Let's actually discuss the mechanism of how ATP synthase carries out its function. So remember, the function of ATP synthase complex five is to actually use that proton motive force, the proton electrochemical gradient established by complexes one, three and four four to actually generate the high energy ATP molecules. And so what I'd like to focus on in this lecture and the next lecture is how the ATP synthase actually carries out its function, the mechanism of its function. Now in this lecture I'd like to focus on the catalytic subunit, the catalytic structure of ATP synthase. So remember in our previous discussion of the structure of ATP synthase we said that ATP synthase can actually be broken down into two regions. One of the regions is down in the actual inner membrane of the mitochondria in this region here.