Exothermic Reaction: Reactions or processes that release energy into the surrounding, either in the form of heat or light, are known as exothermic reactions. Overall release of energy from the system occurs when the total energy of the products formed is less than the total energy of the reactants. It is the exact opposite of an endothermic reaction.
Respiration: Respiration or Cellular respiration is a biochemical process in which the cells of an organism obtain energy needed to perform their functions by combining oxygen and glucose to form the energy currency of cells called ATP along with the release of carbon dioxide and water.
C6H1206 (Glucose) + O2 -> CO2 + H20 + ATP
Energy is required to support life. We obtain that energy from food sources. Glucose is obtained from molecules of food that are broken down into simplest carbohydrates during digestion. Oxygen is taken from the air via Lungs. Oxygen and Glucose then combine in the cells and convert the chemical energy into heat energy in the form of Adenosine Triphosphate that is used up by cells to perform their functions. Carbon Dioxide and Water are released as by-products.
Since energy is released in the whole process, it is considered as an exothermic process.