Definition
Catabolism
Catabolism is the degradative half of metabolism: the set of enzyme-catalysed reactions that break complex biomolecules down into simpler products, releasing energy.
Formally, for a substrate
degraded into products , with the released free energy captured in a carrier such as ATP. The negative
makes catabolic reactions spontaneous in the thermodynamic direction; their rate, not their favourability, is what enzymes control.