<s>[INST] context: TCA / Krebs cycle Characteristics of TCA cycleuSite of occurrence - Mitochondria u20 ATPs are produced in one cycleuAmphibolic pathway (Anabolic + Catabolic pathway)uAnaplerotic reaction of TCA cycle - Pyruvate to Oxaloacetate by Pyruvate carboxylase Inhibitors Enzyme Inhibitor Aconitase Fluoroacetate Alpha ketoglutarate Arsenite Succinate dehydrogenase Malonate Irreversible reactions Reactions Enzyme Oxaloacetate - Citrate Citrate synthase Alpha ketoglutarate - Succinyl Co-AAlpha ketoglutarate dehydrogenase Oxidative / Substrate level phosphorylation Reactions Enzyme Succinyl Co-A - Succinate Succinate thiokinase Energetics 20 ATPVitamins in TCA cycle Riboflavin Niacin Thiamine Pantothenic acid FAD as cofactor NAD as cofactor Thiamine diphosphate as cofactor Coenzyme A as cofactor Alpha ketoglutarate dehydrogenase;Succinate dehydrogenase Isocitrate dehydrogenase;Alpha ketoglutarate dehydrogenase; Malate dehydrogenase Alpha ketoglutarate dehydrogenaseAcetyl CoA; Succinyl CoAHarper's illustrated Biochemistry , 30th ed , page 164 [/INST] question: Source of energy in Kreb cycle is | options: A: NAD B: NADP C: NADPH D: NADH | answer: D </s>