Question 1

Which of the following best explains why the bacterial cell wall is a major target for antibiotics such as penicillin?

Accepted Answer

The cell wall is unique to bacteria and contains peptidoglycan, which is not found in human cells.

Question 2

A Gram-negative bacterium is exposed to lysozyme, which breaks $\beta$-1,4 glycosidic bonds. What is the most likely outcome?

Accepted Answer

The peptidoglycan layer will be degraded, but the outer membrane will provide some protection.

Question 3

Which structural feature distinguishes the cytoplasmic membrane of Archaea from that of Bacteria?

Accepted Answer

Archaeal membranes contain ether linkages between glycerol and their hydrophobic side chains, while bacterial membranes contain ester linkages.

Question 4

During a Gram stain, a student forgets to add the decolorizer (alcohol). What will be the appearance of Gram-negative bacteria under the microscope?

Accepted Answer

They will appear purple, similar to Gram-positive bacteria.

Question 5

Which of the following best describes the function of teichoic acids in Gram-positive cell walls?

Accepted Answer

They provide structural support and contribute to the negative charge of the cell wall.

Question 6

A patient is diagnosed with septic shock caused by a Gram-negative bacterial infection. Which component of the bacterial cell envelope is primarily responsible for this condition?

Accepted Answer

Lipid A portion of lipopolysaccharide (LPS)

Question 7

Which of the following transport systems in bacteria uses the energy from ATP hydrolysis to move substances across the cytoplasmic membrane?

Accepted Answer

ABC (ATP-Binding Cassette) transporters

Question 8

Which of the following statements about peptidoglycan synthesis is correct?

Accepted Answer

Peptidoglycan is synthesized by linking alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) subunits via $\beta$-1,4 glycosidic bonds, with peptide cross-links providing strength.

Question 9

Which of the following best explains why Mycobacterium species are acid-fast?

Accepted Answer

Their cell walls contain high concentrations of mycolic acids, making them resistant to decolorization by acid alcohol.

Question 10

A researcher is studying a bacterium with a single thick peptidoglycan layer, teichoic acids, and no outer membrane. Which of the following is most likely true about this bacterium?

Accepted Answer

It is Gram-positive and will stain purple in a Gram stain.

Question 11

Which of the following is a key difference between facilitated diffusion and active transport in bacterial membranes?

Accepted Answer

Facilitated diffusion does not require energy input, while active transport requires energy, often from ATP or the proton motive force.

Question 12

Which of the following best describes the role of porins in Gram-negative bacteria?

Accepted Answer

They form channels in the outer membrane that allow the passive diffusion of small molecules.

Question 13

Borrelia burgdorferi, the causative agent of Lyme disease, is unusual among bacteria because:

Accepted Answer

It lacks classical lipopolysaccharide (LPS) in its outer membrane.

Question 14

A bacterial cell is placed in a hypotonic solution. Which structure is primarily responsible for preventing osmotic lysis?

Accepted Answer

The cell wall

Question 15

Which of the following statements about group translocation in bacteria is correct?

Accepted Answer

The transported molecule is chemically modified during passage across the membrane, often using phosphoenolpyruvate as the energy source.

Question 16

Which of the following best explains why Streptococcus pyogenes can cause rheumatic fever after a strep throat infection?

Accepted Answer

Molecular mimicry between the bacterial M protein and host tissues leads to an autoimmune response.

Question 17

Which of the following is a major structural difference between Gram-positive and Gram-negative bacterial cell walls?

Accepted Answer

Gram-negative bacteria have an outer membrane containing lipopolysaccharide, while Gram-positive bacteria do not.

Question 18

A mutation in a bacterial ABC transporter gene is most likely to affect which of the following processes?

Accepted Answer

Import or export of specific solutes using ATP hydrolysis

Question 19

Which of the following best describes the composition of the peptidoglycan layer in bacterial cell walls?

Accepted Answer

Alternating polymers of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by short peptides

Microbial Cell Wall and Membrane: Structure, Function, and Diversity

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