Thermodynamics
Thermodynamics tells us that every transformation of matter chemical transformation is accompanied with energy conversion .For example when complex molecules are broken down to their simpler constituent molecules they liberate kinetic energy. Thus catabolic processes are energy releasing or exergonic . conversely, when complex molecules are synthesized from simpler ones they consume or lock potential energy. Hence anabolic processes are energy conversing endergonic .In this context metabolism can be defined as the sum total of all of all energy gain and release processes in a living cell.