Catalyst

A substance that speeds up a chemical reaction but is not consumed or altered in the process. Catalysts are of immense importance in chemistry and biology. All enzymes are catalysts that expedite the biochemical reactions necessary for life. The enzymes in saliva, for example, accelerate the conversion of starch to glucose, doing in minutes what would otherwise take weeks. The word “catalyst” was introduced into science by the great Swedish chemist Jons Jakob Berzelius (1779-1848) who also determined the atomic and molecular weights of thousands of substances, discovered several elements including selenium, first isolated silicon and titanium, and created the present system of writing chemical symbols and reactions.

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A substance that accelerates a chemical reaction but is not consumed or changed permanently thereby. SYN: catalyzer.

- inorganic c. a c. such as a finely divided metal (Pt, Rh), carbon, etc.

- negative c. a c. that retards a reaction.

- organic c. 1. SYN: enzyme, ribozyme. 2. a c. that is an organic molecule.

- Raney c. SYN: Raney Nickel.

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cat·a·lyst 'kat-əl-əst n a substance (as an enzyme) that enables a chemical reaction to proceed under different conditions (as at a lower temperature) than otherwise possible

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n.

a substance that alters the rate of a chemical reaction but is itself unchanged at the end of the reaction. The catalysts of biochemical reactions are the enzyme.

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cat·a·lyst (katґə-list) any substance that brings about catalysis; called also accelerant.