So we see that, in addition, asymmetry is also preserved because membranes always arise and grow and extend from preexisting membranes, which are asymmetric to begin with. Now, in our discussion here, we said that the difference in the composition of not only the proteins but also the lipids basically gives this membrane the property of asymmetry. So now let's move on from proteins to lipids. So we know that just like proteins are synthesized and eventually placed into the membrane in an asymmetric fashion, lipids are also synthesized and inserting to the membrane asymmetrically. However, the thing about lipids is, so fossil lipids is they can actually flip flop, they can actually rotate. And so what that implies is, unlike the absolute configuration, unlike the absolute asymmetry of the proteins in the membrane that basically do not change because they cannot flip flop, the asymmetry of the membrane due to the lipids does in fact change over time.