ACS Biochemistry Practice Exam

The conversion of succinate to fumarate occurs during Step 6 of the citric acid cycle (also known as the Krebs cycle). In this step, the enzyme succinate dehydrogenase catalyzes the oxidation of succinate to fumarate. This reaction involves the transfer of electrons to the electron transport chain via FAD, which is reduced to FADH2. The importance of this step lies in the fact that it is the only step in the citric acid cycle that directly involves the mitochondrial electron transport chain, facilitating the generation of ATP through oxidative phosphorylation. This step is essential for the continuation of the cycle, as it transforms succinate into a product that moves on to further reactions, ultimately leading to additional energy production for the cell.