Glucose is first broken down in the cell cytoplasm into a three carbon molecule called pyruvate. Pyruvate is further broken down by different ways to provide energy.
The breakdown of glucose by different pathways can be illustrated as follows.
→ Anaerobic Respiration: This process takes place in 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, breakdown of pyruvate takes place in presence of oxygen to give rise 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.
