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-

choline

 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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