Catalysis

Catalysis is the speeding up of a chemical reaction by a substance, called a catalyst, that is not used up in the process. A catalyst provides an alternative route with a lower activation energy, so the reaction runs faster without changing the energy difference between reactants and products.

A catalyst forms temporary bonds with the reactants, stabilizes the unstable transition state and then releases the products. Because it does not change the overall Gibbs free energy of the reaction, it cannot make an unfavorable reaction proceed, and it speeds the forward and reverse reactions equally. The term was introduced by the chemist Jöns Jacob Berzelius in 1835, and Wilhelm Ostwald received the 1909 Nobel Prize in Chemistry for his work on it.

Enzymes are protein catalysts that bring reactants together in an active site in the right orientation, and they can raise rates by factors of a million or more. Catalase, which breaks down hydrogen peroxide, can process millions of molecules per second per enzyme. Some RNA molecules, called ribozymes, are also catalysts, which supports the RNA world hypothesis.

Industrial processes such as the Haber-Bosch process, which uses an iron catalyst to make ammonia for fertilizer, depend on catalysts, as do the converters that clean the exhaust of cars. Researchers engineer enzymes in biotechnology, including those from extremophiles that work at high temperatures. The regulation of catalysts in cells is described in allosteric regulation.

• Enzymes — biological catalysts
• Activation Energy — the barrier a catalyst lowers
• Haber-Bosch Process — an industrial catalytic process