So the electron transport chain itself consists of a series of four protein complexes. We have protein complex one, two, three and four. And we also have a complex of proteins shown here that is known as ATP synthase that actually uses the electrochemical gradient to synthesize ATP molecules. So basically, protein complex one, protein complex three and four are used to establish the electrochemical gradient. And our ATP synthase uses that electrochemical gradient to synthesize our ATP molecule. So let's take a quick look at each one of these protein complexes and see what the function and the name of these protein complexes are.