Final answer:
Enzymes, a class of protein, lower the energy of activation during a reaction by binding to reactant molecules and facilitating the formation and breaking of chemical bonds. This lowers the energy barrier and increases the reaction rate.
Step-by-step explanation:
An enzyme is a class of protein that primarily functions by lowering the energy of activation during a reaction. Activation energy is the energy required to form or break chemical bonds and convert reactants to products. Enzymes achieve this by binding to the reactant molecules and holding them in such a way that speeds up the reaction, reducing the energy barrier.