A chemical reaction which releases energy either in form of heat or light is scientifically termed as exothermic reaction, on the other hand chemical reactions which absorb heat during the due course of reaction is termed as Endothermic reaction.
Respiration is the complete biological process of breathing in of oxygen and giving out of Carbon dioxide. In a deeper level with more biological knowledge, we can define respiration as the process by which living cells use oxygen to breakdown sugar and obtain energy and it is during this course of time that heat is given out as a by product and the chemical process of breathing is termed as an exothermic reaction.
Chemical reaction of respiration:
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
One glucose molecule reacts with six oxygen molecules to produce six carbon dioxide molecules which is again exhaled through the lungs, six water molecules and energy this complex reaction takes place inside the human body during the process of respiration. Basically, oxidation of glucose takes place to produce a large amount of energy. The energy released in this process is released in form of ATP (Adenosine triphosphate) which can further be used in various cell activity according to the need and eventually provides the body with energy which it requires to stay active.