The physical laws that describe the transfer of energy are the laws of thermodynamics. A cell’s metabolism refers to the combination of chemical reactions that take place within it.

Catabolic reactions break down complex chemicals into simpler ones and are associated with energy release. Anabolic processes build complex molecules out of simpler ones and require energy

catabolic — describes the pathway in which complex molecules are broken down into simpler ones, yielding energy as an additional product of the reaction. metabolism — all the chemical reactions that take place inside cells, including those that use energy and those that release energy. anabolic — describes the pathway that requires a net energy input to synthesize complex molecules from simpler ones. thermodynamics — the science of the relationships between heat, energy, and work.