Cell Plasma membrane
What is Cell or Plasma Membrane?
Ans. Every cell is enclosed in a fine microscopic living selectively permeable membrane known as cell or plasmamembrane or Plasmalemma. It is triple layered (75 º thick) arranged in Protein-Lipid-Protein layers.
What is the ultrastructure of cell membrane?
Ans. Plasma membrane is thin elastic and semipermeable having the following structure:
i) About 75 Aº thick.
ii) Trilayered with an outer Protein (20 Aº thick), middle Phospholipid (35 Aº) and inner protein (20 Aº) layers.
iii) Phospholipid layer can be divisible into two sub-layers. Each sub-layer with a polar end towards the protein layer and an opposite non polar end.
iv) Numerous pores of about 7Aº in diameter are distributed throughout the plasma membrane.
What are the functions of cell membrane?
Ans. The important functions of cell membrane are :
i) Protection of the cell organelles.
ii) Taking part in endocytosis and in the exchange (food, O2, CO2, different ions, etc.) of essential materials.
iii) Maintenance of osmotic balance through diffusion, active transport etc.
iv) Taking part in the formation of cell organelles.
v) Maintenance of intercellular communication.
