And those two electrons then travel through a series of these iron sulfur clusters and ultimately end up being bound onto that coenzyme cue the Ubiquinone. When the Ubiquinone uptakes those two H ions, it then forms Ubiquinol, which detaches and moves on to complex three, as we'll see in the next lecture. And again, a very important distinction between complex one and complex two is the fact that complex one actually pumps those protons and helps generate that electrochemical gradient for hydrogen ions. But this one doesn't actually pump any protons. And that's precisely why, as we'll see in a future lecture, NADH is able to actually form a greater number of ATP molecules compared to the Fadh two. So the complex oxidizes succinate into fumarate, in the process forming the Fadh two, which is then oxidized back into Fad, and that release the two electrons, which ultimately move through these FES clusters and onto Ubiquinone to then form Ubiquinol.