Where Are Reactions Catalyzed?

Enzymes have active sites. The enzyme active site is the location on the enzyme surface where substrates bind, and where the chemical reaction catalyzed by the enzyme occurs.

Where is a catalyst in a reaction?

A catalyst will appear in the steps of a reaction mechanism, but it will not appear in the overall chemical reaction (as it is not a reactant or product). Generally, catalysts alter the mechanism of the reaction in a substantial way such that the new barriers along the reaction coordinate are significantly lower.

Where is catalyzed found?

Enzyme catalysis is the increase in the rate of a process by a biological molecule, an "enzyme". Most enzymes are proteins, and most such processes are chemical reactions. Within the enzyme, generally catalysis occurs at a localized site, called the active site.