The relationship between photosynthesis and cellular respiration is such that the products of one process are the reactants of the other. Photosynthesis is the process whereby carbon dioxide and water react, using energy from sunlight, to produce glucose and oxygen. In cellular respiration, the glucose combines with oxygen to produce carbon dioxide.
These two cycles depend on one another for the entire cycle to take place, which ensures that life continues to survive. Photosynthesis provides oxygen for all living organisms and for the process of cellular respiration. Cellular respiration requires oxygen to make adenosine triphosphate, or ATP, which is a high-energy molecule. It also releases carbon dioxide into the atmosphere, which is used by plants and bacteria to process carbon dioxide back into oxygen.
Photosynthesis is used by plants and other organisms to convert sun energy to chemical energy. This chemical energy is stored in the form of glucose, which is used to provide energy for organisms. This energy stored in plants is harvested through cellular respiration to form ATP, which provides energy needed for many biological processes, such as muscle contraction and synthesizing molecules.
The life cycle of photosynthesis and cellular respiration sustains life on earth. Both are required to exist in symbiosis. Cellular respiration cannot occur without photosynthesis, and vice versa.