So complex two, found on the inside portion of the inner membrane of the mitochondria, as shown here, contains the succinate dehydrogenase that is used by the citric acid cycle. And so actually, when we synthesize the fadh two in the citric acid cycle, it remains attached onto the succinate dehydrogenase of this protein complex two. And within that complex, that fadh two is actually oxidized back into fad. And that allows those two high energy electrons to be extracted by this complex. And as we'll see in the future lecture, those electrons are then taken by this coenzyme Q carrier, our Ubiquinone. And so Ubiquinone is able to shuttle to move the electrons not only from protein complex one to three, but also from protein complex two to three.