Question

What role does the Krebs cycle play in the making of ATP?

Answer 1

Kreb cycle is also known as tricarboxylic acid cycle or citric acid cycle. In case of eukaryotes it occurs inside the mitochondrial matrix and in case of prokaryotes it occurs inside the cytosol. In the krebs cycle first there is condensation of oxaloacetate and acetyl coA. In this cyclic process GTP is generated by substrate level phosphorylation in step catalysed by enzyme succinate CoA synthetase. This GTP can donate terminal phosphate group to ADP to form ATP. This reaction is catalysed by enzyme known as nucleoside diphosphate kinase. Substrate level phosphorylation is that in which substrate has high phosphoryl transfer potential.

In the kreb cycle 3 NADH and 1 FADH​2 molecules are also produced per molecule of acetyl CoA. These reducing powers NADH and FADH​​​2 enter into electron transport chain for generation of more ATP molecules. 1 NADH molecule gives 2.5 ATP and 1 FADH​​2 give 1.5 ATP molecules. So kreb cycle in this way play importannt role in generating ATP through substrate level phosphorylation and also by producing reducing molecules like NADH and FADH​​​2 for producing ATP through electron transport chain.

Below is diagrammatic representation of kreb cycle

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