Structure And Function Of Cell Membrane
Question 1. Describe the fluid mosaic structure of cell membrane.
Answer.
Structure Of Cell Membrane/Fluid Mosaic Model Of Cell Membrane Membrane
- The fluid mosaic model proposed by Singer and Nicholson (1972) is the most acceptable model for membrane structure
- The membranes are composed of lipids, carbohydrates and proteins
- The actual composition differs from tissue to tissue
- Among the lipids, amphipathic lipids (containing hydrophobic and hydrophilic groups) namely phospholipids, glycolipids and cholesterol are found in the membrane
- The biological membranes have a thickness of 5 to 8 nm
- A membrane is essentially composed of a lipid bilayer
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- Membrane proteins are categorized into 2 groups
- Extrinsic proteins – these are peripheral membrane proteins which are loosely held to the surface of the membrane and they can be easily separated eg. Cytochrome C of the mitochondria
- Intrinsic proteins – these are integral proteins which are tightly bound to the lipid bilayer and can be separated only by the use of detergents or organic solvents eg. hormone receptors and cytochrome
- The membrane is asymmetric due to the irregular distribution of proteins
- The lipid and protein subunits of the membrane give an appearance of mosaic or ceramic tile
- Unlike a fixed ceramic tile the membrane changes; hence the structure of the membrane is considered as fluid mosaic
Fluid Mosaic Model
Question 2. Functions Of Cell Membrane.
Answer.
Functions Of Cell Membrane:
- It separates and protects the cell from the external hostile environment
- The plasma membrane provides a connecting system between the cell and its environment
- It acts as a semi permeable membrane
- Absorptive function
- Excretory function
- Exchange of gases
- Maintenance of size and shape of the cell .
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