Question

A candidate in order to study the process of osmosis has taken 3 potato cubes and put them in 3 different beakers containing 3 different solutions. After 24 hours, in the first beaker the potato cube increased in size, in the second beaker the potato cube decreased in size and in the third beaker there was no change in the size of the potato cube. The following diagram shows the result of the same experiment:

(i) Give the technical terms of the solutions used in beakers, 1,2 and 3.

(ii) In beaker 3 the size of the potato cube remains the same. Explain the reason in brief.

(iii) Write the specific feature of the cell sap of root hairs which helps in absorption of water.

(iv) What is osmosis ?

(v) How does a cell wall and a cell membrane differ in their permeability ?

Answer 1

(i) Beaker 1: Hypotonic solution

Beaker 2: Hypertonic solution

Beaker 3: Isotonic solution

(ii) In beaker 3 the size of potato cube remains the same because of isotonic solution which has same concentration of solutes as that of potato cells. So water is neither lost or gained by the potato cells.

(iii) Cell sap of root hairs is much more concentrated than the soil solution and this causes entry of water into the root cells.

(iv) Osmosis is the movement of water molecules from a more dilute solution to a less dilute solution, through a semi-permeable membrane.

(v) Cell wall is freely permeable while cell membrane is selectively permeable.