Enzymes are named on the basis of the reactions they catalyze. For example, amylase is the enzyme which helps to digest amylose, a type of starch. The shape of the active site may be molded to fit the surface characteristics of the substrate molecule. Substrates may also be covalently bonded to enzymes. Enzymes work by reducing the activation energy of the reaction.
Activation energy is the initial input of energy required to get the reaction started.
Once this reduction in activation energy is completed, the reactants more easily surmount the energy barrier, at which point the reaction may proceed spontaneously with the release of free energy. Within cells a number of phenomena regulate enzyme function. In some cases, irreversible inhibition may occur. Often, reversible inhibition occurs by either of two methods, competitive and noncompetitive inhibition. The latter occurs as a result of involvement of the allosteric site of the enzyme.