9 kJ and 436 x 1 6 7 Of the dehydrogenase reactions in glycolysis and the TCA

9 kj and 436 x 1 6 7 of the dehydrogenase reactions

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7. Of the dehydrogenase reactions in glycolysis and the TCA cycle, all but one useNAD+as the electron acceptor. The lone exception is the succinate dehydrogenasereaction, which uses FAD, covalently bound to a flavoprotein, as the electronacceptor. The standard reduction potential for this bound FAD is in the range of0.003 to 0.091 V (Table 20.1). Compared to the other dehydrogenase reactions ofglycolysis and the TCA cycle, what is unique about succinate dehydrogenase? Whyis bound FAD a more suitable electron acceptor in this case? b. What is the equilibrium constant (Keq) for this reaction?c. Assume that (1) the actual free energy release accompanying the NADH-coenzyme Q reductase reaction is equal to the amount released under standardconditions (as calculated above), (2) this energy can be converted into thesynthesis of ATP with an efficiency = 0.75 (that is, 75% of the energy releasedupon NADH oxidation is captured in ATP synthesis), and (3) the oxidation of 1equivalent of NADH by coenzyme Q leads to the phosphorylation of 1 equivalent ofATP.Under these conditions, what is the maximum ratio of [ATP]/[ADP] attainable foroxidative phosphorylation when [Pi] = 1 mM? (Assume ∆Gº’ for ATP synthesis =+30.5 kJ/mol.) 60

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