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. So let's begin with protein complex number one. Now, protein complex number one consists of many proteins. And together, protein complex number one is known as Nadhq oxidoreductase or NADH dehydrogenase.