Carry out the following osmosis experiment:
Take four peeled potato halves and scoop each one but to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water. Now,
(a) Keep cup A empty
(b) Put one teaspoon sugar in cup B
(c) Put one teaspoon salt in cup C
(d) Put one teaspoon sugar in the boiled potato cup D.
Keep these for two hours. Then observe the four potato cups and answer the following:
(i) Explain why water gathers in the hollowed portion of B and C.
(ii) Why is potato A necessary for this experiment?
(iii) Explain why water does not gather in the hallowed out portions of A and D.

AcademicBiologyNCERTClass 9

(i) Water gathers in the hollowed portion of B and C because, in both B and C cases, a concentration difference is formed inside the trough and water in the cup (where potato scoops are placed). Therefore, when the endosmosis process takes place, water enters into the hollow portion of the potato, and the potato wall acts as a semipermeable membrane.

(ii) Potato cup A is essential for this experiment as it acts as a control and provides a comparison with situations formed in potato cups B, C, and D. Cup A does not contain anything, therefore it does not encourage the movement of water due to an external substance.

(iii) Water does not get accumulated in the hollow portion of A and D because cup A does not possess the concentration difference required for the movement of water, thus for osmosis. 

In cup D, potato cells are boiled, therefore cells become dead. These dead cells do not act as a semipermeable membrane to encourage the process of osmosis.

Osmosis is a passive process that involves the movement of molecules from a region of higher concentration to a region of lower concentration until the concentrations become equal on either side of the membrane. Any solvent can undergo the process of osmosis, including gases and supercritical liquids.

Plasmolysis is the process that takes place when the plant cell losses cytoplasmic water due to osmosis and shrinks in size. Plasmolysis is the process of shrinkage or contraction of the cell contents away from the cell wall when a living plant cell loses water through osmosis. The process of plasmolysis does not occur in dead cells.

It occurs when the plant's cell is placed in a hypertonic solution or solution having a higher concentration of salts. Cytoplasm loses its water to the hypertonic solution to achieve equilibrium and shrinks.]

Updated on 10-Oct-2022 12:47:40