Question: why do we need oxygen?

Lauren Laing answered on 8 Mar 2016:

Oxygen is brought into the body via the lungs when we breathe in. This is then transported by the red blood cells to the entire body. Every cell in your body uses a process called respiration in order to release energy for the cell to grow and repair. During the process of respiration, oxygen is needed to burn the fuels in the cell (sugars and fats) in order to produce this energy.