Well, Fadh two is not formed in glycolysis and it's not formed in pyruvate decarboxylation. It's only formed in the citric acid cycle. In fact, our Fadh two is formed directly in protein complex number two known as succinate oxidoreductase that is found on the electron transport chain. So we synthesize Fadh two inside protein complex number one and then we oxidize it back into Fad plus in the process releasing those electrons. As the electrons travel through protein complex three and four we once again pump our H plus ions in this case only two, in this case, four. And as we pump them, we create our electrochemical gradient that is used by ATP synthase to synthesize our ATP molecules.