MCAT Physical : Enzymes

Study concepts, example questions & explanations for MCAT Physical

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Example Questions

Example Question #194 : Biochemistry, Organic Chemistry, And Other Concepts

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.

Based on this enzymatic function, what type of enzyme is chymotrypsin?

Possible Answers:

Ligase

Transferase

Lyase

Hydrolase

Correct answer:

Hydrolase

Explanation:

Chymostrypsin creates smaller peptide segments, so it is not a ligase or transferase. Since it employs the use of a water molecule in order to cleave the polymer, it is classified as a hydrolase enzyme. Lyases also shorten polymers, but not with the use of a water molecule.

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:

Suicide inhibitor

Mixed inhibitor

Noncompetitive inhibitor

Competitive inhibitor 

Correct answer:

Noncompetitive inhibitor

Explanation:

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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