Oxygen is needed to help the process of turning glucose into ATP. The initial step releases just two molecules of ATP for each glucose. The later steps release much more ATP. Most of the reactions of cellular respiration are carried out in the mitochondria.
The reactions of cellular respiration begin in the cytoplasm, but most of the reactions occur in the mitochondria.All organisms respire to release energy to fuel their living processes.
For us humans it is important as your body cells use the oxygen you breathe to get energy from the food you eat.
