Coenzyme
A small organic molecule that binds temporarily to an enzyme and is essential for its catalytic activity.
Unit
Dimensionless
In depth
Coenzymes carry chemical groups or electrons between reactions and are chemically changed during catalysis, then regenerated elsewhere. Many are derived from vitamins, which is why vitamin deficiency causes such widespread and specific metabolic failures.
Examples in the real world
NAD⁺ carrying hydride in respiration; coenzyme A carrying acyl groups; FAD derived from riboflavin.