Catalysis

Abstract

Reactions can not only be accelerated by raising their temperatures, but also by addition of small amounts of a substance, a so-called catalyst, which is not consumed during the process. An everyday example of a catalyst is the exhaust gas catalytic converter in motor vehicles with gasoline engines, which eliminates combustion pollutants by accelerating subsequent reactions. But why do reactions proceed faster with a catalyst than without a catalyst? The catalyst lowers the reaction resistance by opening up more easily accessible bypasses with smaller activation thresholds. Enzymes, the vitally essential biological catalysts, and the kinetics of their reactions with structurally suitable substrates are discussed in detail. An enzyme can be compared to a lock into which only the proper key (substrate) can fit (key–lock principle). This is where the “key” for the exceedingly high substrate specificity of an enzyme lies. The chapter ends with the discussion of the technically important heterogeneous catalysis.