substrate reactivity by altering its electrostatic configuration. c. inducing strain in the substrate: enzyme changes conformation of substrate to bring closer to conformation of transition state. (exerting physical stress on bonds in the substrate to be broken) the conformation of an enzyme will change during reactions but returns to original conformation once reaction is complete. a. induced fit: binding of substrate to enzyme induces further conformational changes in the enzyme that further improve the interaction between enzyme and substrate. E. Enzymes frequently require help from other substances Some enzymes require additional molecules for proper enzymatic activity a. cofactors: nonprotein enzyme helpers, usually metal ions, (minerals) found in the active site participating in catalysis (Zn, Mb, Mn destabilize bonds by drawing on electrons) b. coenzymes: nonprotein organic molecules required for proper enzymatic activity, vitamins B2(flavin), and B3(niacin), “store” energy containing electrons, vitamin B6 in amino acid metabolism and B12 in DNA, fatty acid metabolism.
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