Question 1

A microbe measures 10 μm in length. How long is this in nanometers (nm)?

Accepted Answer

$$1 	imes 10^4$ nm$

Question 2

Which of the following best explains why electron microscopes have greater resolution than light microscopes?

Accepted Answer

Electrons have a much shorter wavelength than visible light.

Question 3

If a microscope has a resolution of 0.2 nm, what does this mean?

Accepted Answer

It can distinguish two points that are at least 0.2 nm apart as separate.

Question 4

Which group would a 250 nm microbe most likely belong to?

Accepted Answer

Chlamydia or Mycoplasma

Question 5

Why doesn’t a negative stain color a cell?

Accepted Answer

The stain is repelled by the cell’s negatively charged surface.

Question 6

Why is the Gram stain so useful in microbiology?

Accepted Answer

It differentiates bacteria based on cell wall composition.

Question 7

Which step in the Gram stain procedure could be omitted and still allow differentiation between Gram-positive and Gram-negative cells?

Accepted Answer

Application of the counterstain (safranin)

Question 8

Using a compound light microscope with a resolving power of $$0.3 \ \mu m$$, a $$10	imes$$ ocular lens, and a $$100	imes$$ oil immersion lens, would you be able to discern two objects separated by $$0.3 \ \mu m$$?

Accepted Answer

Yes, because the separation equals the resolving power.

Question 9

Endospores can be seen as refractile structures in unstained cells and as colorless areas in Gram-stained cells. Why is it necessary to do an endospore stain to verify the presence of endospores?

Accepted Answer

Endospore stains specifically color endospores, confirming their identity.

Question 10

A laboratory diagnosis of Neisseria gonorrhoeae infection is based on microscopic examination of Gram-stained pus. What is the disease caused by this bacterium?

Accepted Answer

Gonorrhea

Question 11

A sample of vaginal discharge shows large (10 μm) nucleated red cells coated with small (0.5 μm × 1.5 μm) blue cells. What is the most likely explanation for the red and blue cells?

Accepted Answer

Red cells are epithelial cells, blue cells are bacteria.

Question 12

Which of the following is a characteristic of Helicobacter pylori as described in the clinical case?

Accepted Answer

It is associated with peptic ulcers.

Question 13

What is the formula to convert micrometers (μm) to nanometers (nm)?

Accepted Answer

$$1 \ \mu m = 10^3$ \ nm$$

Question 14

Which unit is commonly used to measure the wavelength of visible light?

Accepted Answer

Nanometers (nm)

Question 15

Which of the following best describes the relationship between wavelength and resolution in microscopy?

Accepted Answer

Shorter wavelengths provide higher resolution.

Question 16

A student observes a specimen using a light microscope with a total magnification of $$1000	imes. If $$the ocular lens is $$10	imes$$, what is the magnification of the objective lens?

Accepted Answer

$$100	imes$$

Question 17

Which of the following microbes would be best visualized using an electron microscope rather than a light microscope?

Accepted Answer

Viruses (20–250 nm)

Question 18

If you move from micrometers (μm) to millimeters (mm), how do you convert the value?

Accepted Answer

Divide by 1000

Question 19

Which property of light is most important for determining the resolution of a microscope?

Accepted Answer

Wavelength

Question 20

A Gram-stained sample shows purple cocci and pink rods. What does this indicate about the sample?

Accepted Answer

Both Gram-positive cocci and Gram-negative rods are present.

Microscopy and Microbial Cell Structure: Study Guidance for Chapter 3

Study Guide - Practice Questions

Study Guide - Flashcards