The catalytic reaction within Complex II involves several steps: 1. Substrate Binding: Succinate binds to the active site on the SDHA subunit. 2. Oxidation Reaction: The SDHA subunit facilitates the oxidation of succinate to fumarate while reducing FAD to FADH2. 3. Electron Transfer: The electrons from FADH2 are transferred through iron-sulfur clusters in the SDHB subunit. 4. Reduction of Ubiquinone: Electrons are finally transferred to ubiquinone (coenzyme Q), reducing it to ubiquinol, which then enters the electron transport chain.
