What is the defenition of respiration?

Answer 1

Respiration is the production of energy from food via a chemical reaction.

In all the different forms of respiration, the 6-Carbon molecule of glucose is first converted to a 3-Carbon molecule of Pyruvate, which occurs in the cytoplasm of the cell.

Main forms of respiration are:

Aerobic respiration (Abundant Oxygen)

Pyruvate + Oxygen -> Carbon dioxide + Water + Energy (in the form of ATP)

This occurs in the mitochondria of the cell. The 3-Carbon pyruvate is converted fully to 3 molecules of carbon dioxide (which has only one molecule of Carbon).

Anaerobic Respiration (Lack of/Less amount of Oxygen, usually mammalian)

Pyruvate -> Lactic acid + Energy (in the form of ATP)

This occurs in our muscles, when we run suddenly without warm-up, etc. Due to the lack of oxygen in such a sudden movement, the pyruvate converts to lactic acid (which is still a 3-Carbon molecule) in the muscles, which causes cramps.

Anaerobic respiration (No Oxygen)

Pyruvate -> Ethanol + Carbon dioxide + Energy (in the form of ATP)

This usually occurs in organisms like yeast. This is the fermentation process. The pyruvate is converted to a 2-carbon alcohol, which is ethanol, and the remaining carbon molecule forms carbon dioxide.

The first aerobic respiration releases the most amount of energy, about 36 ATP. The lactic acid respiration produces a little less energy. The anaerobic respiration forming ethanol releases energy of only about 2 ATP.

Answer 2

Respiration is the process by which living organisms take in oxygen and release carbon dioxide. In humans, this process occurs in the lungs where oxygen is taken up by red blood cells and transported to tissues for energy production, while carbon dioxide is expelled from the body.