ENZYME FUNCTION AND ACTIVATION ENERGY
Enzymes are protein catalysts that carry out the chemical reactions of metabolism. All chemical reactions require activation energy to break chemical bonds and begin the reaction. The need for activation energy acts as a barrier to the chemical reaction occurring and/or to the speed at which it occurs.

Enzymes lower the barriers that normally prevent chemical reactions from occurring (or slow them down) by decreasing the required activation energy. Thus, in the presence of enzymes, reactions proceed and/or proceed at a faster rate.

Enzyme names end with the -ase suffix, unless they were named prior to adoption of the -ase naming system. Often when enzymes are named, the -ase suffix is added to the substrate name. For example, sucrase is the enzyme that breaks down the substrate sucrose, a disaccharide, into the monosaccharides glucose and fructose.