 Bacteria rodopsin occurs in something called the purple membrane of bacteria and what makes it so special that technically it's a membrane, but there is so much protein in this membrane that I think 60% of something of the membrane weight is actually protein. So you might not see it perfectly, I'm going to show you better images of this later, but this is a trimer of the protein. Each protein unit here contains seven alpha helices and these alpha helices is just one long chain and they're going up and down through the membrane. So there are some loops that will be exposed on the outside, on the inside, while the parts that are going through the membrane is always alpha helico. The huge amount of protein in this membrane means that there is hardly any freely diffusing parts here. You can almost think of this as the lipids being packed between multiple copies of the proteins, which was, again, one of the reasons why it was easier to crystallize this protein. But this was a landmark result and it was the start of membrane protein structural biology. If you wonder why it's called the purple membrane, if you take that crystal and grind it up, it's going to look like that. So the high density of protein in this membrane, combined with the lipids, actually makes it scatter light in a way that it appears purple, fun side results. That might be a bit difficult to visualize. So if we take a model of this protein and put it in the lipid bilayer, again, now we've taken a lipid bilayer here in a computer. The lipid bilayer would not have been part of that structure, it would look something like this. So you can count the helices here, starting at the blue and then go into the red and there are one, two, three, four, five, six, seven of them. And today there are a ton of computer simulations of these. Let's have a look at that and magnify that, but I need to erase this first.