Enzymes are called biocatalysts because they function in chemical reactions that involve living organisms [biologial organisms]. Enzymes generally increase the rate of metabolic reactions by lowering the activation energy, making it easier for the reaction to occur easily and rapidly. Without enzymes, some metabolic reactions may take a very long time before they are completed. Enzymes used in laboratory chemical reactions are not biocatalysts because they are not catalysing reactions in biological organisms.