Question 1

Which structural feature distinguishes Gram-positive bacteria from Gram-negative bacteria, as shown in the diagram?

Accepted Answer

Presence of a thick peptidoglycan layer without an outer membrane

Question 2

Based on the diagram, which component is unique to Gram-negative bacteria and not found in Gram-positive bacteria?

Accepted Answer

Outer membrane

Question 3

If a bacterial cell wall is composed of a thick peptidoglycan layer and lacks an outer membrane, how will it appear after Gram staining?

Accepted Answer

Purple, due to retention of crystal violet stain

Question 4

Which of the following best explains why Gram-negative bacteria are generally more resistant to antibiotics that target peptidoglycan synthesis?

Accepted Answer

The outer membrane acts as a barrier to many antibiotics

Question 5

A scientist is studying a bacterium with the following features: a thin peptidoglycan layer, an outer membrane, and porins. According to the diagram and your knowledge, which type of bacterium is this?

Accepted Answer

Gram-negative bacterium

Question 6

Which of the following equations best represents the relationship between the thickness of the peptidoglycan layer ($$t_{PG}) $$and the ability to retain crystal violet stain ($$S_{CV}) in $$Gram staining?

Accepted Answer

$$S_{CV} \propto t_{PG}$$

Question 7

Which of the following statements about the cell wall structure of Gram-positive and Gram-negative bacteria is correct?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane

Question 8

During an experiment, a student observes that a bacterial sample does not retain the crystal violet stain but takes up the counterstain, appearing pink under the microscope. Based on the diagram, what is the most likely explanation?

Accepted Answer

The bacteria have a thin peptidoglycan layer and an outer membrane

Question 9

Which of the following is a function of the outer membrane in Gram-negative bacteria, as illustrated in the diagram?

Accepted Answer

Acts as a selective barrier and contains porins for molecule transport

Question 10

A new antibiotic targets the synthesis of peptidoglycan. Based on the diagram, which type of bacteria would be most susceptible to this antibiotic and why?

Accepted Answer

Gram-positive bacteria, because they have a thick, exposed peptidoglycan layer

Prokaryotes: Bacteria, Archaea, and Eukaryotes – Structure, Function, and Pathogenicity

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