The element necessary for respiration in humans is oxygen. Oxygen is a vital gas that is inhaled through the lungs and delivered to the bloodstream, where it is transported to cells throughout the body. Respiration is the process by which cells convert oxygen and glucose into energy, producing carbon dioxide as a byproduct. This energy is essential for all bodily functions, including growth, repair, and daily activities. Without sufficient oxygen, cells cannot perform their functions effectively, which can lead to serious health complications and, if prolonged, can be life-threatening.