In the tricarboxylic acid cycle, a 6-carbon compound undergoes two successive steps of decarboxylation, leading to the formation of a 4-carbon intermediate. Which of the following specific events occurs during the immediate next step, when this newly formed 4-carbon intermediate is converted into the subsequent intermediate?

Step-by-step solution

In the TCA cycle, the 6-carbon compound isocitrate undergoes a decarboxylation to form the 5-carbon -ketoglutaric acid, which undergoes a second decarboxylation to form the 4-carbon intermediate succinyl-CoA. The immediate next step is the conversion of succinyl-CoA to succinic acid. During this conversion, a molecule of GTP is synthesised. This process is known as substrate-level phosphorylation. Reduction of FAD occurs in the subsequent step (succinic acid to fumaric acid), and oxidative phosphorylation occurs la