Net generation of ATP in glycolysis-
Ans. is B i.e., 7 Energetics of Glvcoivsis o During glycolysis 2 ATP are utilized and 4 ATP are produced at substrate level. 2 reducing equalents NADH- are produced and reoxidized by electron transport 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 a net gain of 7 ATP molecules in aerobic glycolysisQ. o In anaerobic conditions, the reoxidation of NADH by electron transport 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 a net gain of 2 ATP molecules in anaerobic glycolysisQ. o 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 oniv 7ATPs during glvcoivsis. Reaction Enzyme No. of ATPs gained (new calculations) No. of ATPs gained (old calculations) Glucose - Glucose-6-phosphate Hexokinase, glucokinase -1 -1 Fructose-6-p -Fructose -1,6-bisphosphate Phosphofructokinase I -I -1 Glyceraldehyde-3-P - 1,3 bisphospboglycerate Glyceraldehyde-3 -P, dehydrogenase + 5 (2.5 x 2 NADH) +6 (3.0 x 2 NADH) 1,3 bisphosphoglycerate - 3-phosphogiycerate Phosphoglycerate mutase +2 +2 Phosphoenol pyruvate - Pyruvate Pyruvate kinase +2 +2 o Net generation in aerobic glycolysis 9-2 = 7 10-2 = 8
5
7
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