Number of ATP molecules and NADH formed in each cycle of glycolysis ?

Ans. is 'a' i.e., 4 ATP, 2 NADH Enegetics of glvcolysis During glycolysis 2 ATP are utilized and 4 ATP are produced at substrate level. 2 reducing equalents NADH' are produced and reoxidized by electron transpo chain, to generata 5 ATP molecules (2.5 ATP per NADH' molecule). Thus total 9 ATP molecules are produced and 2 are utilized, i.e., There is net gain of 7 ATP molecules in aerobic glycolysis. In anaerobic conditions, the reoxidation of NADH by electron transpo chain is prevented and NADH gets reoxidized by conversion of pyruvate to lactate by lactate dehydrogenase. Thus, in anaerobic glycolysis only 4 ATP are produced at substrate level. Therefore, there is net gain of 2 ATP molecules in anaerobic glycolysis. Note : - Previous calculations were made assuming that NADH produces 3 ATPs and FADH2 generates 2 ATPs. This will amount to a net generation of 8ATPs per glucose molecule during glycolysis. Recent experiments show that these old values are overestimates and NADH produces 2.5 ATPs and FADH2 produces 1.5 ATPs. Thus, net generation is only 7ATPs during glycolysis.