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Published byDominic Carpenter Modified over 9 years ago
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1 SURVEY OF BIOCHEMISTRY Enzyme Catalysis
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2 General Properties of Enzymes High reaction rates –10 6 to 10 12 times faster than uncatalyzed reaction Mild reaction conditions –Temp < 100°C –Atmospheric Pressure –pH near 7 High reaction specificity Capacity for regulation
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3 Enzymes act on specific substrates Example of geometric specificity Phenylalanine Tyrosine L-DOPA (neurotransmitter)
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4 Classification of Enzymes
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5 Oxidoreductases Oxidoreductases catalyze redox reactions - those involving the transfer of electrons M M+M+ Oxidation Loss of e - X Reduction Gain of e - X-X-
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6 Oxidoreductases
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7 Transferases Transferases catalyze the transfer of a specific group from one molecule to another.
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8 Hydrolases Hydrolases break down chemicals through the use of water.
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9 Lyases Cleave C-C, C-O, C-N, and other bonds by elimination, leaving double bonds or rings
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10 Isomerases Catalyze geometric or structural changes within a molecule
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11 Ligases Catalyze the joining of 2 molecules coupled with the hydrolysis of ATP or some similar triphosphate.
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12 Enzyme bind substrates Binding of E to S usually involves noncovalent interactions Binding pocket is well- formed, but induced fitting can occur Substrate or inhibitor binding is usually based on complementarity
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13 Types of Cofactors Holoenzyme: protein + its cofactor Apoenzyme: protein without its cofactor Prosthetic group: tightly bound cofactor that does not dissociate from the enzyme
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14 Important Cofactors: NADH and NADPH Examples of cosubstrates
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15 Thermodynamics: Energy for Reaction Chemistry
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16 Thermodynamics: Energy for Reaction Chemistry
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17 PRS
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18 PRS A chemical reaction can occur spontaneously if ∆G is: 1.Positive 2.Negative 3.0 4.∆G does not relate to reaction spontaneity
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19 PRS Which best describes heme? 1.Oxidoreductase 2.Apoenzyme 3.Prosthetic group 4.Holoenzyme
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20 Reminders No office hours today - Mon, Jun 9 Exams to be returned on Wed Read Chapter 11 Practice drawing structures –All 20 amino acids –All 5 nucleotides (A, T, G, C, U) –NADH and NADPH
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