Question

In which of the following reaction substrate-level phosphorylation occurs during respiration?

• A. Citric acid $\to \alpha$ -ketoglutaric acid
• B. Malic acid $\to$ oxaloacetic acid
• C. $\alpha$ -ketoglutaric acid $\to$ Succinyl-CoA
• D. Succinyl-CoA $\to$ Succinic acid

Answer 1

Answer: (D)

Substrate-level phosphorylation is the direct synthesis of ATP in the reaction mechanism, also known as transphosphorylation. In Kreb's cycle during conversion of succinyl CoA to succinic acid a molecule of GTP is synthesized. In a coupled reaction GTP is converted to GDP with the simultaneous synthesis of ATP from ADP.