Enzymes are used up as a part of the reaction and cannot be used again. Enzymes can be any shape to bind to the substrate. Enzymes are catalysts that lower the activation energy allowing the reaction to occur. Enzymes are formed into lipids. 3. Which macromolecule is most likely to be broken down for quick energy? nucleic acid carbohydrate phospholipid protein The Central Role of Enzymes as Biological Catalysts. A fundamental task of proteins is to act as enzymes—catalysts that increase the rate of virtually all the chemical reactions within cells. Although RNAs are capable of catalyzing some reactions, most biological reactions are catalyzed by proteins.