Question

What are the assumptions made during the calculation of net gain of ATP in respiration?

Answer 1

During the glycolysis, 2ATPs are consumed in the pathway while 4 ATPs are released. Hence the net gain is of 2ATPs. Also, 2 molecules of NADH are produced from 2NADs. And one molecule of NADH= 3 ATPs. So net ATP gained is 5 and this pathway are run twice as to produce 2 molecules of pyruvate from a single glucose molecule, so the total ATPs gained 5*2= 10 ATPs.

During the link reaction, a single molecule of NADH is released from one pyruvate when it undergoes oxidative decarboxylation to acetyl CoA. So two molecules of pyruvate will form 2NADH i.e. = 2*3 = 6ATPS.

During the Krebs cycle, 3 NADH are produced i.e., 3*3 = 9 ATPs and 2 $FAD{H}_2$ are produced from a single molecule of acetyl Co-A and one mol. of FADH2= 2 ATPs. But we have 2 mol. of Acetyl CoA. So total ATP gained 11*2=22 ATPS.

So total gain of ATP during complete respiration is 38.