Competitive and noncompetitive inhibition Knowledge-Based Practice

Questions

1. 1.

   Which feature is shared by both classic competitive and noncompetitive enzyme inhibition?

   • A) Both types of inhibitors can have their effects fully overcome by adding excess substrate.
   • B) Both types of inhibitors share a close structural resemblance to the natural substrate.
   • C) Both types of inhibitors bind to the enzyme through non-covalent, reversible interactions.
   • D) Both types of inhibitors bind directly within the catalytic active site of the enzyme.
2. 2.

   Which molecular complex can form during reversible noncompetitive inhibition, but cannot form during competitive inhibition?

   • A) Free enzyme-inhibitor (EI) complex
   • B) Enzyme-substrate (ES) complex
   • C) Enzyme-substrate-inhibitor (ESI) complex
   • D) Enzyme-product (EP) complex
3. 3.

   In enzyme kinetics, how do competitive and noncompetitive inhibitors distinctively alter the kinetic parameters $V_{\max}$ (maximum velocity) and $K_m$ (Michaelis constant) of a reaction?

   • A) Competitive inhibitors decrease $V_{\max}$ and leave $K_m$ unchanged, whereas noncompetitive inhibitors increase $K_m$ and leave $V_{\max}$ unchanged.
   • B) Competitive inhibitors decrease both $V_{\max}$ and $K_m$, whereas noncompetitive inhibitors decrease $V_{\max}$ but increase $K_m$.
   • C) Competitive inhibitors increase the apparent $K_m$ without altering $V_{\max}$, whereas noncompetitive inhibitors decrease $V_{\max}$ without altering the apparent $K_m$.
   • D) Competitive inhibitors leave both $V_{\max}$ and $K_m$ unchanged, whereas noncompetitive inhibitors decrease both $V_{\max}$ and $K_m$.
4. 4.

   Which statement correctly describes how competitive and noncompetitive inhibitors differ in their binding location and structural resemblance to the natural substrate?

   • A) Competitive inhibitors bind to an allosteric site and mimic the substrate, whereas noncompetitive inhibitors bind directly to the active site.
   • B) Competitive inhibitors structurally resemble the substrate and bind to the active site, whereas noncompetitive inhibitors bind to an allosteric site without mimicking the substrate.
   • C) Competitive inhibitors bind to regulatory regions away from the catalytic center, whereas noncompetitive inhibitors must share the exact shape of the substrate.
   • D) Competitive inhibitors form permanent covalent bonds with non-catalytic residues, whereas noncompetitive inhibitors compete reversibly for the catalytic pocket.
5. 5.

   How does increasing the substrate concentration affect an enzyme-catalyzed reaction experiencing competitive inhibition compared to one experiencing noncompetitive inhibition?

   • A) It decreases the maximum reaction rate in competitive inhibition but has no effect on noncompetitive inhibition.
   • B) It can overcome competitive inhibition by outcompeting the inhibitor, but it cannot overcome noncompetitive inhibition.
   • C) It permanently alters the allosteric site in competitive inhibition while leaving the active site unchanged in noncompetitive inhibition.
   • D) It restores the reaction rate in noncompetitive inhibition by displacing the inhibitor from the active site, but it fails in competitive inhibition.

Answers and step-by-step solutions appear after you finish the test.