The process by which living organisms convert nutrients into energy is known as cellular respiration. This metabolic process takes place in the cells, where glucose derived from ingested food is broken down in the presence of oxygen. The primary products of this chemical reaction are carbon dioxide, water, and adenosine triphosphate (ATP), which provides energy for various cellular functions. In anaerobic conditions, some organisms can undergo fermentation, which also produces energy but less efficiently than aerobic respiration.