Question

In the test tubes A and B shown below, yeast was kept in sugar solution. Which products of respiration would you expect in tubes A and B?


​Give reason for your answer.

Answer 1

Test tube A:

1. There is a oil film that separates the atmosphere from sugar solution.
   
2. This is why in the ​sugar solution of test tube A, there is an anaerobic environment.
3. In the absence of oxygen, but the presence of sugar, the anaerobic respiration takes place in yeast cells present in this test tube A.
   
4. In this process, sugar is used by the yeast cells to produce ethanol and carbon dioxide, along with the generation of energy.
   

Glucose→Pyruvate →2C2H5OH +2CO2 + 2ATP

Test tube B:

1. The sugar solution is exposed to the atmospheric gasses.
2. This makes it easier for oxygen to enter the solution.
   
3. In the presence of oxygen and sugar, aerobic respiration occurs in the yeast cells present in test tube B.
   
4. In this process, sugar is used by the yeast cell to produce carbon dioxide, water and energy.
   

Glucose→Pyruvate→6CO2 +6H2O + 38ATP