The objective of this lab is to familiarize you with biological catalysts enzymes and their activity. 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. Enzymes carry out their function of lowering activation energy by temporarily combining with the chemicals involved in the reaction. Enzymes are specific for their substrate: a particular substrate molecule will combine temporarily with one enzyme type, and the active site of a particular enzyme will fit only one kind of substrate.