Question 1

Which of the following best describes the main structural difference between gram-positive and gram-negative bacterial cell walls?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and one membrane, while gram-negative bacteria have a thin peptidoglycan layer and two membranes.

Question 2

What is the primary function of the bacterial cell wall?

Accepted Answer

To prevent cell lysis due to osmotic pressure.

Question 3

Which component is unique to the cell wall of gram-negative bacteria and acts as an additional barrier against harmful agents?

Accepted Answer

Lipopolysaccharide (LPS)

Question 4

Which enzyme cleaves the bonds between N-acetylglucosamine and N-acetylmuramic acid in peptidoglycan?

Accepted Answer

Lysozyme

Question 5

What is the toxic component of lipopolysaccharide (LPS) found in gram-negative bacteria?

Accepted Answer

Lipid A

Question 6

Which of the following statements about peptidoglycan is TRUE?

Accepted Answer

It is composed of alternating repeats of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) in $$\beta-1$$,4 linkages.

Question 7

Which type of bond connects the glycan backbone in archaeal pseudomurein?

Accepted Answer

$$\beta-1$$,3 glycosidic bond

Question 8

A patient is infected with a bacterium that is resistant to lysozyme and penicillin. Which cell wall structure is most likely present?

Accepted Answer

Pseudomurein

Question 9

Which of the following is a function of teichoic acids in gram-positive bacteria?

Accepted Answer

They bind $$\mathrm{Ca$$^{2+}$$}$$ and $$\mathrm{Mg$$^{2+}$$}$$ prior to transport.

Question 10

Which structure is always the outermost layer in archaeal cell walls and allows small molecules to pass through while excluding large molecules?

Accepted Answer

S-layer

Question 11

Which of the following best explains why Mycoplasma can survive without a cell wall?

Accepted Answer

They contain sterols or lipoglycans in their membranes for added strength.

Question 12

Which of the following is NOT a component of the peptidoglycan structure in bacteria?

Accepted Answer

Lipid A

Question 13

What is the role of porins in gram-negative bacteria?

Accepted Answer

They act as channels for solutes to cross the outer membrane.

Question 14

Which of the following statements about the periplasmic space in gram-negative bacteria is correct?

Accepted Answer

It contains hydrolytic enzymes, binding proteins, and chemoreceptors.

Question 15

Which of the following antibiotics targets the crosslinking of peptidoglycan chains?

Accepted Answer

Penicillin

Question 16

A researcher isolates a prokaryote with a cell wall composed of interlocking protein molecules forming a hexagonal symmetry. Which cell wall type is most likely present?

Accepted Answer

S-layer

Question 17

Which of the following is TRUE regarding the amino acids in archaeal pseudomurein?

Accepted Answer

All amino acids are the L-stereoisomer.

Question 18

Which of the following statements about the glycan portion of peptidoglycan is correct?

Accepted Answer

It is composed of alternating NAG and NAM residues.

Question 19

Which of the following is a correct description of the function of Braun lipoprotein in gram-negative bacteria?

Accepted Answer

It attaches the outer membrane to the peptidoglycan layer.

Question 20

Which of the following is a reason why S-layer is considered sufficiently strong to withstand osmotic lysis in some Archaea?

Accepted Answer

It consists of interlocking protein or glycoprotein molecules forming a paracrystalline structure.

Bacterial and Archaeal Cell Wall Structures: Comparative Analysis and Functional Differences

Study Guide - Practice Questions

Study Guide - Flashcards