And that implies that the plasma membrane is asymmetric. So the two leaflets, the two sides of the membrane are structurally and functionally not the same. Now, what factors contribute to the asymmetry of the plasma membrane? So we have to consider three things. Number one is there is a difference in the composition of the proteins and lipids and carbohydrates found on the two sides of the membrane. So for instance, in this particular case, we have glycolipids and glycoproteins on this side that we don't find on the other side.