Question

The redox reactions in mitochondrial membrane can be summarized in the overall reaction scheme shown below:

Given the following information, calculate the theoretical maximum number of ATP molecules that can be synthesized when one molecule of NADH is oxidized:

½ O2 + 2H+ + 2e ↔ H2O (Eo = 0.82 V)

NAD+ + H+ + 2e ↔ NADH (Eo = -0.32 V)

ATP ↔ ADP + Pi (Go’= -30.5 kJ/mol)
a. 1
b. 2
c. 4
d. 7
e. 9

Answer 1

To calculate the maximum number of ATP molecules synthesized from one molecule of NADH, we use the total energy released during the oxidation of NADH and divide it by the energy required for ATP synthesis. This results in a theoretical maximum of roughly 7.15 ATP molecules, which is then rounded down to 7 ATP molecules per NADH oxidized.

Step-by-step explanation:

To calculate the theoretical maximum number of ATP molecules that can be synthesized when one molecule of NADH is oxidized, we must consider the potential energy difference created by the redox reactions in the mitochondrial membrane and how that corresponds to ATP production. The overall potential difference between the NADH/NAD+ couple and the O2/H2O couple is 1.14 V, which equates to -218 kJ/mol. The energy needed to synthesize one ATP molecule is -30.5 kJ/mol.

By dividing the total energy released by the oxidation of one molecule of NADH (-218 kJ/mol) by the energy required to synthesize one molecule of ATP (-30.5 kJ/mol), we can identify the number of ATP molecules that can be theoretically generated:

-218 kJ/mol ÷ -30.5 kJ/mol = 7.15

Since the number of ATP molecules synthesized must be a whole number, the theoretical maximum is rounded down to 7.