The Krebs cycle is a complex series of chemical reaction that produce CO2 and ATP. This happens through the linking of 2 carbon coenzymes with Carbon compounds. The newly created compound then goes through a series of changes that result in energy. This process occurs in all oxygen utilizing cells as a respiration process. CO 2 plays an important role to the environment and other biological processes such as this one because it creates the stimulus to brethe for organisms such as ourselves. Then ATP provides cells the energy to synthesize proteins from amino acids and replicate DNA. In conclusion, this process is the major source of energy in all living organisms, whether it be plants or humans.