So we have protein complex one, protein complex two, protein complex three and four, as well as other proteins, as we'll see in a future lecture. And we have this final protein molecule known as ATP synthase. So ultimately, what happens is protein complex one is responsible for accepting those high energy electrons from NADH molecules produced in glycolysis and the citric acid cycle. And we extract these high energy electrons into this area here. At the same time, we also regenerate those NAD plus molecules needed for glycolysis and the citric acid cycle to actually continue taking place. Now, the Fadh two molecules produced in the citric acid cycle are actually taken by protein complex two.