Deck 2: Observing the Microbial Cell

Question 1

The highest useful magnification for a light microscope is about

A) 100X.
B) 1,000X.
C) 10,000X.
D) 100,000X.
E) 1,000,000X.

Answer 1

C

Question 2

A ball-shaped microbe is referred to as a

A) bacillus.
B) coccus.
C) vibrio.
D) strepto.
E) spirochete.

Answer 2

B

Question 3

Resolution is the smallest distance by which two objects can be ________ and still be ________.

A) magnified; seen
B) separated; distinguished
C) magnified; separated
D) distinguished; separated
E) magnified; distinguished

Answer 3

C

Question 4

Which of these series arranges microbes from smallest to largest?

A) virus $$\rightarrow$$ bacterium $$\rightarrow$$ red blood cell $$\rightarrow$$ paramecium

B) virus $$\rightarrow$$ red blood cell $$\rightarrow$$ bacterium $$\rightarrow$$ paramecium

C) bacterium $$\rightarrow$$ virus $$\rightarrow$$ paramecium $$\rightarrow$$ red blood cell

D) bacterium $$\rightarrow$$ virus $$\rightarrow$$ red blood cell $$\rightarrow$$ paramecium

E) paramecium $$\rightarrow$$ red blood cell $$\rightarrow$$ bacterium $$\rightarrow$$ virus

Question 5

One advantage of a wet mount is

A) low contrast.
B) that the organism is still.
C) viewing in a natural state.
D) high contrast.
E) that the sample does not overheat.

Question 6

If aqueous cytoplasm was submerged in a beaker of immersion oil, the slide would be

A) undetectable.
B) brighter than its surroundings.
C) darker than its surroundings.
D) fluorescent.
E) stained.

Question 7

The part of the human eye that is MOST involved in resolving an image is the

A) iris.
B) lens.
C) optic nerve.
D) retina.
E) cornea.

Question 8

When two waves are out of phase by ________ wavelength, they produce destructive interference, canceling each other's amplitude and resulting in contrast in the image.

A) one-tenth of a
B) one-eighth of a
C) one-quarter of a
D) one-half of a
E) one

Question 9

Increasing the refractive index of the medium between the object and the objective lens increases

A) refraction.
B) reflection.
C) magnification.
D) resolution.
E) wavelength.

Question 10

As lens strength increases, the light cone ________ and the lens must be ________ the object.

A) narrows; nearer to
B) narrows; farther from
C) widens; nearer to
D) widens; farther from
E) widens; touching

Question 11

Label the condenser in the figure below.

A) A
B) B
C) C
D) D
E) E

Question 12

What happens if the wavelength of radiation is larger than the object being viewed?

A) absorption
B) scattering
C) no resolution
D) refraction
E) resolution

Question 13

Staining helps to visualize bacteria by increasing the

A) size of the cells.
B) motility of the cells.
C) contrast of the image.
D) magnification of the image.
E) aberration of the image.

Question 14

Which of these arranges the steps of the Gram stain into the correct order?

A) iodine $$\rightarrow$$ crystal violet $$\rightarrow$$ decolorizer $$\rightarrow$$ safranin

B) safranin $$\rightarrow$$ decolorizer $$\rightarrow$$ crystal violet $$\rightarrow$$ iodine

C) crystal violet $$\rightarrow$$ decolorizer $$\rightarrow$$ iodine $$\rightarrow$$ safranin

D) crystal violet $$\rightarrow$$ decolorizer $$\rightarrow$$ safranin $$\rightarrow$$ iodine

E) crystal violet $$\rightarrow$$ iodine $$\rightarrow$$ decolorizer $$\rightarrow$$ safranin

Question 15

Malachite green is commonly used to stain

A) eukaryotic cells.
B) Gram-negative cells.
C) Gram-positive cells.
D) bacterial endospores.
E) acid-fast cells.

Question 16

Chlamydia trachomatis transmits infection to a new cell via

A) a membrane vesicle.
B) elementary bodies.
C) amoeba.
D) host membranes.
E) the human cell.

Question 17

What is the MOST important property that enables a lens to magnify an image?

A) absorption
B) fluorescence
C) reflection
D) refraction
E) scattering

Question 18

Wavelength interference results in small observed objects (like bacteria) being surrounded by

A) a capsule.
B) a membrane.
C) concentric rings.
D) a dark field.
E) a cell wall.

Question 19

What would happen if a lens had the same refractive index as air?

A) Light would not pass through the lens.
B) The image would be magnified more than with a glass lens.
C) The image would be magnified, but the resolution would be less than with a glass lens.
D) The image would be magnified, and the resolution would be greater than with a glass lens.
E) The image would not be magnified.

Question 20

A(n) ________ acts to vary the diameter of the light column in a light microscope.

A) condenser
B) objective
C) ocular
D) diaphragm
E) lens

Question 21

Which of the following is best visualized using a negative stain?

A) Gram-negative cell wall
B) acid-fast cell wall
C) capsule
D) endospores
E) flagella

Question 22

Which of these techniques can be used to localize the DNA sequence at the origin of replication in a bacterial cell?

