Enzymes lower the activation energy required for a chemical reaction to take place by providing an alternative pathway for the reaction. This is achieved through the formation of an enzyme-substrate complex, which brings the reactants into close proximity and aligns them in an optimal orientation for the reaction to occur. Additionally, enzymes can stabilize the transition state of the reaction, which is the high-energy intermediate state that forms during the reaction. By lowering the activation energy, enzymes increase the rate of the reaction without being consumed in the process, acting as catalysts for the reaction.