Final answer:
Competitive inhibition alters the initial reaction rate and Km value by competing with the substrate for the enzyme's active site; however, it does not change the maximum rate, which can still be reached by increasing substrate concentration. Noncompetitive inhibitors decrease the Vmax by binding elsewhere on the enzyme and disrupting its function regardless of the substrate concentration.
Step-by-step explanation:
Competitive inhibition affects the rate equation by altering the initial rate of the enzyme-catalyzed reactions. A competitive inhibitor competes with the substrate for the active site of the enzyme. Because of this competition, at lower substrate concentrations, the inhibitor can occupy the active site, thus preventing substrate binding and decreasing the reaction rate.
However, the principle of competitive inhibition allows for the possibility that, if the substrate concentration is sufficiently increased, it can outcompete the inhibitor for the active site. In such cases, the normal maximum rate (Vmax) of the reaction can be achieved. Therefore, competitive inhibitors affect the Km value (substrate concentration at which the reaction rate is half of the Vmax), requiring a greater substrate concentration to reach half of the Vmax, but they do not change the Vmax itself.
On the other hand, noncompetitive inhibitors do not compete with the substrate for the active site, as they bind to a different part of the enzyme. Therefore, even if the substrate concentration is increased, noncompetitive inhibitors decrease the Vmax of the reaction because they alter the enzyme's function regardless of the substrate concentration.