Tissues

Question

Carry out the following osmosis experiment:

Take four peeled potato halves and hollow each one out 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 boiled potato cup D.

Keep this setup 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 hollowed out portions of A and D.

Answer

a) Water gathers in the hollowed portion of potato B and C because the plasma membrane of potato cup act as semipermeable membrane and the concentration gradient causes the water to move from the cell to the hllowed portion by the process of osmosis.

(b) Potato cup A is necessary as it acts as a control. This shows that osmosis occurs only when there is concentration gradient and a living semi permeable membrane. 

(c) (i) In the potato cup A, there is no concentration gradiesnt for osmosis to occur.

(ii) In the potato cup D, the semi permeability of potato membrane is lost due to boiling. So, no water movement occurs.

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