Aerobic respiration requires a continuous supply of oxygen from the air or water surrounding the organism. Oxygen that is taken in is delivered by the blood circulatory system to the body cells. In the cells, glucose molecules are oxidised by oxygen to release energy. Aerobic respiration can be summarised by the following chemical equation:
Aerobic respiration involves the oxidation of glucose in the presence of oxygen to carbon dioxide, water and energy. Organisms that respire aerobically are called aerobic organisms. Aerobic respiration releases all the available energy stored within the glucose molecules. The entire process does not only involve a single chemical reaction, but also driven by a sequence of complex biochemical reactions which are catalysed by the respiratory enzymes. The energy stored within the glucose molecules are released gradually. This is far more useful to the organism than a sudden release of energy.
Only a small portion of energy is lost in maintaining the body temperature. A larger portion of the energy is used to synthesise ATP from ADP and inorganic phosphate. ATP which is an instant source of energy is the main supply for all living cells. Each ATP molecule consists of three phosphate groups and the phosphate bonds can be easily broken down to release energy.
During vigorous exercise such as running a race, the muscles initially respire aerobically. However, the muscles soon used up all the available oxygen. In spite of the increased breathing rate and heartbeat rate, the blood cannot supply oxygen fast enough to meet their requirements. The rate at which oxygen is used by the muscles exceeds the amount of oxygen supplied by the blood. The muscles are in a state of oxygen deficiency, and an oxygen debt is incurred. As such, the muscles obtain extra energy from anaerobic respiration because oxygen is not available. During anaerobic respiration, the...