2011Exam2KEY

# Regulation of glycogen degradation proceeds normally

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Unformatted text preview: rine, and glucagon. Regulation of glycogen degradation proceeds normally, but these molecules can no longer regulate glycogen synthesis because glycogen synthase is always on. So there is no reciprocal regulation. 12. (20 points) Suppose you have isolated a new bacterium with unique components in its electron transfer chain, Q* (a modified quinone) and X. ————————————————————————————————————— Species Electrons transferred E'° (V) ————————————————————————————————————— Q* 2 +0.10 3+ X 1 +0.50 NADH 2 -0.32 ————————————————————————————————————— a) Assuming oxygen is the final electron acceptor, use the reduction potentials to deduce the complete electron transfer pathway involving these components, and NADH (4 components total: A → B → C → D). NADH → Q* → X3+ → Ο 2 b) What is the total ∆E'° for electron transfer through this pathway to oxygen? ∆E'° = E'°(oxidant) – E'°(reductant) = +0.82 – (–0.32) = +1.14 V c) Calculate the total ∆G'° per pair of electrons transferred through this pathway to oxygen. ∆G'° = –nℑ∆E'° = (–2)(96.48 kJ/V·mol)(1.14 V) = –220 kJ/mol d) Calculate the energy required to pump one proton across the membrane, if under typical conditions this bacterium has a membrane potential of 0.15 V and ∆pH = 0.2 (both terms should be unfavorable). T = 25˚C. For transfer of one proton. ∆Gtransport = ℑ∆V - 2.303RT ∆pH ∆Gtransport = (96.48 x 103 J/V·mol)(0.15V) -2.303(8.315J/K mol)(298K)(-0.2) ∆Gtransport = 14472 J/mol + 1141 J/mol = 15.6 kJ/mol e) Calculate the maximum number of protons that could theoretically be translocated across the membrane under standard conditions, per pair of electrons transferred through this chain of carriers. Assume standard state conditions. Number of protons = energy available/energy per proton = 220 kJ/mol / 15.6 kJ/mol per proton = 14.1 protons A maximum of 14 protons could be translocated per pair of electrons. 3...
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## This note was uploaded on 08/24/2013 for the course CHEM 423 taught by Professor Thompson during the Spring '11 term at UMass (Amherst).

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