Introduction:

All living things need energy for all metabolic activities:

Respiration is defined as the exchange of environmental oxygen with Carbon dioxide produced in body.

And this reaction is called (oxidation of food) reaction.

Respiration involves 5 step:

1. Intake of oxygen (Breathing)
2. Oxidation of food
3. Release of Co₂ after oxidation of food
4. Release of energy
5. Storage of this released energy in the form of ATP and its utilization.