Why is oxygen necessary for cellular respiration?
The method of harvesting energy from the food by the cells is cellular respiration. Cellular respiration occurs in two ways. One way is aerobic respiration and anaerobic respiration. Aerobic cellular respiration is a process in which the chemical energy stored in glucose produces ATP or adenosine tri phosphate. ATP molecule is used by the cell as source of energy for metabolic processes. There is transfer of energy from glucose to ATP in cellular respiration. Aerobic respiration comprises of three stages called glycolysis, Kreb’s cycle and electron transport. The process of breakdown of glucose into several intermediate substances release energy molecules like ATP and NADPH2.
Cellular respiration utilizes oxygen at the end of electron transport. The electrons to reduce the oxygen molecule into water molecule are provided by the intermediate products, and are transferred to oxygen through electron transport cycle. Oxygen is used by the respiratory metabolic reaction in the following way.
C6H12O6 +6O2 Ãƒ¯Ã†’Ã‚ 6CO2 + 6H2O + Energy
In the electron transport chain that occurs on the inner membrane of the mitochondria, there are several electron carriers present. These electron carriers get reduced by accepting an electron and get oxidized when an electron is donated to the next carrier molecule. The electron that is transported through several carriers reach the oxygen molecule at the end to reduce it and convert it into water molecule. Oxygen is the final electron acceptor in cellular respiration and results in the formation of water. This reaction also releases an ATP molecule. The total amount of energy that is released in the cellular respiration in eukaryotic organisms is calculated in the form of number of ATP molecules. The total number of ATP molecules produced as energy from cellular respiration (glycolysis + Kreb’s cycle + electron transport) is 36. If oxygen is not provided to the respiratory process, like in aerobic respiration, pyruvic acid undergoes fermentation to produce alcohol and carbon-di-oxide. In this reaction only two ATP molecules are released compared to 36 released in aerobic process.