In competitive inhibition, what is the effect of adding more substrate?

• A. Decreases enzyme action
• B. Increases enzyme action
• C. No effect
• D. Irreversibly inhibits

Answer: (B)

In competitive inhibition, the inhibitor and substrate compete for the same active site on the enzyme. When you add more substrate, it becomes more likely that the substrate binds the active site instead of the inhibitor, so the reaction rate increases as substrate concentration rises. The maximum rate (Vmax) is unchanged, but you need a higher substrate amount to reach half of that maximum (apparent Km increases). So, increasing substrate levels can overcome the inhibition and enhance enzyme action toward its uninhibited rate.