So high energy electron carriers called NADH molecules pass their electrons to flavin mononucleotide of complex number one which then shuttles those electrons via a series of iron sulfur groups and onto a molecule known as Ubiquinone. And the Ubiquitone in humans is known as coenzyme Q ten. Now, fadh two is itself synthesized in protein complex number two. 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.