Question

Mixture of yeast, sugar and water was taken in a test tube. After one hour, bubbles were observed in the mixture. The formation of bubbles was due to

• A. Photosynthesis
• B. Digestion
• C. Respiration
• D. Excretion

Answer 1

The correct option is (B):

Explanation of the correct option:

1. Yeast is a eukaryotic fungi which performs anaerobic respiration.
2. The bubbles that are formed in the test tube are due to the formation of carbon dioxide during respiration.
   
3. Yeast is using up the sugar to produce ethanol and carbon dioxide during respiration as the process occurs in the absence of oxygen.

Explanation of the incorrect options:

Option (A):

1. Digestion is the enzymatic process of breaking down the nutrients present in food into simpler forms.
   
2. It does not occur here as digestion does not produce the gaseous components like carbon dioxide. ​

Option (C):

1. Excretion is the process of removal of undigested materials.
   
2. Excretion does not occur here forming gasses. ​

Option (D):

1. Photosynthesis is the process of production of glucose from carbon dioxide and water.
   
2. Photosynthesis requires the presence of a green pigment called chlorophyll which can trap the sunlight,, but it is not present in Yeast. ​

Final Answer: The formation of bubbles was due to respiration.