Biochemistry 4th Edition by Reginald Garrett, Charles Grisham

Exercise 10

Determining the effects of NADH oxidation on oxidative phosphorylation
Consider the oxidation of NADH by molecular oxygen as carried out via the electron transport pathway
NADH + H+ + 1/2 O₂ NAD+ + H₂ O
a. What is the standard free energy change ( Gº'), for this reaction if E o'(NAD+/NADH+H+) = -0.320 V and E o' (1/2 O2/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 NADH 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 = 0.75 (that is, 75% of the energy released upon NADH oxidation is captured in ATP synthesis), and (3) the oxidation of 1 NADH leads to the phosphorylation of 3 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.)