Final answer:
When non-competitive inhibition occurs, the maximum reaction rate (V max) decreases, while the affinity of the enzyme for the substrate, reflected by the Michaelis constant (Km), remains unchanged.
Step-by-step explanation:
When non-competitive inhibition occurs, Vmax decreases but Km stays the same. Non-competitive inhibitors can bind to either the enzyme alone or the enzyme-substrate complex, as their binding site is different from the active site. This binding changes the enzyme's shape, affecting the reaction rate. Even when more substrate is added, the maximal rate of the enzyme activity cannot be reached, indicating that Vmax is reduced but Km is unaffected.
In comparison, competitive inhibition is characterized by the inhibitor competing with the substrate for the enzyme active site. It affects the reaction rate initially but does not alter Vmax since increasing substrate concentration can overcome this type of inhibition. Uncompetitive and mixed inhibition also differ from non-competitive inhibition in terms of their effects on Vmax and Km.