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Biology Test 2-11

Biology Test 2-11 - Biology Test 2 Circe Effect Odysseus...

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Biology Test 2 Circe Effect: Odysseus’ men Negatively charged substrate Circe Effect: Siren Song = Positively charged substrate Temperature Measure kinetic energy Heat Measure of total energy An enzyme-catalyzed reaction generally _______ its rate for a 10 degrees C temperature increase. Doubles An enzyme-catalyzed reaction generally doubles its rate for a 10 degrees C temperature increase. Regulation of enzyme activity How are enzymes controlled? Competitive Enzyme Inhibition Substrate and inhibitor compete for binding to the active site of the enzyme Inhibitor is structurally similar to the substrate Most apparent at low [substrate] Noncompetitive enzyme Inhibition (8.19) Inhibitor binds at a site away from the substrate binding site Causes a conformational change in the enzyme Allosteric Enzyme Regulation (8.20) “other site” Modulator (activator or inhibitor) binds to a site other than the substrate binding site active site
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Causes a conformational change of the enzyme which changes the activity Cooperativity Oxygen binding to hemoglobin 4 oxygen binding sites Binding alters the affinity for O2 Binding of the first O2 makes it more favorable for the next O2 to bind How do cells regulate their metabolic pathways? Metabolism – hallmarks Chemical transformations in small steps Each step catalyzed by a specific A>B>C>D>E A>B is catalyzed by enzyme 1 B>C is catalyzed by enzyme 2 Etc. How is a pathway turned off? Turn off the first enzymes Metabolism (8.21) A>B>C>DXE A>BXC>D>E AXB>C>D>E Allosteric Inhibition of the first step in the pathway Feedback Inhibition by the end product of the pathway The first enzyme of the pathway is allosterically regulated. Why not competitive inhibition? The pathway product of dissimilar for the substrate for the enzyme. Why allosteric Inhibiton? Typically an enzyme catalyzes a small change
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The product of a pathway may be very different from the starting material o Won’t be a good fit as a competitive inhibitor Therefore inhibit at an “other” site o Allosteric Inhibition RedOx Reaction (9.3) Reduction – Oxidation Reactions Biological RedOx reactions involve of electrons and hydrogens Biological redox reactions employ carrier molecules: coenzymes/cofectoors o Cycle between the reduced and oxidized forms o =”Reducing Power” Coenzymes/Cofactors NADP (oxidized form) NADPH (reduced form) FAD (oxidized form) FADH2 (reduced form) Another control problem Some processes require energy and “reducing power”
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