Which single step of the TCA cycle generates a high-energy phosphate bond by substrate-level phosphorylation?
- A Succinyl-CoA to succinate ✓
- B Isocitrate to alpha-ketoglutarate
- C Malate to oxaloacetate
- D Citrate to isocitrate
Correct answer: A. Succinyl-CoA to succinate
Explanation
Succinyl-CoA synthetase (succinate thiokinase) converts the thioester bond energy of succinyl-CoA into GTP via GDP phosphorylation, the only substrate-level phosphorylation within the cycle itself. The other listed steps are oxidative decarboxylation (producing NADH), dehydrogenation (producing NADH), and an isomerization respectively, none of which form a phosphoanhydride bond directly.
Reference: Lippincott Illustrated Reviews: Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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