 That was a huge amount of fun information about membrane proteins. As always, we've created a number of study questions, and in this particular lecture we've deviated almost entirely from the book. Mostly because I love to share both our research, research from a bunch of close colleagues, and in general what's happening in the world, not least related to COVID and other stuff. The important point in this class is that we have three legs. We're standing with one leg solidly in physics, one leg in chemistry and structural biology, and one in life science. And I want you to keep all three in mind when you read through and study these questions. So for instance, if we're talking about conformational transitions or a process in an ion tunnel, what are the free energy components there? Say an ion moving through an ion tunnel. Where is the free energy lower? Where is it higher? Is there some sort of barrier in the middle that have to get over that is going to be the rate limiting step? There usually is. The sodium potassium ATPase. What free energies are high? What are low? Where do we add energy and where do we possibly get energy back? And I think you will be able to understand a surprising amount of biology from this.