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Mode of Enzyme Action

60 questions found

Practice Questions

Donation of a proton from hydronium ion (H?O?) in solution to the substrate is an example of

A. General acid catalysis
B. Specific acid catalysis
C. Covalent catalysis
D. Metal ion catalysis
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Jul 11, 2026

The hydrophobic effect contributes to enzyme catalysis primarily by

A. Dissolving the enzyme in membranes
B. Driving substrate binding into the hydrophobic active site
C. Preventing substrate entry
D. Causing enzyme denaturation
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An enediolate intermediate is most likely stabilized by

A. A hydrophobic pocket
B. A positively charged metal ion or lysine residue
C. A negatively charged aspartate residue
D. A neutral cysteine residue
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In glyceraldehyde 3 phosphate dehydrogenase, the catalytic cysteine is activated by a neighboring

A. Aspartate
B. Histidine
C. Zinc ion
D. Arginine
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Stabilization of a negatively charged tetrahedral intermediate is achieved by the

A. Hydrophobic pocket
B. Oxyanion hole
C. Zinc ion
D. Allosteric site
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Pepsin has an optimum pH of about 2 because

A. Its coenzyme works only at low pH
B. Catalytic residues require a specific protonation state
C. The substrate is active only at pH 2
D. Product inhibition occurs at higher pH
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Stereospecificity in enzyme action means the enzyme can

A. Change its own stereochemistry
B. Produce racemic products
C. Distinguish between optical isomers and act on only one
D. Convert every substrate into its optical isomer
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In aldolase, formation of a Schiff base between lysine and the substrate is an example of

A. Cofactor mediated catalysis
B. Covalent catalysis
C. Metal ion catalysis
D. General acid catalysis
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Vmax of an enzyme catalyzed reaction is reached when

A. The enzyme is denatured
B. Product concentration becomes zero
C. Further increase in substrate concentration fails to increase the reaction rate
D. Km becomes zero
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Observation of a burst phase of rapid product formation followed by a slower steady state phase suggests

A. Random sequential binding
B. Rate limiting formation of a covalent enzyme substrate intermediate
C. Rate limiting release of the first product
D. Slow activation of the free enzyme
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Jul 11, 2026

The active site of an enzyme is usually located in a deep cleft or pocket because it

A. Protects the enzyme from phosphorylation
B. Provides a large flat surface for adsorption
C. Sequesters the substrate from bulk solvent and creates a specialized environment
D. Allows simultaneous binding to DNA and proteins
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A Lineweaver Burk plot supporting a ping pong mechanism shows

A. Lines intersecting on the x axis
B. Parallel lines at varying substrate concentrations
C. A single straight line
D. A sigmoidal curve
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The active site of an enzyme is often described as a “microenvironment.” A key characteristic of this microenvironment is

A. A completely uniform charge distribution
B. A significantly lowered dielectric constant that enhances electrostatic interactions
C. A pH always equal to 7.0
D. An unlimited supply of free water molecules
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Jul 11, 2026

A Bi substrate reaction following a Sequential Ordered mechanism is characterized by

A. Random substrate binding
B. Both substrates bind before any product is released, in a compulsory order
C. Product leaves before all substrates bind
D. Reaction rate is independent of the second substrate
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Jul 11, 2026

An enzyme that catalyzes reactions without any non protein component relies solely on

A. Quaternary structure
B. Amino acid side chains arranged in the active site
C. Alpha helices
D. Signal peptide
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In a multistep enzyme mechanism, the overall reaction rate is determined by the step with the

A. Lowest activation energy
B. Highest activation energy
C. Greatest entropy change
D. Largest number of water molecules
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Jul 11, 2026

In lysozyme, Glu35 remains protonated because its microenvironment is

A. Highly hydrophilic
B. Hydrophobic and non polar
C. Rich in lysine residues
D. Completely neutral
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Jul 11, 2026

A ping pong mechanism refers to a kinetic sequence where

A. Substrate inhibits product
B. One product is released before all substrates bind
C. Cooperative binding occurs
D. Non competitive inhibition occurs
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Jul 11, 2026
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