The gas released during respiration is carbon dioxide (CO2). During cellular respiration, cells convert glucose and oxygen into energy, producing carbon dioxide and water as byproducts. This process occurs in the mitochondria of cells and is essential for generating the energy needed for various cellular functions. Carbon dioxide is then transported from the cells to the lungs via the bloodstream, where it is expelled from the body when we exhale. This continuous cycle of oxygen intake and carbon dioxide output is vital for maintaining life and supporting metabolic processes.