Question

For the hydrolysis of ATP to ADP + ℗i, the free-energy change is -7.3 kcal/mol under standard conditions (1 M concentration of both reactants and products). In the cellular environment, however, the free-energy change is about -13 kcal/mol. What can we conclude about the free-energy change for the formation of ATP from ADP and ℗i under cellular conditions?

Answer 1

Ans : It is about +13 kcal/mol.

Reaction : The ΔG of a reaction is determined not only by the intrinsic properties of reactants and products, but also by their concentrations and other reaction conditions. The standard free-energy change (ΔG°) of a reaction is directly related to its equilibrium position because the actual ΔG is a function of both ΔG° and the concentrations of reactants and products. Since standard conditions in which the concentrations of all products and reactants are 1 M, The ΔG for the formation of ATP from ADP and ℗i under cellular conditions is the sum of the free-energy changes of its individual components.