Final answer:
The TCA cycle reaction producing FADH₂ is catalyzed by succinate dehydrogenase in the conversion of succinate to fumarate, while a-ketoglutarate dehydrogenase complex produces NADH, not FADH₂.
Step-by-step explanation:
The TCA cycle reaction that produces FADH₂ is the one catalyzed by the enzyme succinate dehydrogenase. This enzyme facilitates the conversion of succinate to fumarate. The process involves a flavin-dependent dehydrogenation where FAD is covalently bound to the enzyme and is subsequently reduced to FADH₂. This reduced form is then utilized in the electron transport chain (ETC) where it is oxidized to produce ATP. Specifically, oxidizing one molecule of FADH₂ through the ETC leads to the production of 2 ATPs.
a-ketoglutarate dehydrogenase complex, on the other hand, is implicated in another reaction of the TCA cycle. It catalyzes the conversion of a-ketoglutarate to succinyl-CoA but does not generate FADH₂; instead, it produces NADH.