Final answer:
Noncompetitive inhibition differs from competitive inhibition as it involves an inhibitor binding to an allosteric site, not competing with the substrate, and alters the maximal reaction rate. Competitive inhibitors bind to the active site and compete with the substrate, but their effect can be overcome by increasing substrate concentration.
Step-by-step explanation:
Noncompetitive inhibition and competitive inhibition are two ways in which enzymes can be regulated and their activity modulated, yet they function differently. In competitive inhibition, an inhibitor competes directly with the substrate for binding to the active site of the enzyme. The inhibitor resembles the substrate's structure, enabling it to fit the active site, but it prevents the enzyme from catalyzing a reaction. However, this type of inhibition is reversible and can be overcome by increasing the substrate concentration, reaching the normal maximum reaction rate once enough substrate displaces the inhibitor. In contrast, noncompetitive inhibition involves an inhibitor binding to an allosteric site on the enzyme, not the active site, which leads to the alteration of the enzyme's shape and therefore its function. As it does not compete with the substrate for the active site, the addition of more substrate does not reverse the inhibition, thus affecting the maximal reaction rate. The primary difference is that competitive inhibitors affect the initial rate but not the maximal rate of reaction, whereas noncompetitive inhibitors decrease the maximal rate regardless of substrate concentration.