Question 1

Which of the following best describes the main structural difference between Gram-positive and Gram-negative bacterial cell envelopes, as shown in the provided diagrams?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides.

Question 2

A patient develops a severe infection after a burn injury. The causative agent is a Gram-negative bacterium that forms capsules and is resistant to many antibiotics. Which virulence factor most likely contributes to its resistance to antibiotics?

Accepted Answer

The presence of an outer membrane containing lipopolysaccharides (LPS), which acts as a barrier to many antibiotics.

Question 3

Which component of the Gram-negative outer membrane is responsible for triggering septic shock in humans?

Accepted Answer

Lipid A portion of lipopolysaccharide (LPS)

Question 4

A bacterium is observed to survive boiling water, desiccation, and exposure to UV light. Which structure is most likely responsible for this extreme resistance?

Accepted Answer

Endospore

Question 5

Which of the following best explains why antibiotics targeting peptidoglycan synthesis are ineffective against Mycoplasma pneumoniae?

Accepted Answer

Mycoplasma pneumoniae lacks a cell wall and therefore does not contain peptidoglycan.

Question 6

Which of the following is a correct description of horizontal gene transfer by conjugation in bacteria?

Accepted Answer

A donor cell forms a pilus to transfer a plasmid to a recipient cell, resulting in both cells possessing the plasmid.

Question 7

Which of the following best describes the function of bacterial ribosomes?

Accepted Answer

They synthesize proteins using mRNA as a template.

Question 8

A patient is diagnosed with tetanus after a puncture wound. Which two bacterial features are most responsible for the disease symptoms?

Accepted Answer

Endospore formation and exotoxin production by Clostridium tetani

Question 9

Which of the following best explains why biofilms are difficult to eradicate from medical devices?

Accepted Answer

The glycocalyx matrix protects microbes from immune responses, heat, chemicals, and mechanical removal.

Question 10

Which of the following is a distinguishing feature of acid-fast bacteria such as Mycobacterium tuberculosis?

Accepted Answer

A waxy mycolic acid layer outside the peptidoglycan, making them resistant to dyes and many antibiotics.

Question 11

Which of the following best describes the role of plasmids in bacterial cells?

Accepted Answer

Plasmids are small, independently replicating DNA molecules that often carry genes for antibiotic resistance or toxin production.

Question 12

Which of the following is a correct statement about the movement of bacteria with peritrichous flagella?

Accepted Answer

They move by a series of runs and tumbles, changing direction in response to environmental signals.

Question 13

Which of the following is NOT a function of a bacterial capsule?

Accepted Answer

Facilitating protein synthesis

Question 14

Which of the following best explains why Clostridium botulinum is a major concern in improperly canned foods?

Accepted Answer

Its endospores can survive canning and germinate in anaerobic conditions, producing a potent neurotoxin.

Question 15

Which of the following statements about Archaea is correct?

Accepted Answer

Archaea are more closely related to Eukarya than to Bacteria based on ribosomal RNA sequences.

Question 16

Which of the following is a correct pairing of a bacterial structure and its primary function?

Accepted Answer

Fimbriae – attachment to surfaces

Question 17

A patient with recurrent Clostridioides difficile infection is successfully treated with a fecal microbiota transplant (FMT). What is the main reason this treatment is effective?

Accepted Answer

FMT restores mutualistic bacteria that outcompete C. difficile in the gut microbiome.

Question 18

Which of the following best describes the structure of peptidoglycan?

Accepted Answer

Long chains of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross-linked by peptide bridges.

Question 19

Which of the following is the most potent bacterial toxin based on LD50 values?

Accepted Answer

Botulinum toxin

Functional Anatomy of Prokaryotic Cells: Structure, Classification, and Virulence

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