MCAT Physical : Inhibition and Inhibitors

Study concepts, example questions & explanations for MCAT Physical

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Example Questions

Example Question #1 : Inhibition And Inhibitors

Chymotrypsin is a proteolytic enzyme that is released by the pancreas. Using a water molecule, it cleaves the traget polypeptide and creates the new N and C termini for the newly made fragments.

Suppose an inhibitor interacts with chymotrypsin. If the inhibitor acts by noncovalently binding to chymotrypsin, and only decreases its maximum catalytic rate, what type of inhibitor is being used?

Possible Answers:

Mixed inhibitor

Suicide inhibitor

Noncompetitive inhibitor

Competitive inhibitor 

Correct answer:

Noncompetitive inhibitor


We are told that the inhibitor binds noncovalently, so suicide inhibitors are not an option. Since the inhibitor only affects the catalytic rate of the enzyme, and not the Michaelis constant, we can say that the inhibitor is following a mechanism such as that of a noncompeitive inhibitor.

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