Question 1

Which of the following statements best describes the role of enzymes in chemical reactions?

Accepted Answer

Enzymes lower the activation energy without changing the overall free energy of the reaction.

Question 2

Papain, a cysteine protease found in papaya, is used in the meat industry for tenderization. What property of papain makes it effective for this application?

Accepted Answer

It breaks down proteins into smaller peptides and amino acids.

Question 3

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

Accepted Answer

A holoenzyme consists of the apoenzyme plus its cofactor, while an apoenzyme is the protein portion alone.

Question 4

Which enzyme classification (EC number) would best describe an enzyme that catalyzes the transfer of a phosphate group from ATP to glucose?

Accepted Answer

Transferase (EC 2)

Question 5

The induced fit model of enzyme action differs from the lock-and-key model in which way?

Accepted Answer

The induced fit model proposes that the enzyme undergoes a conformational change upon substrate binding.

Question 6

Which of the following is an example of enzyme regulation by covalent modification?

Accepted Answer

Phosphorylation of an enzyme by a kinase.

Question 7

A zymogen is best described as:

Accepted Answer

An inactive precursor of an enzyme that requires cleavage for activation.

Question 8

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzymes are highly specific, often catalyzing only one type of chemical reaction and interacting with one or a few substrates.

Question 9

Which of the following is a correct representation of the reaction catalyzed by hexokinase?

Accepted Answer

$$\mathrm{Glucose} + \mathrm{ATP} \longrightarrow \mathrm{glucose	ext{-}6	ext{-}phosphate} + \mathrm{ADP}$$

Question 10

Which of the following mechanisms is an example of negative feedback regulation in metabolic pathways?

Accepted Answer

The end product of a pathway inhibits an early enzyme in the same pathway.

Question 11

Which of the following best explains why enzymes accelerate chemical reactions?

Accepted Answer

They stabilize the transition state, lowering the activation energy required.

Question 12

Which of the following is a property of enzymes that distinguishes them from non-biological catalysts?

Accepted Answer

Enzymes are highly specific for their substrates and reactions.

Question 13

A patient with pancreatitis may suffer from tissue damage due to the premature activation of which type of enzyme?

Accepted Answer

Zymogens such as trypsinogen in the pancreas.

Question 14

Which of the following is NOT a correct description of enzyme nomenclature?

Accepted Answer

Enzymes are named solely based on their amino acid sequence.

Question 15

Which of the following statements about coenzymes is correct?

Accepted Answer

Coenzymes are small organic molecules that assist enzymes in catalysis.

Question 16

Which of the following best describes the effect of increasing substrate concentration on enzyme-catalyzed reaction rates?

Accepted Answer

The reaction rate increases until the enzyme becomes saturated, after which it levels off.

Question 17

Which of the following is a correct statement about the energy profile of an enzyme-catalyzed reaction?

Accepted Answer

The activation energy ($$E_a) is $$lower in the presence of an enzyme.

Question 18

Which of the following is an example of an allosteric effector?

Accepted Answer

A molecule that binds to a site other than the active site and modulates enzyme activity.

Question 19

Which of the following statements about the transition state in enzyme-catalyzed reactions is correct?

Accepted Answer

Enzymes stabilize the transition state, increasing the probability of product formation.

Enzymes: Structure, Function, and Regulation

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