Question

Why is plasma membrane referred to as a selectively-permeable membrane ? Give two points of difference between diffusion and osmosis.

CBSE Class IX Science SA 2 (3 Marks)

Answer 1

Plasma membrane allows selected substances to enter the cell. So it is referred to as selectively permeable membrane


Osmosis is the process by which the water molecules pass through a membrane from a region of higher concentration to lower concentration

Answer 2

Plasma membrane regulates entry and exit of materials across it. Hence, it is referred to as selectively permeable membrane.

S.No.                         Diffusion                                Osmosis

1.              Spontaneous movement of            Movement of solvent from
              substances from a region of             higher concentration to lower 
             high concentration to a region            concentration.
             where its concentration is low.

2.         Semi - permeable membrane is          Movement takes place through
            not required.                                       a semi - permeable membrane.