Question

Question 2
What are the different ways in which glucose is oxidised to provide energy in various organisms?

Answer 1

At first glucose (6 carbon molecule) is broken in the cytoplasm of the cells of all organisms. This process yields a 3 carbon molecule compound called Pyruvate. Further, break down of 3 carbon pyruvate takes place in different ways in different organisms.

Anaerobic Respiration: This process takes place in the absence of oxygen, e.g. in yeast during fermentation. In this case, pyruvate is converted into ethanol and carbon dioxide.
Aerobic Respiration: In aerobic respiration, the breakdown of pyruvate takes place in presence of oxygen to give rise to 3 molecules of carbon dioxide and water. The release of energy in aerobic respiration is much more than anaerobic respiration.
Lack of Oxygen: Sometimes, when there is lack of oxygen, especially during vigorous activity in our muscles, pyruvate is converted into lactic acid (3 carbon molecule compounds). Formation of lactic acid in muscles causes cramp in the muscles.