Inhibitor
A substance that decreases the rate of a chemical reaction.
Unit
Dimensionless
In depth
Inhibitors act by blocking active sites, scavenging reactive intermediates or raising the effective activation energy. In enzyme systems, competitive inhibitors bind the active site itself while non-competitive inhibitors bind elsewhere and change the enzyme's shape. Many drugs are enzyme inhibitors.
Examples in the real world
Antioxidants preventing food from going rancid; aspirin inhibiting cyclooxygenase; cyanide blocking cytochrome oxidase.