Final answer:
Enzymes lower the activation energy for chemical reactions, which allows processes that would otherwise be too slow or unfavorable to occur quickly enough to sustain life, without changing the overall free energy of the reactants or products.
Step-by-step explanation:
Enzymes facilitate unfavorable reactions by lowering the activation energy required for these reactions to proceed. They do this by binding to substrate molecules in the active site, aligning them in such a way that promotes more efficient chemical bond-breaking and bond-forming. This process enhances reaction rates without altering the overall free energy (ΔG) of the reactants or products, merely making it easier for the transition state to be achieved. An example that illustrates the importance of enzymes is Sanfilippo Syndrome type B, a condition where the lack of a specific enzyme to break down mucopolysaccharides leads to progressive brain damage because waste products accumulate in cells, indicating that without enzymatic activity, essential bodily functions cannot proceed effectively.