Question 1

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

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.

Question 2

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

Accepted Answer

Lipid A of lipopolysaccharide (LPS)

Question 3

A bacterium is found to be resistant to lysozyme due to the presence of $$\beta(1\rightarrow3)$$ glycosidic bonds in its cell wall. Which type of organism is this most likely to be?

Accepted Answer

An archaeon with pseudomurein

Question 4

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

Accepted Answer

Facilitating ATP synthesis

Question 5

Which of the following statements about peptidoglycan is TRUE?

Accepted Answer

It consists of glycan chains cross-linked by short peptides.

Question 6

A researcher observes a bacterium with multiple flagella distributed all over its surface. What is the correct term for this flagellar arrangement?

Accepted Answer

Peritrichous

Question 7

Which of the following best explains why Mycoplasma species are resistant to antibiotics that target peptidoglycan synthesis?

Accepted Answer

They lack a cell wall and instead have tough cell membranes.

Question 8

Which of the following is a unique feature of the Gram-negative bacterial envelope that is absent in Gram-positive bacteria?

Accepted Answer

Presence of lipopolysaccharide (LPS) in the outer membrane

Question 9

Which of the following structures is responsible for twitching motility in bacteria?

Accepted Answer

Type IV pili

Question 10

A mutation in a Gram-negative bacterium prevents the formation of Braun’s lipoprotein. Which of the following is the most likely consequence?

Accepted Answer

Weakened attachment between the outer membrane and peptidoglycan

Question 11

Which of the following best describes the energy source that drives the rotation of bacterial flagella?

Accepted Answer

Ion motive force (proton gradient)

Question 12

Which of the following is a function of gas vesicles in prokaryotes?

Accepted Answer

Providing buoyancy to position cells in the water column

Question 13

Which of the following statements about archaeal cell walls is correct?

Accepted Answer

Pseudomurein contains $$\beta(1\rightarrow3)$$ glycosidic bonds and only L-amino acids.

Question 14

Which of the following is a major clinical problem associated with Gram-negative bacterial infections?

Accepted Answer

Endotoxic shock caused by immune detection of lipid A

Question 15

Which of the following is a benefit of inclusions in prokaryotic cells?

Accepted Answer

They allow storage of nutrients and other compounds for later use.

Question 16

Which of the following best describes the role of teichoic acids in Gram-positive bacteria?

Accepted Answer

They provide structural strength to the thick peptidoglycan layer.

Question 17

A patient is infected with a bacterium that is pleomorphic and lacks a cell wall. Which of the following is the most likely genus of the infecting organism?

Accepted Answer

Mycoplasma

Question 18

Which of the following is a distinguishing feature of the S-layer in prokaryotes?

Accepted Answer

It is composed of protein and provides structural support and protection.

Question 19

Which of the following is a correct statement about porins in Gram-negative bacteria?

Accepted Answer

They allow the passage of small molecules through the outer membrane.

Question 20

Which of the following best explains why peptidoglycan is a good target for antibiotics?

Accepted Answer

It is unique to bacteria and absent in human cells.

Lecture 12

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