Question

What will happen if a cell is placed into 0.4 % \[\](mass/volume) $\text{NaCl}$ solution?
 (A) There will be no change in cell volume
 (B) Cell will dissolve
 (C) Cell will swell
 (D) Cell will shrink

Answer 1

Hint: Protoplasmic solution of a cell is isotonic (solution having same osmotic pressure) to 0.9 % (mass/volume) $\text{NaCl}$ (sodium chloride) solution.
Cell membrane is a semipermeable membrane.

Complete Solution :
- When the two solution having different osmotic concentration are separated by mean of a semipermeable membrane the molecules of solvent or water moves from the region of high diffusion pressure (or high concentration) to the region of their low diffusion pressure (or low concentration) this movement of water or solvent is called osmosis.
- So, if we place a cell into a 0.4 % $\text{NaCl}$ solution which acts as a hypotonic solution in respect to the cell solution. So a concentration gradient is developed in between the cell solution and surrounding solution across the cell membrane. So there is movement of water that takes place in between the cell and its environment, until the equilibrium is not established.
(A) - Volume of the cell increases due to endosmosis, so this option is not correct.
(B) - Due to the difference in osmotic pressure across the cell membrane cell volume will change, but the cell will not disappear. So this option is not correct.
(C) -When a cell placed in a hypotonic solution the water will move from cell surrounding to into the cell due to endosmosis. As a result the cell volume is increased and finally the cell swells up. So this option is correct.
(D)- Due to endosmosis cell volume will increase, so this option is not correct.
So, the correct answer is “Option C”.

Note: In osmosis two solutions must be separated by a semipermeable membrane, and concentration gradient must be present.
- Osmosis term is used to refer diffusion of water molecules across the permeable membrane