The primary medium for free energy storage in living cells is adenosine triphosphate (ATP). Its formation from adenosine diphosphate (ADP) is not spontaneous:

Cells couple ATP production with the metabolism of glucose ( a sugar): The reaction of 1 molecule of glucose leads to the formation of 38 molecules of ATP from ADP. Show how the coupling makes is reaction spontaneous. What fraction of the free energy released in the oxidation of glucose is stored in the ATP?

ADP- (aq) + HPO (aq) + H* (aq) ATP (aq) + HO(l) AG = +34.5 kJ C6H12O6 (aq) + 6 O2(g) 6 CO2(g) + 6 HO(l) AG= -2872 kJ