Question

STRUCTURED/APPLICATION/SKILL TYPE
The following diagram refers to an apparatus which is used to demonstrate a physiological process :
(a) What is the purpose of keeping potassium hydroxide solution in the test tubes X and Y?
(b) Why has the coloured water risen in tube 1?
(c) What is the purpose of keeping boiled peas soaked in a disinfectant in test tube Y?
(d) Name the biological process which causes the above rise.
(e) Define the biological process shown in the experiment.

Answer 1

a. Potassium hydroxide is kept in the test tubes X and Y because it reacts chemically with the carbon dioxide and absorbs it to form a precipitate.

b. The coloured water rises in tube 1 due to the development of a partial vacuum inside it. This happens because the carbon-dioxide released by the germinating seeds will be soaked by potassium hydroxide present in the flask containing those seeds. This soaking of CO${}_2$ will develop partial vacuum which sucks the water up and hence the water level rises.

c. The boiled peas soaked in a disinfectant in test tube Y are used as a control. In this test tube, the process of respiration will not take place as the peas are boiled while in test tube X, the process of respiration will take place.

d. The biological process which causes the above rise is cellular respiration.

e. Cellular respiration is the process by which energy is released from the breakdown of organic substances (glucose). This process occurs inside the mitochondria. It is exactly opposite to the process of photosynthesis.