Explain the three pathways of breakdown in living organisms.
The breakdown of sugar can be shown by following diagram:
In all organisms, glucose is first converted into pyruvate. Glucose is a 6-carbon molecule, while pyruvate is a 3-carbon molecule.
This step is same in all organisms and it happens in cytoplasm. Further breakdown of pyruvate can happen in any of the following ways:
In Yeast: In yeast, breakdown of pyruvate take place in absence of oxygen. Due to this, it is called anaerobic respiration. Pyruvate is broken down into ethanol and carbon dioxide.
In muscle cells: During strenuous physical activity, the energy demand from muscle cells suddenly increases. This is compensated by anaerobic respiration in muscle cells. In such a situation, pyruvate is broken down into lactic acid.
In mitochondria: In this case, breakdown of pyruvate takes place in presence of oxygen. Due to this, it is called aerobic respiration. Pyruvate is broken down into carbon dioxide and water. Aerobic respiration is the norm is most of the living beings.
