Question

Subject: Cell Biology Why do some books state that the standard free energy for the hydrolysis of the gamma-phosphate group (the one furthest from the ribose) of ATP is different from the standard free energy change for the hydrolysis of the beta phosphate group (the middle phosphate group)? (my textbook shows the same standard free energy change for the hydrolysis of these two groups and that the textbook uses kcal/mol as the unit for free energy (some textbooks use kJ/mol)).

Answer 1

In an ATP, The two phosphoanhydride bond also called as the high energy bond are responsible for high energy content of the molecule. Hydrolysis of this bond provide energy that drives various biochemical reaction. Gamma phosphate is the primary phosphate group that is hydrolyzed when energy is neeeded to drive anabolic process. Since it is located farthest from the ribose sugar, it has higher energy of hydrolysis then the alpha or beta phosphate and hence their standard free energy for hydrolysis is different.