Cellular respiration is the process by which the food is broken down and energy is generated, in the form of ATP molecules. It is termed aerobic respiration, when oxygen is present; otherwise, it is known as anaerobic respiration (or fermentation). Aerobic cellular respiration is much more efficient process as compared to fermentation, in terms of energy produced per molecule of glucose consumed.
Aerobic cellular respiration takes place inside our cells (except for probably muscle cells, where fermentation takes place, especially during exercise or strenuous labor), in organelles known as mitochondria, which is also known as the power house of the (eukaryotic) cell. The process of aerobic cellular respiration consumes the oxygen that we breathe in and generates carbon dioxide (which is exhaled from our body) and water, along with ATP.
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