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. And this is known as the f kno region. And the f knot region actually contains that proton channel that rotates. And we'll talk about that much more detail in the next lecture.