Question 1

During the Gram staining procedure, what is the primary reason that gram-positive bacteria retain the crystal violet stain after the alcohol decolorization step?

Accepted Answer

Because their thick peptidoglycan layer traps the crystal violet-iodine complex.

Question 2

Penicillin is less effective against gram-negative bacteria. Which structural feature is primarily responsible for this reduced effectiveness?

Accepted Answer

The presence of an extra outer membrane that blocks penicillin entry.

Question 3

Which of the following statements accurately compares gram-positive and gram-negative bacteria?

Accepted Answer

Gram-negative bacteria have thinner cell walls than gram-positive bacteria.

Question 4

A patient develops a persistent infection due to a bacterial biofilm on a catheter. Which component is most responsible for the stability and protection of this biofilm?

Accepted Answer

Extracellular polymeric substances

Question 5

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

Accepted Answer

Energy storage

Question 6

A researcher is studying bacterial adherence to host tissues. Which structure is most directly involved in this process?

Accepted Answer

Pili

Question 7

Which of the following statements about fimbriae is correct?

Accepted Answer

They can facilitate genetic recombination.

Question 8

Spirochetes are unique among bacteria because they possess which of the following structures for motility?

Accepted Answer

Axial filaments

Question 9

A bacterium is observed to have flagella distributed all over its surface. What is the correct term for this flagellar arrangement?

Accepted Answer

Peritrichous flagella

Question 10

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

Accepted Answer

They provide motility by acting as whip-like structures.

Question 11

A bacterium with multiple flagella located at one end is described as:

Accepted Answer

Lophotrichous

Question 12

A hospital-acquired infection is traced to a biofilm on a medical device. Which property of the biofilm most contributes to its resistance to antibiotics?

Accepted Answer

The extracellular polymeric substances limit antibiotic penetration.

Question 13

Which of the following equations best represents the relationship between the rate of diffusion ($$D$$), surface area ($$A$$), concentration gradient ($$\Delta C$$), and thickness of the membrane ($$d) in $$bacterial nutrient uptake?

Accepted Answer

$$ J = D \frac{A \Delta C}{d} $$

Question 14

A scientist is designing an experiment to test the effect of removing the capsule from a pathogenic bacterium. Which outcome is most likely?

Accepted Answer

The bacterium will become more susceptible to phagocytosis by immune cells.

Question 15

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

Accepted Answer

Their outer membrane acts as a barrier to many drugs.

Question 16

A clinical isolate is found to adhere strongly to host tissues and resist washing away. Which structure is most likely responsible for this property?

Accepted Answer

Fimbriae

Question 17

Which of the following is a key difference between capsules and slime layers in bacteria?

Accepted Answer

Capsules are well-organized and firmly attached, while slime layers are loosely attached and unorganized.

Question 18

A bacterium is described as amphitrichous. What does this mean about its flagella?

Accepted Answer

It has a single flagellum at each end of the cell.

Question 19

Which of the following best describes the role of pili in bacterial conjugation?

Accepted Answer

They form a bridge between two cells to transfer genetic material.

Question 20

A microbiologist observes a bacterium with a single flagellum at one pole. What is the correct term for this arrangement?

Accepted Answer

Monotrichous

Microbiology Study Guide: Prokaryotic Cell Structures & Functions

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