Why is plasma membrane also called a selectively permeable membrane? Write any two functions of it.

Hint: The membrane surrounding the cellular organelles by forming a barrier between the cell organelles and its external environment is called a plasma membrane.

Complete Answer:
- The plasma membrane is also known as the cell membrane or cellular boundary. The plasma membrane is labelled as a selectively permeable membrane as it facilitates the movement of only certain molecules through it.
- Not all the molecules are free to diffuse through the cellular surface. If at all, the plasma membrane ruptures or breaks apart, the molecules of certain substance free move in and out from the cells.
- Since the membrane acts as a membrane barrier, exchange of materials from its external surroundings through the process of diffusion or osmosis won’t take place.
- As a result, the cell might die on account of disappearance of the protoplasmic material. This facilitates the hydrophobic molecules and other relevant small polar molecules to diffuse through the lipid layer. However, it does not allow the ions as well as the large polar molecules to diffuse through its membrane.

Any two functions of the Plasma Membrane are,
- The membrane functions as a barrier between the cellular organelles and their outer environment.
- It aids in initiating communication as well signalling between both the cells.

Note: The other functions of plasma membrane are,
- It also helps by anchoring the cytoskeleton in order to provide shape to the cell.
- It helps in maintaining and monitoring the chemical composition of the cell.
- It provides protection to the cell by inhibiting entry of foreign particles.