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

Answer:

FAD substitution will produce 28 ATP instead of 36.

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