Question

RBC and a plant cell(with thick cell wall) are placed in distilled water. The solute concentration is same in both the cells. What changes would be observed in them?

• A. Both plant cell and RBC would not undergo any change.
• B. The RBC would increase in size and burst while the plant cell would remain about the same size.
• C. The plant cell would increase in size and burst while the RBC would remain about the same size.
• D. Both plant cell and RBC would decrease in size and collapse.

Answer 1

The correct option is B The RBC would increase in size and burst while the plant cell would remain about the same size.

Osmosis is the movement of across a semi permeable membrane driven by osmotic pressure gradient. Water moves from region of high osmotic pressure to that of lower one. Plasma membrane is highly permeable to water since water can move by simple diffusion through lipid bilayer and partly to protein channels. Owing to presence of metabolites and salts, cell’s interior is always hypertonic as compared to distilled water. Hence, when placed in distilled water, water will enter through the cell membrane of RBC causing it to increase in size and swell. This makes options A, C and D incorrect. Plant cells are surrounded by rigid cellulosic cell wall which is impermeable to water. Hence there would not be any change in volume of plant cell. This makes option B correct answer.