Complex II, otherwise termed Succinate-coenzyme Q reductase is an exotic member of the electron transport chain at least in 3 ways: unlike the other enzymes it is part of the TCA-Krebs-Szentgyörgyi cycle too due to its succinate dehydrogenase subunit , not any subunits of the complex are encoded by the mitochondrial DNA and it is not involved in proton pumping does not contain a proton pump that translocate protons from the matrix to the intermembrane space.
