Question

Explain the three different pathways of breakdown of glucose in living organisms.

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Answer 1

Explanation:

Glucose is the most important source of energy for all living things. The food we eat is broken down into carbohydrates, the most important of which is glucose. To provide energy to the body, glucose is oxidised.

Different ways in which glucose breaks down

The following are the various ways in which glucose is broken down.

Aerobic Respiration

In aerobic respiration, breakdown of pyruvate takes place in the 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.

Anaerobic Respiration

The anaerobic respiration process takes place in the absence of oxygen. For example: In yeast during fermentation. In this process, the pyruvate is converted into ethanol and carbon dioxide.

Lack of Oxygen

At times when there is a lack of oxygen in our body, mainly during vigorous activity, in our muscles, pyruvate is converted into lactic acid which is a 3 carbon molecule compound. The formation of lactic acid in muscles causes cramp.

Answer 2

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 the 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 found in most of the living beings.