Cell membrane

Cell membrane

Definition : it is a protective sheath, and it is also known as plasma membrane, plasmalemma. This membrane separate ICF from ECF. it is a semipermeable membrane. Thickness of the cell membrane 75-111°A.

Composition of cell membrane :

1. Protein - 55%
2. Lipid - 40%
3. Carbohydrate - 5%

Lipid layer of cell membrane : 

1. Phospholipid.
2. Cholesterol .

Protein layer of cell membrane :

1. Integral protein - that pass through entire thickness of cell membrane from one side to other side.

Example of integral protein:  

1. Cell adhesion proteins.
2. Cell junction protein.
3. Some carrier or transport protein.
4. Channel protein.
5. Some hormones receptor.
6. Antigens.
7. Some enzymes.

2. Peripheral protein - are the partially embedded in the outer or inner surface of the cell membrane .

Example of peripheral protein :

1. Proteins of cytoskeleton.
2. Some carrier or transport protein.
3. Some enzymes.

Functions of cell membrane :

1. Protective function .
2. Selective permeability .
3. Absorptive function.
4. Excretory function .
5. Exchange of gases.
6. Maintenance of shape and size of the cell.
7. Transportation.

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