Question 1

Which of the following best explains why the limit of resolution for a light microscope is approximately $$0.2\ \mu m$$?

Accepted Answer

Because the wavelength of visible light and the numerical aperture together set a physical limit, as described by $$d=0.5\lambda/	ext{numerical aperture}.$$

Question 2

A microbiologist observes a specimen under a compound microscope using a 40X objective and a 10X ocular lens. What is the total magnification?

Accepted Answer

$$400	imes$$

Question 3

During a Gram stain, why do Gram-positive bacteria retain the crystal violet-iodine complex after alcohol decolorization?

Accepted Answer

Their thick peptidoglycan layer becomes dehydrated, trapping the complex inside.

Question 4

Which of the following statements about fluorescence microscopy is correct?

Accepted Answer

It relies on the emission of light of one color when illuminated with another color.

Question 5

Which microscopy technique would be most appropriate for visualizing the three-dimensional structure of a biofilm?

Accepted Answer

Confocal scanning laser microscopy (CSLM)

Question 6

A scientist wants to observe the surface details of a bacterial cell at very high magnification. Which instrument should they use?

Accepted Answer

Scanning electron microscope (SEM)

Question 7

Which of the following best describes the main chemical difference between bacterial and archaeal cytoplasmic membranes?

Accepted Answer

Bacterial membranes contain ester linkages in phospholipids, while archaeal membranes contain ether linkages.

Question 8

Which of the following is a function of the cytoplasmic membrane in prokaryotes?

Accepted Answer

Energy conservation via generation of a proton motive force

Question 9

A bacterium is observed to have a high surface-to-volume ratio. What is a likely advantage of this characteristic?

Accepted Answer

It supports greater nutrient exchange per unit cell volume.

Question 10

Which of the following transport systems in prokaryotes involves chemical modification of the transported substance?

Accepted Answer

Group translocation

Question 11

Which component of the Gram-negative cell envelope is responsible for its toxicity and is also known as endotoxin?

Accepted Answer

Lipid A of lipopolysaccharide (LPS)

Question 12

Which of the following statements about peptidoglycan is FALSE?

Accepted Answer

It is found in both Bacteria and Archaea.

Question 13

Which of the following best describes the function of porins in Gram-negative bacteria?

Accepted Answer

They allow the passage of hydrophilic low-molecular-weight substances through the outer membrane.

Question 14

Which of the following cell surface structures is primarily involved in the attachment of bacteria to surfaces and resistance to phagocytosis?

Accepted Answer

Capsule

Question 15

Which of the following is TRUE about endospores?

Accepted Answer

They are highly resistant to heat, chemicals, and radiation.

Question 16

A scientist observes a bacterium with a spiral shape and a flexible cell wall. Which term best describes its morphology?

Accepted Answer

Spirochete

Question 17

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

Accepted Answer

Presence of pseudomurein instead of peptidoglycan

Question 18

Which of the following best explains why mycoplasmas are resistant to antibiotics that target peptidoglycan synthesis?

Accepted Answer

They lack peptidoglycan in their cell envelope.

Question 19

Which of the following statements about bacterial flagella is correct?

Accepted Answer

They move by rotation powered by the proton motive force.

Question 20

A bacterium is observed to move rapidly and spin around its axis. Which flagellar arrangement is most likely present?

Accepted Answer

Polar

Microbial Cell Structure and Function: Microscopy, Cell Walls, and Membrane Transport

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