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, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharide.

Question 2

A clinical isolate of Streptococcus pneumoniae is found to produce a capsule. What is the most likely consequence of this trait?

Accepted Answer

The bacterium will be more pathogenic because the capsule protects it from phagocytosis.

Question 3

Which arrangement describes a group of spherical bacteria in clusters?

Accepted Answer

Staphylococci

Question 4

A bacterial cell is observed to move toward a light source. Which structure is most likely responsible for this behavior?

Accepted Answer

Flagella

Question 5

Which of the following statements about peptidoglycan is correct?

Accepted Answer

It is a complex polysaccharide that provides rigidity to the bacterial cell wall.

Question 6

A patient is diagnosed with tuberculosis. Which staining technique would be most appropriate to identify the causative organism?

Accepted Answer

Acid-fast stain

Question 7

Which of the following best explains why Mycobacterium tuberculosis does not stain well with the Gram stain?

Accepted Answer

It has a high lipid content in its cell wall that prevents dye uptake.

Question 8

Which bacterial shape is described as spiral and includes genera such as Vibrio and Spirochete?

Accepted Answer

Spiral

Question 9

A bacterium is described as pleomorphic. What does this mean?

Accepted Answer

It can exist in multiple shapes.

Question 10

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

Accepted Answer

Providing motility

Question 11

Which of the following equations best represents the relationship between cell surface area ($$A) $$and volume ($$V) $$for a spherical bacterium of radius $$r$$?

Accepted Answer

$$A = 4 \pi r^2$, V$$ = \frac{4}{3} \pi $$r^3$$

Question 12

Which of the following best describes the clinical relevance of peptidoglycan in bacterial cell walls?

Accepted Answer

It is the target of antibiotics such as penicillin.

Question 13

Which of the following statements about fimbriae is correct?

Accepted Answer

Fimbriae help bacteria attach to surfaces.

Question 14

A bacterium is observed to be penicillin resistant and has an outer membrane. Which group does it most likely belong to?

Accepted Answer

Gram-negative bacteria

Question 15

Which of the following is a differential stain used to distinguish between major groups of bacteria based on cell wall composition?

Accepted Answer

Gram stain

Question 16

Which of the following genera is known for lacking a cell wall?

Accepted Answer

Mycoplasma

Question 17

Which of the following best explains why bacterial cell walls prevent cells from rupturing in hypotonic environments?

Accepted Answer

The cell wall maintains the shape and provides rigidity, resisting osmotic pressure.

Question 18

Which of the following is NOT a typical arrangement of bacilli?

Accepted Answer

Tetrads

Question 19

Which of the following statements about the slime layer is correct?

Accepted Answer

It is loosely attached and helps bacteria adhere to surfaces.

Question 20

A bacterium is observed to be monomorphic. What does this indicate about its morphology?

Accepted Answer

It has a single, consistent shape.

Structure, Classification, and Characteristics of Bacterial Cells

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