MCAT Physical : Enzymes
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Example Questions
Example Question #1 : Classifications Of Enzymes
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?
Lyase
Ligase
Transferase
Hydrolase
Hydrolase
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?
Suicide inhibitor
Noncompetitive inhibitor
Mixed inhibitor
Competitive inhibitor
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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