Why the cell membrane model is called “fluid mosaic model”

Yeah, why “fluid”, why “mosaic”?

Let’s look at our model of the membrane again. The basic membrane is the double phospholipid layer and the proteins and carbohydrates are just add-ons.

So what makes this a fluid mosaic model?

Well, the fluid that is being referred to is the fluidity of the phospholipid bilayer. Each of the phospholipid molecule here can change places with each other side to side. Sometimes, they can even change places in to out or vice versa.

Because of the fluidity of the phospholipid bilayer, the proteins embedded in them can also change places. They can be clumped in one section or they can be spread out in another. Since the membrane is very dynamic, there is constant motion of molecules making it up. Thus, the membrane that one sees at one time is not exactly the same membrane at another time. This is the reason why the membrane is “mosaic”.

So the “fluidity” of the membrane is due to the phospholipid molecules while the “mosaicity” is due to the proteins.