A catalyst in chemistry or biology is a substance that accelerates the rate of a chemical reaction but is unconsumed by the reaction. A catalyst participates in the reaction but is neither a chemical reactant nor a chemical product. Catalysts enable reactions to occur much faster or at lower temperatures because of changes that they induce in the reactants.
Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process regenerating the catalyst.
Catalysts work by providing an (alternative) mechanism involving a different transition state and lower activation energy. The catalyst stabilizes the transition state more than it stabilizes the starting material. It decreases the kinetic barrier by decreasing the difference in energy between starting material and transition state.
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