What role does succinate dehydrogenase play in the Citric Acid Cycle?

Succinate dehydrogenase plays a crucial role in the Citric Acid Cycle by catalyzing the conversion of succinate to fumarate. This reaction is significant because it involves the oxidative dehydrogenation of succinate, where two hydrogen atoms are removed from the succinate molecule and transferred to the electron carrier FAD, reducing it to FADH2. This is the only step of the citric acid cycle that occurs in the inner mitochondrial membrane and is also linked to the electron transport chain. The production of FADH2 provides electrons used in cellular respiration to ultimately generate ATP, but succinate dehydrogenase itself does not produce ATP directly in this step.

The conversion of succinate to fumarate is essential for the continuation of the cycle, as it helps to maintain the flow of metabolites and supports the production of energy-rich molecules. It’s important to note that functions such as generating oxaloacetate, producing ATP directly from ADP, or converting isocitrate to alpha-ketoglutarate are attributed to different enzymes within the cycle and are not the role of succinate dehydrogenase. This specificity highlights the importance of each enzyme in the overall metabolism within the citric acid cycle.