mosaic properties of cell membranes |
A mosaic is a structure made up of many different parts. Likewise, the plasma membrane is composed of different kinds of macromolecules. The components of a plasma membrane are integral proteins, peripheral proteins, glycoproteins, phospholipids, glycolipids, and in some cases cholesterol, lipoproteins.
In addition to being composed of different components, the relative amounts of these components can vary from membrane to membrane. The table below shows some of the variation in protein, lipid and carbohydrate content of some membranes.
membrane |
% protein |
% lipid |
% carbohydrate |
myelin |
18 |
79 |
3 |
human erythrocyte plasma membrane |
49 |
43 |
8 |
mitochondrial inner membrane |
79 |
24 |
0 |
amoeba plasma membrane |
54 |
42 |
4 |
Not only do membranes vary in the relative amount of lipid they contain, the kinds of lipids in membranes can also vary. In the table below the the proportions of various kinds of lipids in different membranes is shown.
membrane |
cholesterol |
phosphotidyl- |
sphingo- myelin |
phosphotidyl- serine |
glycolipids |
rat liver plasma membrane |
30 |
18 |
14 |
9 |
- |
rat liver RER |
6 |
55 |
3 |
3 |
- |
rat liver nuclear membrane |
10 |
55 |
3 |
3 |
- |
rat liver myelin |
22 |
11 |
6 |
7 |
12 |
E coli cytoplasmic membrane |
0 |
0 |
- |
- |
- |
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