 So building membrane proteins from hydrophobic residues with only alpha helices is a very simple way to create them and that's why the first structures we found looked that way. Bacteria rhodopsin, 1990, seven transmembrane helices, all alpha helical and very hydrophobic. Aquaporin, 1997, well it's not quite helix, but you have two re-entrant helices and they pair up to effectively form one long helix. I will count that as one helix. That's fine, exception confirming the rule. But as time has gone on we've seen more and more proteins that are very complicated. Glutamate transporter, we have a horizontal helix here, multiple re-entrant regions, two proteins are likely interacting with each other, I won't even start to go into details. So why does this happen? Well likely because when we started determined structures we started with the lowest hanging fruit and the lowest hanging fruit were the ECWAS that were easy to predict and understand. Be aware that there is a selection bias in chemistry and in science in general. We start by finding the EC stuff. It doesn't mean that everything is EC. So are all membrane proteins helical? No, there are some beta sheets too, but in the interest of time I'm not really going to go through it. In terms of statistics 95% is helix to understand membrane protein interactions between lipids starting just with the helices is going to be fine enough for now.