Question 1

Where does lysozyme cleave the peptidoglycan substrate composed of repeating NAG and NAM units labeled A-F?

Accepted Answer

Between NAG(C) and NAM(D)

Question 2

According to the Phillips Model, what is the primary mechanism by which lysozyme catalyzes the cleavage of its peptidoglycan substrate?

Accepted Answer

Lysozyme distorts the substrate into a strained conformation, facilitating bond cleavage.

Question 3

What effect does lysozyme have on the free energy of activation ($$\Delta G_{activation}) $$for the cleavage of its substrate?

Accepted Answer

Lysozyme decreases $$\Delta G_{activation}$$, making the reaction faster.

Question 4

Which of the following best describes the role of lysozyme in bacterial cell wall degradation?

Accepted Answer

Lysozyme hydrolyzes the glycosidic bond between NAG and NAM.

Question 5

If the free energy of activation for an uncatalyzed reaction is $$50\ 	ext{kJ/mol}$$ and lysozyme lowers it to $$20\ 	ext{kJ/mol}$$, what is the effect on the reaction rate?

Accepted Answer

The reaction rate increases.

Question 6

Which bond is cleaved by lysozyme in the following substrate: NAG(A)----NAM(B)----NAG(C)----NAM(D)----NAG(E)----NAM(F)?

Accepted Answer

The bond between NAG(C) and NAM(D)

Question 7

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

Accepted Answer

Enzymes lower the activation energy but do not change the overall free energy change ($$\Delta G) of $$the reaction.

Question 8

In the Phillips Model, which amino acid residue is primarily involved in the distortion of the substrate in lysozyme's active site?

Accepted Answer

Glutamate

Question 9

A mutation in lysozyme that prevents substrate distortion would most likely result in:

Accepted Answer

Decreased catalytic activity

Question 10

Which of the following best explains why lysozyme is effective against Gram-positive bacteria?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer accessible to lysozyme.

Question 11

If lysozyme is inhibited, what would be the expected outcome for bacterial cell walls?

Accepted Answer

Cell walls would remain intact and resistant to lysis.

Question 12

Which of the following is a plausible reason for lysozyme's specificity for the NAG-NAM bond?

Accepted Answer

Lysozyme recognizes the spatial arrangement and chemical properties of the NAG-NAM bond.

Question 13

Which of the following best describes the change in the reaction coordinate diagram when lysozyme is present?

Accepted Answer

The peak representing activation energy is lower.

Question 14

If the free energy change ($$\Delta G) $$for a reaction is negative, what does this indicate about the reaction?

Accepted Answer

The reaction is exergonic and spontaneous.

Question 15

Which of the following is NOT a function of lysozyme?

Accepted Answer

Phosphorylating peptidoglycan

Question 16

A patient with a deficiency in lysozyme would be most susceptible to which of the following?

Accepted Answer

Bacterial infections

Question 17

Which of the following best describes the effect of lysozyme on the transition state of its substrate?

Accepted Answer

Lysozyme stabilizes the transition state, lowering the activation energy.

Question 18

Which of the following is a consequence of lysozyme activity in tears and saliva?

Accepted Answer

Protection against bacterial invasion

Question 19

Which of the following is a plausible outcome if lysozyme is mutated to lose its ability to distort the substrate?

Accepted Answer

The enzyme would lose its catalytic activity.

Lysozyme Catalysis and Enzyme Mechanisms Study Guide

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