Final answer:
Enzymes significantly quicken chemical reactions by reducing the required activation energy, which leads to an increase in the reaction rate without affecting the overall free energy change or the stability and efficiency of the reaction. Option B is correct.
Step-by-step explanation:
How does the reduction in activation energy by an enzyme affect a chemical reaction? The main effect of this reduction is that the reaction proceeds at a faster rate (Option B). This is because enzymes act as catalysts and lower the activation energy necessary to start a chemical reaction. Activation energy is the initial energy required to break chemical bonds in the reactants so they can form new ones and produce the reaction's products.
Enzymes achieve this by binding to the reactant molecules, or substrates, and holding them in a way that reduces the amount of energy needed for the reactants to collide with each other and react. Despite this lowered activation energy, the overall free energy change of the reaction remains unchanged, indicating that the presence of an enzyme does not affect the stability of the products or the efficiency of the reaction itself.