Respiration is considered an exothermic reaction because it involves the breakdown of carbohydrates present in food to form glucose. During this process, glucose combines with oxygen in the cells of our body, leading to the production of energy. The breakdown of carbon dioxide in the food also contributes to the release of heat, making respiration an exothermic process.
The overall chemical equation for cellular respiration is commonly simplified as:
C6H12O6 (glucose) + 6O2 (oxygen) → 6CO2 (carbon dioxide) + 6H2O (water) + energy (as ATP)