Energetics: Calculate the standard free energy of the reaction catalyzed by the

Question

Energetics:

Calculate the standard free energy of the reaction catalyzed by the alpha-ketoglutarate dehydrogenase complex from the standard reduction potentials listed in your book.

Apologies. The half reaction for KG is

succinyl-CoA + CO2 + H+ + 2e -ketoglutarate + CoA (E°’=-0.49V)

Using this value calculate the equilibrium constant for the reaction.

Under cellular conditions the concentrations of NAD+, NADH, alpha-ketoglutarate, succininyl-CoA, CoA, and CO2 are 0.3 mM, 0.015 mM, 0.256 mM, and 0.11 mM, 12 mM, and 3.78 mM respectively. What is the free energy of this reaction under these physiological conditions?

Explanation / Answer

succinyl-CoA + CO2 + H+ + 2e ---> ketoglutarate + CoA
-RTlnKeq = -nFE0 cell
8.314 * 300*ln(K) = 2 * -0.49 * 96500
K eq = 3.4143 * 10^-17
dG0 = -RTlnKeq
Keq = [ketoglutarate][CoA][NADH]/[succinyl-CoA][CO2][NAD+]
Keq = (0.256)*(12)*(0.015)/(0.11*3.78*0.3)
Keq = 0.3694
dG0 = -RTlnKeq
dG0 = -8.314 * 300 * ln (3.694 * 10^-4)
dGo = 19.713 kJ

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