102 handout 1018 KEY

102 handout 1018 KEY - Δ Δ Note the reduction of NAD can...

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For each of the following pairs of half-reactions, what the net reaction and the free energy change? Fumarate + 2H + + 2e - Succinate E’° = 0.03 V FAD + 2H + + 2e - FADH 2 E’° = - 0.22 V FADH 2 FAD + 2H + + 2e - E’° = 0.22 V Fumarate + FADH 2 FAD + succinate E’° = 0.25 V Δ Electrons flow from FADH 2 to fumarate. G’° = -nF E’° = -2 (96.5 kJ/V·mol) (0.25V) = -48.25 kJ/mol Δ Δ Note: the reason this reaction goes in reverse in the citric acid cycle is that the actual E’° of FAD when bound to the enzyme is much lower (~0.03 V), which makes the E’° and thus Δ the G’° for this reaction about zero. Therefore, it is readily reversible especially when Δ levels of succinate are high and/or levels of fumarate are low. Acetaldehyde + 2H + + 2e - Ethanol E’° = - 0.20 V N AD + + 2H + + 2e - NADH + H + E’° = - 0.32 V NADH + H + NAD + + 2H + + 2e - E’° = 0.32 V Acetaldehyde + NADH + H + Ethanol + NAD + E’° = 0.12 V Δ Electrons flow from NADH to acetaldehyde. G’° = -nF E’° = -2 (96.5 kJ/V·mol) (0.12V) = -23.16 kJ/mol
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Unformatted text preview: Δ Δ Note: the reduction of NAD + can also be written as NAD + + H + + 2e-NADH and has the same E’° as above (-0.32 V). If C-1 of ribulose 5-phosphate is labeled with 14 C, at which position(s) does the label appear in sedoheptulose 7-phosphate? Carbons 1 and 3 If C-2 of ribulose 5-phosphate is labeled with 14 C, at which position(s) does the label appear in erythrose 4-phosphate? Carbon 1 If C-3 of ribulose 5-phosphate is labeled with 14 C, at which position(s) does the label appear in sedoheptulose 7-phosphate? in GAP? Carbon 5 of sedoheptulose 7-phosphate and carbon 1 of GAP If C-4 of ribulose 5-phosphate is labeled with 14 C, at which position(s) does the label appear in erythrose 4-phosphate? in fructose 6-phosphate? Carbon 3 of erythrose 4-phosphate and carbon 5 of fructose 6-phosphate...
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This note was uploaded on 04/02/2008 for the course MCB 102 taught by Professor Staff during the Spring '08 term at Berkeley.

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