Give Scientific Reasons:

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1. Oxygen is necessary for complete oxidation of glucose.

1. In the absence of oxygen, only glycolysis and fermentation can take place.
2. During glycolysis and fermentation glucose is not completely oxidised.
3. For complete oxidation of glucose tricarboxylic acid cycle and electron transfer chain are necessary.
4. Both of these reactions cannot be completed in the absence of oxygen.
5. Therefore, oxygen is necessary for complete oxidation of glucose.

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2. Fibres are one of the important nutrients.

1. We cannot digest fibres but they are important for our digestive health.
2. They help in the digestion of other substances.
3. They also help in the process of egestion of undigested food.
4. Hence, fibres are one of the important nutrients.

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3. Cell division is one of the important properties of cells and organisms.

1. New organism is formed from an existing one due to cell division.
2. It is important for the growth of an organism.
3. It helps to restore the emaciated body and healing wounds.
4. It is necessary for gamete production.
5. Hence, cell division is one of the important properties of cells and organisms.

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4. Sometimes, higher plants and animals too perform anaerobic respiration.

1. Aerobic respiration requires oxygen.
2. Sometimes when there is depletion in the oxygen level in the surrounding, higher plants and animals perform anaerobic respiration.
3. During exercise demand of energy increases, at such times, our muscle cells too perform anaerobic respiration.
4. During germination, when the seeds are submerged under water the oxygen supply is cut off and so they perform anaerobic respiration.

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5. Krebs’ cycle is also known as citric acid cycle.

1. Krebs’ cycle involves a series of cyclic chain reactions.
2. In the beginning, the acetyl co-A molecule, produced in glycolysis, reacts with oxaloacetic acid to produce a 6 carbon compound called citric acid.
3. Hence, Krebs’ cycle is also known as citric acid cycle.

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