So complex one is a very massive complex. Now, complex one is also known as NADH dehydrogenase or NADH oxidoreductase. And the reason we call it this is because this is the complex of the electron transport chain that ultimately accepts the high energy electrons from NADH molecules that we generate in processes such as the citric acid cycle and glycolysis. So this L shape structure contains the horizontal component that lies in the membrane of the mitochondria, the inner membrane. And we have a vertical component that extends into the matrix of the mitochondria, and the NADH actually binds onto this extension that lies in the matrix of the mitochondria. And along with the NADH, an H plus iron is also actually used.