Question 1

Which of the following best describes the primary function of an enzyme in a biological system?

Accepted Answer

An enzyme decreases the activation energy required for a reaction to proceed.

Question 2

A patient presents with elevated serum lipase and amylase. Both enzymes are classified as hydrolases. What type of reaction do hydrolases catalyze?

Accepted Answer

Cleavage of bonds using water (hydrolysis)

Question 3

Which of the following statements about enzyme cofactors is CORRECT?

Accepted Answer

Cofactors can be either organic molecules (coenzymes) or inorganic ions.

Question 4

Which enzyme classification is responsible for catalyzing the transfer of an amino group from one molecule to another?

Accepted Answer

Transferases

Question 5

Which model of enzyme-substrate interaction explains how some enzymes can act on a wide range of substrates with similar shapes?

Accepted Answer

Induced-fit model

Question 6

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Competing with the substrate for binding at the active site due to structural similarity.

Question 7

Which of the following best describes a zymogen (proenzyme)?

Accepted Answer

An inactive precursor that is activated by cleavage when needed.

Question 8

Why is it important for digestive enzymes like pepsin and trypsin to be produced as zymogens?

Accepted Answer

To ensure they are only active when and where needed, preventing damage to tissues.

Question 9

Which of the following scenarios describes negative allosteric control of an enzyme?

Accepted Answer

A regulator binds to the enzyme and decreases the ability of the active site to bind substrate.

Question 10

A patient with a gallstone blocking the ampulla of Vater develops pancreatitis. Which of the following best explains why the pancreas begins to digest itself?

Accepted Answer

Trypsinogen is activated prematurely inside the pancreas, leading to activation of other zymogens.

Question 11

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

Accepted Answer

Enzyme activity increases with temperature up to an optimum, then rapidly decreases due to denaturation.

Question 12

Which of the following is an example of an irreversible enzyme inhibitor?

Accepted Answer

Penicillin binding covalently to bacterial transpeptidase.

Question 13

Which of the following equations correctly represents the hydrolysis of a triacylglycerol by lipase?

Accepted Answer

$$\mathrm{Triacylglycerol} + 3\ H_2O \xrightarrow{	ext{lipase}} \mathrm{Glycerol} + 3\ \mathrm{Fatty\ acids}$$

Question 14

Which of the following best describes the role of enteropeptidase in the digestive system?

Accepted Answer

It hydrolyzes a specific peptide bond in trypsinogen, activating it to trypsin.

Question 15

Which of the following is a correct statement about the effect of pH on enzyme activity?

Accepted Answer

Enzyme activity is highest at the optimum pH and decreases at pH values above or below this optimum.

Question 16

Which of the following is NOT a function of proteins in the body?

Accepted Answer

Storage of genetic information

Question 17

A patient is treated for methanol poisoning with ethanol. Why is ethanol effective in this scenario?

Accepted Answer

Ethanol acts as a competitive inhibitor with respect to methanol for alcohol dehydrogenase, reducing the formation of toxic formaldehyde.

Question 18

Which of the following best describes the difference between a holoenzyme and an apoenzyme?

Accepted Answer

A holoenzyme is the active enzyme with its cofactor, while an apoenzyme is the inactive protein portion alone.

Question 19

Which of the following is a real-life application of measuring enzyme levels in clinical diagnosis?

Accepted Answer

Diagnosing a heart attack by measuring serum troponin and creatine kinase levels.

Enzymes: Structure, Function, and Clinical Relevance

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