Practice Questions

A particular enzyme mechanism involves a histidine residue that first donates a proton and later accepts a proton. This histidine acts as a

A. Nucleophilic catalyst
B. General acid base catalyst
C. Metal ion coordinator
D. Hydrophobic anchor
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Jul 11, 2026

In the context of enzyme mechanism, the term “ground state destabilization” refers to the concept that the enzyme

A. Destabilizes the substrate through desolvation, strain, or distortion, raising its energy closer to the transition state
B. Permanently alters the substrate to make it more reactive
C. Destabilizes its own structure by removing metal ions
D. Operates most efficiently only in the cellular ground state
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Jul 11, 2026

In the induced fit model, substrate binding triggers a conformational change that

A. Activates proofreading ability
B. Seals the active site and positions catalytic residues correctly
C. Causes cofactor release
D. Permanently denatures other enzyme molecules
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Jul 11, 2026

The involvement of an enzyme in a reaction means the reaction pathway will have

A. More intermediate steps with lower activation energy barriers
B. Fewer intermediate steps
C. A single step without a transition state
D. Higher activation energy
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Jul 11, 2026

An enzyme fully saturated with substrate is operating at Vmax. At this stage, the rate limiting step is most likely

A. Initial substrate binding
B. Diffusion of enzyme and substrate
C. Chemical conversion of substrate into product
D. Product release
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Jul 11, 2026

The concept of electrostatic catalysis involves active site residues

A. Forming transient covalent bonds
B. Using charged side chains to stabilize charge in the transition state
C. Creating a completely non polar environment
D. Mechanically unfolding the substrate
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Jul 11, 2026

The proximity effect in enzyme catalysis refers to the enzyme’s ability to

A. Attract substrates from distant cells
B. Bind substrates close together and in the correct orientation
C. Generate a new substrate molecule
D. Increase proximity to regulatory molecules
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Jul 11, 2026

The formation of a transient acyl enzyme intermediate during chymotrypsin catalysis is an example of

A. Acid base catalysis
B. Electrostatic catalysis
C. Covalent catalysis
D. Metal ion catalysis
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Jul 11, 2026

In the catalytic mechanism of serine proteases, the role of the histidine residue in the catalytic triad is to function as a

A. Strong nucleophile
B. Binding site for hydrophobic side chains
C. General base catalyst
D. Metal chelating ligand
nmdcat.online BIO NMDCAT
Jul 11, 2026

The mechanism by which the active site of an enzyme lowers the activation energy does NOT include

A. Providing a microenvironment different from the bulk aqueous solution
B. Orienting the substrates precisely for a reaction
C. Increasing the local concentration of substrates
D. Permanently increasing the average kinetic energy of the substrate population
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Jul 11, 2026
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