The ATP synthase protein uses a proton gradient across the cell membrane to drive ATP synthesis. Assume the protein acts as a proton channel and that the concentrations of protons are [H⁺]cytosol = 2 x 10⁻⁵ M and [H⁺]matrix = 5 x 10⁻⁶ M. What is the change in Gibbs free energy (ΔG) for the synthesis of one ATP molecule?
a) -30 kJ/mol
b) +30 kJ/mol
c) -60 kJ/mol
d) +60 kJ/mol