Question

During breathing we inhale oxygen. Why does our cells need oxygen? What happens with that oxygen?

Answer 1

Just like we breathe,our cells need to breathe as well to perform the vital physiological activities of our body necessarily.
The cells utilise that oxygen in their respiration(cellular respiration) to create energy essential to perform those vital activities in our body.

Answer 2

Answer:

The oxygen is inhaled air passes across the thin lining of the air sacs and in the blood vessels .The oxygen is then carried around the body in the bloodstream ,reaching every cells .