Question 1

Which of the following units is most appropriate for measuring the diameter of a typical bacterial cell?

Accepted Answer

Micrometers ($$\mum)$$

Question 2

A compound light microscope has an objective lens with 40x magnification and an ocular lens with 10x magnification. What is the total magnification?

Accepted Answer

$$40 	imes 10 = 400$$

Question 3

Which property of a microscope determines its ability to distinguish two closely spaced points as separate entities?

Accepted Answer

Resolution

Question 4

Why is immersion oil used with the oil immersion objective lens in light microscopy?

Accepted Answer

To reduce light refraction and increase resolution

Question 5

Which type of microscopy would be most appropriate for observing live, unstained microorganisms such as Treponema pallidum?

Accepted Answer

Darkfield microscopy

Question 6

A researcher wants to visualize the three-dimensional surface structure of a bacterium at high resolution. Which microscopy technique should they use?

Accepted Answer

Scanning electron microscopy (SEM)

Question 7

Which of the following best describes the main difference between electron microscopy and light microscopy?

Accepted Answer

Electron microscopy uses electrons, which have a shorter wavelength than visible light, resulting in higher resolution

Question 8

Which staining technique would you use to differentiate between bacteria with thick and thin peptidoglycan cell walls?

Accepted Answer

Gram stain

Question 9

After performing a Gram stain, what color would you expect a Gram-negative bacterium to appear after the counterstain step?

Accepted Answer

Pink/red

Question 10

Which of the following best explains why basic dyes are commonly used to stain bacterial cells?

Accepted Answer

Bacterial cells have a negative charge and attract the cationic chromophore of basic dyes

Question 11

A clinical sample is suspected to contain Mycobacterium tuberculosis. Which staining technique would be most appropriate for rapid identification?

Accepted Answer

Acid-fast stain

Question 12

Which of the following statements about fluorescence microscopy is correct?

Accepted Answer

It uses ultraviolet light to excite fluorochromes, which then emit visible light

Question 13

Which microscopy technique allows for the visualization of living cells up to 1 millimeter deep and can track cell activity in real time?

Accepted Answer

Two-photon microscopy

Question 14

A scientist wants to map the atomic structure of a DNA molecule without modifying the specimen. Which technique should they use?

Accepted Answer

Scanning tunneling microscopy (STM)

Question 15

Which of the following stains is used to visualize bacterial capsules?

Accepted Answer

Capsule stain

Question 16

What is the main advantage of using a phase-contrast microscope over a brightfield microscope for observing living cells?

Accepted Answer

It provides greater contrast and allows visualization of internal structures without staining

Question 17

Which of the following best describes the function of a mordant in staining procedures?

Accepted Answer

It increases the affinity of the stain for the specimen

Question 18

A sample is stained with an acidic dye. What is the most likely result?

Accepted Answer

The background will be stained, leaving the cells colorless (negative staining)

Question 19

Which microscopy technique is most suitable for studying cells attached to surfaces, such as bacterial biofilms or arterial plaque, using sound waves?

Accepted Answer

Scanning acoustic microscopy (SAM)

Question 20

During Gram staining, what is the primary reason that Gram-negative bacteria lose the crystal violet stain after the alcohol wash?

Accepted Answer

They have a thin peptidoglycan layer and an outer membrane that allows the stain to be washed out

Microscopy: Observing Microorganisms Through a Microscope

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