Catabolism, the breaking down phase of metabolism, provides energy required for anabolism which is the building phase of metabolism. For example, catabolism generates the energy needed for muscle contraction and for growth. Cellular respiration is the catabolic process in which nutrients are broken down and their energy packaged within a special storage molecule called ATP (adenosine triphosphate) for use by the cell. Cellular respiration requires oxygen as well as nutrients.
Anabolism is the building, or synthetic phase of metabolism. During anabolism energy is used to make chemical compounds and structures needed by the cell. These chemical compounds are needed for growth, maintenance and repair of the body.
