Cells/The Plasma Membrane

The Plasma Membrane

The thin plasma membrane surrounds the cell, separating its contents from the surroundings and controlling what enters and leaves the cell. The plasma membrane is composed of two main molecules, fats (in fact phospholipids) and proteins. The fats are arranged in a double layer with the large protein molecules dotted about in the membrane (see diagram 3.4). Some of the protein molecules form tiny channels in the membrane while others help transport substances from one side of the membrane to the other.

Diagram 3.4 The structure of the plasma membrane

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