Final answer:
Enzymes lower the activation energy of reactions rather than increasing the energy of reactants, making the statement false. They act as catalysts to facilitate reactions by binding to substrates.
Step-by-step explanation:
Enzymes do not increase the average energy of reactant molecules; rather, they function by lowering the activation energy required for a reaction to occur. This is accomplished by the enzyme binding to the reactant molecules, or substrates, and holding them in such a way that the chemical bond-breaking and bond-forming processes occur more readily. Consequently, enzymes accelerate reactions by making it easier for substrates to reach the transition state, but they do not affect the overall free energy change (ΔG) of the reaction and do not make endergonic reactions exergonic.
In summary, the statement 'Enzymes increase the average energy of reactant molecules' is false. They are organic catalysts that specifically bind to substrates to facilitate chemical reactions without altering the innate energy levels of the reactants or products involved.