Question

Explain the three pathways of breakdown in living organism .

Answer 1

The process of breakdown of glucose molecules involves two major stages - glycolysis (anaerobic respiration) and aerobic respiration ( Kreb's cycle and ETS Pathway). Cellular respiration begins at this stage in the cytoplasm of the cells, and yields 2 carbon-based molecules called pyruvate, and 2 molecules of ATP.
That can be elaborated as
Fate of Pyruvic Acid: The breakdown of pyruvic acid takes place in mitochondria and the molecules formed depend on the type of respiration in a particular organism. Respiration is of two types, viz. aerobic respiration and anaerobic respiration.

Anaerobic Respiration: This type of respiration happens in the presence of oxygen. Pyruvic acid is converted into carbon dioxide. Energy is released and water molecule is also formed at the end of this process.

Aerobic Respiration: This type of respiration happens in the absence of oxygen. Pyruvic acid is either converted into ethyl alcohol or lactic acid. Ethyl alcohol is usually formed in case of anaerobic respiration in microbes; like yeast or bacteria. Lactic acid is formed in some microbes as well as in the muscle cells.