Instead they make protein catalysts called enzymes that provide surfaces on which reactants encounter one another in the proper orientation, and the enzymes may even weaken bonds that are to be broken.
Enzyme function depends on the environment in which the reaction is occurring.
Such factors as temperature and pH can influence greatly the ability of an enzyme to do its job. The following series of experiments illustrates the principles of enzymatically catalyzed reactions in biological systems. The substrates of catecholase are catechol and oxygen . The substrates react with one another within the active site of the enzyme. This is called the fruit browning reaction.