Enzymes - 1

Which of the following amino acid residues would provide a side chain capable of increasing the hydrophobicity of a binding site?

• His

• Lys

• Ile

• Arg

• Ser

Which of the following is TRUE about enzymes?

I. Enzymes typically catalyze reactions at much higher rates than chemical catalyst.

II. Enzymes are often very specific for their substrates.

III. Enzyme activities can often be regulated.

IV. Enzymes typically act under milder conditions of temperature and pH than chemical catalysts.

• I, II, III

• I, II, III, IV

• I, II

• III, IV

• II, III, IV

Which of the following is TRUE regarding cofactors?

• Coenzymes are often separate from the enzyme and do not need recharged.

• Metal ions must be covalently attached to function as a cofactor.

• Cofactor is a broad term used for all enzyme "helpers".

• Prosthetic groups can dissociate readily and be regenerated for use in another enzyme.

• An apoenzyme implies that a cofactor is present.

Enzyme X catalyzes the addition of a hydroxyl group to substrate Y. In the process a metal cofactor is reduced and then reoxidized. What class of enzyme is X?

• oxidoreductase

• hydrolase

• ligase

• isomerase

• lyase

The transition state of an enzyme and substrate reaction

• must always bind the enzyme active site with lower energy than the products.

• is stabilized by enhancing the reverse reaction of E + S→ES.

• is composed of true covalent bonds which decrease its energy.

• is stabilized due to the specificity of the active site for the substrate.

• is stabilized by decreasing the effective concentration.

Which of the following is TRUE regarding transition state?

• The free energy between the transition state and the reactants must be negative.

• The transition state can be stabilized by covalent catalysis.

• The transition state represents the ES complex.

• Transition state analogs bind the substrate not the enzyme.

• All of the above are true.

The enzyme pictured above is shown in two configurations, A (open) and B (closed). Upon binding substrate in the active site, the enzyme converts the structure shown in B. Which of the following is true based on the given information?

• The enzyme requires a high concentration of substrate to function.

• This example exemplifies the “lock-and-key” model.

• This enzyme must require ATP.

• This example exemplifies the of “induced fit” model.

• None of these are true.