The gas produced during respiration is carbon dioxide (CO2). During cellular respiration, organisms break down glucose molecules to release energy. This process occurs in the cells of living organisms, including plants, animals, and fungi. Oxygen is consumed during this biochemical process, and carbon dioxide is released as a byproduct. The exchange of gases—oxygen taken in and carbon dioxide expelled—occurs in various biological processes, primarily within the lungs of animals and the leaves of plants during photosynthesis. In this way, respiration plays a crucial role in energy production and maintaining the balance of gases in the atmosphere.