Aconitase catalyzes the citric acid cycle reaction: citrate isocitrate. The standard free energy change, ΔGo ', for this reaction is + 6.7 kJ/mol. However, the observed free energy change (ΔG) for this reaction in pig heart mitochondria is + 0.8 kJ/mol. What is the ratio of [isocitrate]/[citrate] in these mitochondria? If [isocitrate] = 0.03 mM, what is [citrate]

A. [isocitrate]/[citrate] = 0.724

B. [citrate] = 24.1 mM

Explanation:

Using the equation, ∆G'° = - RTlnK'eq

Where, ∆G'° = 0.8 KJ/mol = 800 J/mol; R is molar gas constant = 8.315 J/mol; T is standard temperature = 298 K; Keq is equilibrium constant = [isocitrate]/[citrate]

Making Keq subject of formula in the above equation;

Keq = e^ (-∆G'°/RT)

= e^ {-800 / (8.315*298) }

= e^ (-0.323)

Keq = 0.724

Therefore, [isocitrate]/[citrate] = 0.

724

B. Keq = [isocitrate]/[citrate]

Where Keq = 0.724, [isocitrate] = 0.03mM.

[citrate] = Keq/[isocitrate]

= 0.724/0.03

[citrate] = 24.1 mM