Respiration occurs in the mitochondria, which are often referred to as the "powerhouses" of the cell. These organelles are responsible for converting nutrients into adenosine triphosphate (ATP), the energy currency of the cell. During cellular respiration, glucose and oxygen are utilized to produce ATP, carbon dioxide, and water. This process is vital for providing the energy required for various cellular functions. Mitochondria have their own DNA and are believed to have originated from ancient symbiotic bacteria, highlighting their importance not just in energy production but also in cellular evolution.