During which process is GTP converted into ATP?

The conversion of GTP into ATP occurs during substrate-level phosphorylation. This process involves the direct transfer of a phosphate group to ADP from a high-energy substrate, such as GTP, resulting in the synthesis of ATP. In the context of the Citric Acid Cycle, one of the key steps involves the conversion of succinyl-CoA to succinate, in which a high-energy thioester bond is broken, releasing energy that is used to convert GDP (guanosine diphosphate) into GTP, and subsequently, GTP can be used to generate ATP directly.

This mechanism contrasts with oxidative phosphorylation, which relies on the electron transport chain and chemiosmotic coupling to generate ATP, as well as glycolysis, which primarily produces ATP and NADH through substrate-level phosphorylation and does not directly involve the conversion of GTP. The cycling of the TCA cycle refers to the entire sequence of reactions and does not specifically focus on the direct conversion of GTP to ATP, making substrate-level phosphorylation the most accurate choice for this particular process.