Question

Suppose NAD is unavailable because NADH cannot be oxidized due to a mutation in the NADH dehydrogenase (Complex I). If FAD could substitute for all NAD , how would this affect the total ATP produced by the complete oxidation of glucose

Answer 1

FAD substitution will produce 28 ATP instead of 36.

Step-by-step explanation:

NAD and FAD are coenzymes involved in reversible oxidation and reduction reactions. These compounds are also known as electron carriers. However NADH produce 3 electrons in electron transport chain and FADH2 produce 2 electron beacuase it transfer the electrons to second complex in ETC.

Normal prduction of ATP from glucose;

2 cytoplasmic NADH formed in glycolysis Each yields 2 ATP +4

2 NADH formed in the oxidation of pyruvate Each yields 3 ATP +6

2 FADH2 formed in the citric acid cycle Each yields 2 ATP +4

6 NADH formed in the citric acid cycle Each yields 3 ATP +18

2 ATP from glycolysis +2

2 ATP from citric acid cycle +2

Net yield ATP +36

C6H12O6 + 6 CO2 + 36 ADP + 36 Pi ⇒6 CO2 + 6 H2O + 36 ATP

If we replace the NAD with FAD the total ATP production would be.

2 cytoplasmic FADH2 formed in glycolysis Each yields 2 ATP +4

2 FADH2 formed in the oxidation of pyruvate Each yields 3 ATP +4

2 FADH2 formed in the citric acid cycle Each yields 2 ATP +4

6 FADH2 formed in the citric acid cycle Each yields 2 ATP +12

2 ATP from glycolysis

+2

2 ATP from citric acid cycle +2

Net yield ATP +28

C6H12O6 + 6 CO2 + 28ADP + 28 Pi ⇒6 CO2 + 6 H2O + 28 ATP