Question

Tick the correct answer (A) The bread or idli dough rises because of (1) heat (2) grinding (3) growth of yeast cells (4) kneading.
(B) The process of conversion of sugar into alcohol is called (i) nitrogen fixation (ii) moulding (iii) fermentation (iv) infection.

Answer 1

Hint :Yeast cells are microorganisms which are responsible for catalyzing certain types of chemical reactions. The yeast cells grow and respire which then releases carbon dioxide $ (C{{O}_{2}}) $ . Fermentation is the process by which sugar molecules are converted into ethanol and carbon dioxide in the presence of yeast as enzymes.

Complete Step By Step Answer:
The bread or idli dough rises because of growth of yeast cells. Yeast cells are microorganisms which are responsible for catalyzing certain types of chemical reactions. The yeast cells grow and respire which then releases carbon dioxide. This released carbon dioxide is trapped by dough and makes it rise by the formation of bubbles. Therefore, Option (3) is correct.
In contrast other option includes heat, grinding and kneading which doesn’t evolve carbon dioxide and thus not causes the bread or idli dough rises
The process of conversion of sugar into alcohol is called fermentation which takes place in the presence of yeast as an enzyme. This is illustrated in the following diagram:
 $ {{C}_{6}}{{H}_{12}}{{O}_{6}}\to 2{{C}_{2}}{{H}_{5}}OH+2C{{O}_{2}} $
The above reaction takes place in the presence of yeast as a catalyst. In the reaction, one mole of glucose gives two moles of ethanol and two moles of carbon dioxide.
Therefore, Option (iii) is correct.

Note :
It is important to mention that the bread or idli dough rises because of growth of yeast cells. The released carbon dioxide is trapped by dough and makes it rise by the formation of bubbles. The process of conversion of sugar into alcohol is called fermentation which takes place in the presence of yeast as an enzyme.