$$\mathrm{NAG} - \mathrm{NAM} - \text{pentapeptide} \xrightarrow{\text{crosslink}} \mathrm{NAG} - \mathrm{NAM} - \text{tetrapeptide}$$

Question 1

Which of the following is NOT a function of the prokaryotic cell (plasma) membrane?

Accepted Answer

Provides structural rigidity to prevent osmotic lysis

Question 2

Peptidoglycan is a major component of bacterial cell walls. Which two sugars are its primary building blocks?

Accepted Answer

N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

Question 3

Why is the bacterial cell wall a good target for antibiotics such as penicillin?

Accepted Answer

It is not present in animal cells, so drugs targeting it are less toxic to humans

Question 4

Which structural feature distinguishes Gram-positive from Gram-negative bacterial cell walls?

Accepted Answer

Presence of teichoic acids

Question 5

A patient is infected with a Gram-negative bacterium. Which component of the cell wall is most likely responsible for toxic effects during infection?

Accepted Answer

Lipopolysaccharide (LPS), specifically Lipid A

Question 6

Which of the following best describes the Gram stain result for Gram-negative bacteria?

Accepted Answer

Pink due to loss of crystal violet and uptake of safranin

Question 7

Which equation best represents the cross-linking in peptidoglycan of Gram-positive bacteria?

Accepted Answer

$$\mathrm{NAG} - \mathrm{NAM} - 	ext{pentapeptide} \xrightarrow{	ext{crosslink}} \mathrm{NAG} - \mathrm{NAM} - 	ext{tetrapeptide}$$

Question 8

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

Accepted Answer

They contain a variety of specialized polysaccharides and proteins

Question 9

Which external structure allows bacteria to adhere to surfaces and is composed of pilin protein?

Accepted Answer

Pili

Question 10

A bacterium is observed to survive extreme dehydration and heat. Which structure is most likely responsible for this resistance?

Accepted Answer

Endospore

Question 11

Which of the following is TRUE regarding the movement of bacterial flagella?

Accepted Answer

Flagella rotate 360° to propel the cell

Question 12

Which of the following best explains why penicillin is generally more effective against Gram-positive bacteria?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and lack an outer membrane, making peptidoglycan synthesis easier to disrupt

Question 13

Which of the following is a function of the glycocalyx in prokaryotes?

Accepted Answer

Protects against drying out and aids in attachment to surfaces

Question 14

Which of the following structures is found in both Gram-positive and Gram-negative bacteria?

Accepted Answer

Peptidoglycan

Question 15

A researcher stains a bacterial sample and observes pink cells under the microscope. Which of the following is most likely TRUE about these cells?

Accepted Answer

They possess an outer membrane containing LPS

Question 16

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

Accepted Answer

They allow small molecules to diffuse across the outer membrane

Question 17

Which of the following is NOT a characteristic of Mycoplasma species?

Accepted Answer

They contain peptidoglycan

Question 18

Which of the following is a correct summary of the differences between Gram-positive and Gram-negative bacteria?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and teichoic acids; Gram-negative have a thin peptidoglycan layer, LPS, and porins

Question 19

Which external structure is responsible for conjugation in bacteria, allowing the transfer of DNA from one cell to another?

Accepted Answer

Pili (specifically F-pilus)

Question 20

Which of the following best describes the arrangement of peptidoglycan in Gram-negative bacteria?

Accepted Answer

Thin peptidoglycan layer located between the inner and outer membranes

Prokaryotic Cell Structure: Membranes and Cell Walls

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