Biochemistry 4th Edition by Reginald Garrett, Charles Grisham

Exercise 9

Determining the impact of the succinate dehydrogenase reaction on oxidative phosphorylation
Consider the oxidation of succinate by molecular oxygen as carried out via the electron transport pathway.
succinate + 1/2 0 2 fumarate + H₂ O
a. What is the standard free energy change ( Gº'), for this reaction if E o'(fumarate/succinate) = +0.031 V and E o' (1/2O2/H2O) = +0.816 V.
b. What is the equilibrium constant (K eq ) for this reaction
c. Assume that (1) the actual free energy release accompanying succinate oxidation by the electron transport pathway is equal to the amount released under standard conditions (as calculated above), (2) this energy can be converted into the synthesis of ATP with an efficiency = 0.70 (that is, 70% of the energy released upon succinate oxidation is captured in ATP synthesis), and (3) the oxidation of 1 succinate leads to the phosphorylation of 2 equivalents of ATP. Under these conditions, what is the maximum ratio of [ATP]/[ADP] attainable for oxidative phosphorylation when [Pi] = 1 mM (Assume Gº' for ATP synthesis = +30.5 kJ/mol.)