So due to relatively weak intermolecular bonds, lipids and most proteins are in a constant state of lateral motion. The reason I say most proteins is because some of these proteins are actually attached to other things and so they don't actually move. Property number six, proteins diversify the properties of cell membranes. And this is what I mentioned earlier. So basically, proteins create many additional functions. For instance, it's the proteins that play a role in transport and they actually selectively choose what enters the cell and what doesn't.