Which reaction of the citric acid cycle proceeds by substrate level phosphorylation rather than through the electron transport chain?

• A Isocitrate to alpha ketoglutarate
• B Succinyl CoA to succinate ✓
• C Malate to oxaloacetate
• D Alpha ketoglutarate to succinyl CoA

Explanation

Succinyl CoA synthetase (succinate thiokinase) converts the high energy thioester bond of succinyl CoA directly into a phosphoanhydride bond of GTP, without involving the respiratory chain. The other three listed reactions generate NADH or FADH2, whose energy is captured later by oxidative phosphorylation. Other examples of substrate level phosphorylation are the phosphoglycerate kinase and pyruvate kinase steps of glycolysis.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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