Respiration releases energy – it is an exothermic process.
Photosynthesis is the process by which plants, and some bacteria, synthesise food molecules – which they then use, in addition to other things, for respiration. The process of photosynthesis requires energy – it is endothermic.
Don't confuse respiration with breathing, which is ventilation. Respiration happens in cells.
All organisms need energy to live. This energy is used:
Respiration is only around 40 per cent efficient. As animals respire, heat is also released. In birds and mammals, this heat is distributed around the body by the blood. It keeps these animals warm and helps to keep a constant internal temperature.
Energy is also used: