∞ generated and posted on 2016.12.15 ∞

Substance that speeds up a chemical reaction without itself being used up in the course of the chemical reaction.

Catalysts cause other things to change without themselves changing, somewhat like a tool such as a wrench; a nut would be locked into place except that a wrench allows you to move it, and in fact to do so while expending much less energy to do so, and the wrench meanwhile (ideally) isn't altered in the process.

Catalysts are fairly specific and limited in terms of what chemical reactions they have an effect on. The means by which catalysts speed up chemical reactions is by lowering what is known as activation energy, that is, the energy required to form the intermediate state between reactants and products.

Figure legend: Diagrammatic representation of the action of a catalyst, shown in low resolution. In the presence of a catalyst, under a given set of reaction conditions, the reactant is rapidly converted to product (top). Absent the catalyst under the same conditions little or no reactant is converted to product (bottom). This allows a control of what chemical reactions occur, what chemical reactions can occur, and when those chemical reactions will occur.

Most biological catalysts are proteins, called enzymes. See, though, also ribozyme.

The following video considers catalysts particularly from a perspective of applied chemistry but with biological emphasis as well:

The following video talks about catalysts within the context of experimental analysis of enzymatic action: