Question 1

Which of the following best describes the role of an enzyme in a chemical reaction?

Accepted Answer

An enzyme lowers the activation energy, increasing the reaction rate.

Question 2

A patient is given a drug that inhibits the activity of kinases. Which type of reaction will be most directly affected?

Accepted Answer

Transfer of phosphoryl groups between substrates

Question 3

Which of the following equations correctly represents the general reaction catalyzed by a hydrolase?

Accepted Answer

$$R-COOR' + H_2O \rightarrow R-COOH + R'-OH$$

Question 4

Which enzyme class catalyzes the rearrangement of atoms within a molecule to form an isomer?

Accepted Answer

Isomerases

Question 5

A reaction catalyzed by alcohol dehydrogenase is shown below:

$$CH_3CH_2OH + NAD^+ \rightleftharpoons CH_3CHO + NADH + H^+$$

Which class of enzyme is responsible for this reaction?

Accepted Answer

Oxidoreductase

Question 6

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Highly specific enzymes catalyze a single reaction for a single substrate.

Question 7

Why does the induced fit model more accurately describe enzyme-substrate binding than the lock-and-key model?

Accepted Answer

The induced fit model accounts for conformational changes in the enzyme upon substrate binding.

Question 8

Which of the following factors will NOT increase the rate of an enzyme-catalyzed reaction if the enzyme is already saturated with substrate?

Accepted Answer

Increasing substrate concentration

Question 9

A scientist is studying a reaction that requires ATP hydrolysis to proceed. Which enzyme class is most likely involved?

Accepted Answer

Ligases

Question 10

Which of the following best explains why human trypsin is not active in a thermophilic organism living at 75 $$^\circC$$?

Accepted Answer

The enzyme denatures at high temperatures, losing its functional shape.

Question 11

Which of the following is a correct statement about the effect of enzyme concentration on reaction rate, assuming excess substrate is present?

Accepted Answer

The reaction rate increases linearly with enzyme concentration.

Question 12

A mutation in an enzyme's active site changes a hydrophobic pocket to a hydrophilic one. What is the most likely effect on enzyme activity?

Accepted Answer

The enzyme will lose specificity for hydrophobic substrates.

Question 13

Which of the following best describes the function of a coenzyme in an oxidoreductase-catalyzed reaction?

Accepted Answer

It acts as an electron carrier, being reduced or oxidized during the reaction.

Question 14

Which subclass of hydrolases is responsible for breaking the 1,4 glycosidic bonds in amylose (starch)?

Accepted Answer

Amylases

Question 15

A patient has a deficiency in a vitamin-derived coenzyme required for dehydrogenase activity. Which process will be most directly affected?

Accepted Answer

Oxidation-reduction reactions

Question 16

Which of the following statements about enzyme catalysis is correct?

Accepted Answer

Enzymes are not consumed and can be reused for multiple reactions.

Question 17

Which of the following best describes the effect of pH on enzyme activity?

Accepted Answer

Each enzyme has an optimal pH at which its activity is maximal.

Question 18

A scientist observes that increasing substrate concentration increases reaction rate, but only up to a certain point. What is the most likely explanation?

Accepted Answer

The enzyme becomes saturated with substrate, and the rate reaches a maximum.

Question 19

Which of the following is a correct example of a transferase-catalyzed reaction?

Accepted Answer

$$Fructose\ 6$$-$$phosphate + ATP \rightarrow Fructose\ 1,6$$-$$bisphosphate + ADP$$

Question 20

Which of the following best describes the difference between a cofactor and a coenzyme?

Accepted Answer

A cofactor is an inorganic ion, while a coenzyme is an organic molecule.

Enzyme Classification, Mechanisms, and Regulation: GOB Chemistry Study Guide

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