MEDizzy - Given the following reaction: A + B C + D ΔGo′ =

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Energy Metabolism Overview

Given the following reaction: A + B C + D ΔGo′ = +15.5 kcal/mol And [A] = 5 mM, [B] = 4 mM, [C] = 0.5 mM, and [D] = 2.5 mM under cellular conditions, what is the overall Gibbs free energy change for the reaction at 25oC (R =1.98 × 10−3 kcal/mol/oK) (in kcal/mol)?

ExplanationRecall, ΔG = ΔGο′ + RTln ([C][D]/[A][B]), so for this reaction, ΔG = 15.5 + (1.98 ×10−3)(298) ln (1.25/20). Thus, ΔG = 15.5 + (0.59) ln (0.0625). ΔG = 15.5 – 1.64 = 13.86 kcal/mol. As ΔG is a positive number, under these conditions, the reaction is still an unfavorable reaction.