And our fadh two transfers those electrons also to a molecule, our Ubiquinon. Now, once we reduce the Ubiquinon, once it gains those electrons, it becomes Ubiquinol, and it travels onto complex number three, where it transfers the electrons to yet another electron carrier that is water soluble, a small protein known as cytochrome C. Now, cytochrome C moves onto complex number four, where it transfers those electrons to complex number four. And these electrons are used to actually reduce oxygen and form water. Now, in the process, protein complex one, three, and four all release protons. They pump protons from the mitochondrial matrix into the intermembrane space, thereby establishing the electrochemical gradient. Notice that protein complex number two is not a proton pump.