Question

The standard-state free energy change in oxidizing NADH with oxygen is -220 kJ/mol (-52.6 kcal/mol). If we accept this value as representative of the actual free energy released (ΔG), which is not necessarily the case (see previous problem), then how many ATPs could potentially be synthesized per NADH oxidized if the cost of ATP synthesis was 11.4 kcal/mol? Report your answer to the nearest tenths.

Answer 1

The freee energy change for oxidation of one mole of NADH is -52.6 kcal.

The negative sign implies this free energy is usable and can be used for ATP synthesis.

Each mole of ATP requires a free energy of 11.4 kcal.

Hence, Number of moles of ATP that can be synthesized using the free energy of oxidation of one mole of NADH is

Hence, each molecule of NADH, when oxidized, produces enough free energy to synthesize 4.6 molecules of ATP.

note: Since, the free energy value reported here is not representative of the real value, the actual number of ATPs produced per molecule of NADH is actually around 3.