Now, what determines the mobility of these proteins? Well, basically, it's the functionality of that protein is the protein attached onto some other component, onto some other structure. Now, for instance, if we look at Rhodopsin, which is basically a photopigment that is found in the retina cells of our body, rhodopsin's functionality depends on its ability to move quickly along the membrane. And so proteins, membrane proteins such as Rhodopsin can actually move at a relatively high rate, which is about the rate of half this quantity. Here, on the other hand, other proteins, because their functionality depends that they basically remain in that single position. In these cases, proteins are relatively mobile.