So as we discussed previously, in complex one of the electron transport chain, complex one essentially picks up the high energy electrons from NADH molecules and trams those electrons onto a special carrier molecule known as Ubiquinone. And when Ubiquinone grabs those electrons, it is reduced into Ubiquinol form that is given by QH two. So this molecule is known as Ubiquinol. Likewise, on complex two, the high energy electrons from Fadh two molecules are also transferred onto Ubiquinone to reduce Ubiquinone into Ubiquinol and the QH two, the Ubiquinone then travels onto complex three. And so in this lecture, I'd like to discuss the details of what happens when Ubiquinol, the reduced form of Ubiquinone, actually attaches onto complex three. Now, complex three goes by many names.