Q. 2. Why is the plasma membrane called a selectively permeable membrane?
The plasma membrane called a selectively permeable membrane because it relatively allows the movement of substances from the inside of the cell to the outside and vice-versa.
This selectivity depends on the requirements of the cell and the substances present in the surroundings of the cell.
Plasma membrane is called the selectively permeable membrane because it allows the entry of certain substances, exit of some substances while preventing passage to remaining substances.