Cellular respiration primarily occurs in the mitochondria, often referred to as the "powerhouses" of the cell. This organelle plays a crucial role in converting the energy stored in food molecules into adenosine triphosphate (ATP), which cells use as a direct energy source for various functions. The mitochondria utilize oxygen and glucose in this process to produce energy-rich ATP, while also generating by-products like carbon dioxide and water. Efficient cellular respiration is essential for maintaining cellular and organismal health, providing energy necessary for growth, repair, and maintenance of biological systems.