Question 1

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

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer with teichoic acids, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing LPS.

Question 2

Which component of the Gram-negative outer membrane is responsible for its endotoxin activity?

Accepted Answer

Lipid A

Question 3

A patient develops severe diarrhea and hemolytic-uremic syndrome after eating undercooked beef. The causative agent expresses O157 and H7 antigens. Which structure is responsible for the O157 antigen?

Accepted Answer

O-specific polysaccharide of LPS

Question 4

Which of the following statements about Mycoplasma pneumoniae is correct?

Accepted Answer

It is resistant to beta-lactam antibiotics because it lacks peptidoglycan.

Question 5

Which of the following best explains why gas vesicles are advantageous for planktonic cyanobacteria?

Accepted Answer

They decrease cell density, allowing cells to float and access light.

Question 6

Which of the following is a function of bacterial capsules?

Accepted Answer

Assist in attachment to surfaces and protect against desiccation

Question 7

A bacterium is observed to move in a straight line, then suddenly change direction. Which motility mechanism and behavior is most likely being observed?

Accepted Answer

Flagellar swimming with run-and-tumble behavior

Question 8

Which of the following cell inclusions is correctly matched with its function?

Accepted Answer

Polyphosphate granules – storage of inorganic phosphate

Question 9

Which of the following statements about endospores is FALSE?

Accepted Answer

Endospores are produced by some Gram-negative bacteria.

Question 10

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

Accepted Answer

They are covalently bound to peptidoglycan and contribute to cell wall rigidity.

Question 11

Which of the following is a unique feature of archaeal cell walls compared to bacterial cell walls?

Accepted Answer

Presence of pseudomurein and S-layers

Question 12

A researcher inserts a capillary tube containing glucose into a suspension of motile bacteria. Over time, bacteria accumulate near the tube. What process is being measured?

Accepted Answer

Chemotaxis

Question 13

Which of the following best explains why Mycoplasma species are resistant to penicillin?

Accepted Answer

They lack peptidoglycan, the target of penicillin.

Question 14

Which of the following is NOT a function of fimbriae in bacteria?

Accepted Answer

Facilitation of genetic exchange via conjugation

Question 15

Which of the following best describes the arrangement of flagella in a bacterium that moves rapidly and spins around its axis?

Accepted Answer

Polar

Question 16

Which of the following is a correct statement about the proton turbine model of flagellar motility?

Accepted Answer

Proton flow across the membrane drives rotation of the flagellum.

Question 17

Which of the following is a correct match between a cell surface structure and its function?

Accepted Answer

Pili – genetic exchange via conjugation

Question 18

Which of the following is a correct description of the ecological role of gliding motility?

Accepted Answer

Enables surface colonization and spreading in biofilms

Question 19

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

Accepted Answer

It is located between the cytoplasmic membrane and the outer membrane.

Question 20

Which of the following is a correct statement about the function of small acid-soluble spore proteins (SASPs) in endospores?

Accepted Answer

They protect spore DNA from UV radiation and heat.

Microbial Cell Structure and Function: Cell Walls, Surface Structures, and Motility

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