Which statement best describes competitive inhibitors?

Which statement best describes competitive inhibitors?

• A. They increase substrate turnover
• B. They block substrate from binding by occupying the active site
• C. They do not affect the enzyme
• D. They stabilize the enzyme-substrate complex

Answer: (B)

Competitive inhibitors work by binding to the enzyme’s active site, competing directly with the substrate for that spot. That means they block substrate binding simply by occupying the same site the substrate would use, which is exactly what the statement describes. Because the inhibitor and substrate compete for the same site, the presence of the inhibitor makes it look like the enzyme has a lower affinity for the substrate (apparent Km increases), but the maximum rate (Vmax) is still achievable if you flood the system with enough substrate. This type of inhibition can be overcome by high substrate concentration, since the substrate can outcompete the inhibitor for the active site. The other choices don’t fit: competitive inhibitors don’t increase turnover; they do affect the enzyme by preventing substrate binding; and they don’t stabilize the enzyme–substrate complex—in fact, they prevent it from forming.

Competitive inhibitors work by binding to the enzyme’s active site, competing directly with the substrate for that spot. That means they block substrate binding simply by occupying the same site the substrate would use, which is exactly what the statement describes. Because the inhibitor and substrate compete for the same site, the presence of the inhibitor makes it look like the enzyme has a lower affinity for the substrate (apparent Km increases), but the maximum rate (Vmax) is still achievable if you flood the system with enough substrate. This type of inhibition can be overcome by high substrate concentration, since the substrate can outcompete the inhibitor for the active site. The other choices don’t fit: competitive inhibitors don’t increase turnover; they do affect the enzyme by preventing substrate binding; and they don’t stabilize the enzyme–substrate complex—in fact, they prevent it from forming.