Question

If the mitochondria have an excess of ATP built up then this energy can be used to regenerate

Select one:

a. complex organic molecules for the cell

b. NADH from NAD⁺

c. molecular oxygen from water    

d. A proton gradient

Answer 1

The answer is a. complex organic molecules for the cell

As the entered NADH undergoes oxidation and produced NAD+, this process prodcues ~3ATP, hence the option b. NADH from NAD⁺  is wrong.

During ETC at the last step, the water molecule will be formed with 2e electorns from the last electron carriers, 2 protons from the stroma and half oxygen. Hence the option c. molecular oxygen from water is wrong.

During ETC the proton gradient established passively hence the option d. A proton gradient also wrong.