How does competitive inhibition affect Vmax?

In the context of competitive inhibition, Vmax remains unchanged. This is due to the nature of competitive inhibitors, which compete with the substrate for binding to the active site of the enzyme. When a competitive inhibitor is present, it does not affect the maximum rate of the reaction (Vmax) that can be achieved when the substrate concentration is sufficiently high.

In competitive inhibition, increasing the concentration of the substrate can overcome the effect of the inhibitor, allowing the enzyme to reach its maximum reaction rate as if the inhibitor were not present. Therefore, while the presence of a competitive inhibitor affects the apparent affinity of the enzyme for the substrate (reflected in an increased Km), it does not alter the maximum capacity (Vmax) that can be reached when the enzyme is fully saturated with substrate.

In summary, the correct answer reflects the unchanged Vmax in competitive inhibition, indicating that the inhibitor only affects the enzyme's activity at lower substrate concentrations and does not inhibit the maximum reaction velocity.