The main byproduct of cellular respiration is carbon dioxide (CO2). This biochemical process occurs in both plant and animal cells and involves breaking down glucose to produce usable energy in the form of ATP (adenosine triphosphate). In addition to carbon dioxide, water is also produced as a byproduct. Cellular respiration typically takes place in three main stages: glycolysis, the Krebs cycle, and the electron transport chain. This process is essential for energy production to support cellular functions.