Question 1

Which of the following best explains why Gram-negative bacteria are more resistant to certain antibiotics than Gram-positive bacteria?

Accepted Answer

Their outer membrane acts as a selective barrier, limiting antibiotic penetration.

Question 2

A patient sample is stained using the Ziehl-Neelsen acid-fast stain. Rod-shaped pink/red cells are observed. Which organism is most likely present?

Accepted Answer

Mycobacterium tuberculosis

Question 3

Which component of the Gram-negative bacterial cell wall is responsible for its endotoxin activity?

Accepted Answer

Lipid A of lipopolysaccharide (LPS)

Question 4

A bacterium is observed to move toward a light source. This behavior is best described as:

Accepted Answer

Phototaxis

Question 5

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

Accepted Answer

It protects the cell from desiccation and phagocytosis.

Question 6

Which of the following transport mechanisms requires energy and moves substances against their concentration gradient?

Accepted Answer

Active transport

Question 7

A laboratory technician observes a clear halo around rod-shaped bacterial cells after staining. What structure is being visualized?

Accepted Answer

Capsule

Question 8

Which of the following statements about endospores is TRUE?

Accepted Answer

Endospores are resistant to heat, radiation, and chemicals due to their protective layers and dehydrated core.

Question 9

Which of the following best describes the arrangement of cocci in 'streptococci'?

Accepted Answer

Cocci arranged in chains

Question 10

A Gram stain is performed on a bacterial sample. After decolorization, the cells appear pink. What does this indicate about the cell wall structure?

Accepted Answer

The cells have a thin peptidoglycan layer and an outer membrane.

Question 11

Which of the following is a function of bacterial fimbriae?

Accepted Answer

Attachment to surfaces and biofilm formation

Question 12

Which of the following best explains why Mycobacterium tuberculosis is acid-fast?

Accepted Answer

Its cell wall contains mycolic acid, a waxy lipid.

Question 13

Which of the following is TRUE regarding plasmids in bacteria?

Accepted Answer

They can confer resistance to antibiotics.

Question 14

A bacterial cell is placed in a hypertonic solution. What will most likely happen to the cell?

Accepted Answer

Water will flow out of the cell, causing plasmolysis.

Question 15

Which of the following best describes the function of the bacterial cell wall?

Accepted Answer

It protects the cell from osmotic lysis and provides structural support.

Question 16

Which of the following is a distinguishing feature of Gram-positive bacteria?

Accepted Answer

Thick peptidoglycan layer with teichoic acids

Question 17

Which of the following best describes group translocation in bacteria?

Accepted Answer

A substance is chemically altered as it is transported into the cell.

Question 18

Which of the following is a function of the bacterial plasma membrane?

Accepted Answer

It acts as a selectively permeable barrier and is involved in energy transformation.

Question 19

Which of the following statements about bacterial ribosomes is correct?

Accepted Answer

They are 70S in size and are the sites of protein synthesis.

Question 20

A patient is diagnosed with a urinary tract infection caused by Proteus species. Which structure is most likely involved in the bacteria's ability to colonize the urinary tract?

Accepted Answer

Fimbriae

Prokaryotic Cell Structure, Morphology, and Staining in Microbiology

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