Question

Summarize why the difference between free energy change and standard free energy change depends on the concentrations of the reactants and products in biochemistry.

Answer 1

The Actual Free-Energy Change Depends on the Reactant and Product Concentrations. We must be careful to distinguish between two different quantities, the free-energy change, ΔG, and the standard free-energy change, ΔG°'. Each chemical reaction has a characteristic standard free-energy change, which may be positive, negative, or zero, depending on the equilibrium constant of the reaction. The standard free-energy change tells us in which direction and how far a given reaction will go to reach equilibrium when the initial concentration of each component is given.

ΔG° = -RT ln K_{eq and}   ΔG = ΔG° + RT ln K_eq where K is equilibrium constant and ΔG = Actual Free-Energy   ΔG° = standard free-energy change .

ΔG - ΔG° = RT ln K_eq

A + B C + D

K_eq = [C][D]/[A][B]

so the difference between free energy change and standard free energy change depends on K_eq . and  K_eq depends upon concentrations of reactions .

example in biochemistry

(1) Glucose + P_i glucose-6-phosphate + H₂O

K_{eq =} [glucose-6-phosphate] / [glucose][P_i]