A) fluorescence microscopy
B) phase contrast
C) X-ray diffraction
D) atomic force microscopy
E) cryo-EM

Question 23

Which type of microscopy is used to identify the 3-D structure of biofilms?

A) phase-contrast
B) dark-field
C) florescent
D) bright-field
E) confocal

Question 24

What is the total magnification of a light microscope when using a 25X ocular and 40X objective lens?

A) 15X
B) 65X
C) 400X
D) 1,000X
E) 1,200X

Question 25

What is the best explanation for a Gram-positive bacterium appearing pink after performing a Gram stain?

A) The crystal violet was left on for too long.
B) The iodine was left on for too long.
C) The decolorizer was left on for too long.
D) The safranin was left on for too long.
E) The stain was properly performed.

Question 26

In which type of microscopy do dust particles interfere the MOST?

A) bright-field
B) dark-field
C) phase-contrast
D) interference
E) fluorescence

Question 27

What molecule is shown below?

A) GFP
B) FM4-64
C) DNA
D) RNA
E) DAPI

Question 28

Which type of microscopy gives a "false 3-D image"?

A) Gram stain
B) nuclear magnetic resonance
C) scanning electron
D) negative stain
E) differential interference contrast

Question 29

Which two components of the Gram stain form a complex that is retained by Gram-positive cells?

A) crystal violet and iodine
B) safranin and iodine
C) crystal violet and safranin
D) alcohol and safranin
E) alcohol and iodine

Question 30

Fluorescent microscopy that absorbs light at 260m would MOST likely fluoresce at

A) 100 nm.
B) 200 nm.
C) 260 nm.
D) 400 nm.
E) 800 nm.

Question 31

What is the best explanation for a Gram-negative bacterium appearing purple after performing a Gram stain?

A) The safranin was not applied.
B) The decolorizer was not applied.
C) The iodine was not applied.
D) The crystal violet was not applied.
E) The stain was properly performed.

Question 32

A useful application of dark-field optics is the study of bacterial

A) motility.
B) surfaces.
C) interiors.
D) shape.
E) structure.

Question 33

What happens to an electron when excited by light at the excitation wavelength?

A) It remains in the same orbital.
B) It moves to a lower energy orbital.
C) It moves to a higher energy orbital.
D) It emits a photon.
E) It is filtered.

Question 34

Which of the following techniques are based upon wave interference?

A) X-ray diffraction and phase contrast microscopy
B) phase contrast and dark-field microscopy
C) bright-field and dark-field microscopy
D) X-ray diffraction and atomic force microscopy
E) scanning and transmission electron microscopy

Question 35

Which of the following is an advantage of using chemical imaging microscopy?

A) observing an organism in its living environment
B) displaying plankton
C) measuring pH within a cell
D) showing distribution of chemicals in a cell
E) pinpointing a protein location

Question 36

Which type of microscopy is used to view the internal structures of a specimen?

A) light
B) atomic force
C) scanning electron
D) transmission electron
E) confocal fluorescence

Question 37

The knife used to cut embedded specimens for observation by transmission electron microscopy is called a

A) crystallographer.
B) microtome.
C) grid.
D) polymer.
E) scalpel.

Question 38

Fluorescence microscopy using labeled antibodies is referred to as

A) immunofluorescence.
B) autofluorescence.
C) confocal microscopy.
D) phase-contrast microscopy.
E) dark-field microscopy.

Question 39

Atomic force microscopy measures ________ between a probe and an object to map the three-dimensional topography of a cell.

A) hydrogen bonds
B) covalent interactions
C) van der Waals forces
D) pH changes
E) magnetic interactions

Question 40

Which of these numeric aperture and light combinations would give the best resolution?

A) numeric aperture = 0.8, wavelength = 600 nm
B) numeric aperture = 0.8, wavelength = 500 nm
C) numeric aperture = 1.0, wavelength = 700 nm
D) numeric aperture = 1.0, wavelength = 600 nm
E) numeric aperture = 0.8, wavelength = 400 nm

Question 41

Which of these techniques would provide the best resolution of an enzyme's structure?

A) scanning electron microscopy
B) transmission electron microscopy
C) cryo-EM
D) X-ray diffraction analysis
E) atomic force microscopy

Question 42

The spots recorded on film during X-ray diffraction analyses are due to

A) artifacts.
B) scattering.
C) wave interference.
D) absorption.
E) fluorescence.

Question 43

Cryo-electron microscopy (cryo-EM) is differentiated from transmission electron microscopy because it

A) requires making thin slices of the sample to be viewed.
B) does not require staining with heavy metals.
C) may be used to view living tissues.
D) uses a weaker electron beam.
E) can provide a color image of the microbial cell.

Question 44

Describe three conditions that are necessary for electromagnetic radiation to resolve an object.

Question 45

If your eyes had photoreceptors packed as closely as an eagle's (about eight times greater than humans), would you be able to resolve a virus (100 nm in size) using a light microscope? Why or why not?

Question 46

Compare and contrast the radiation sources, lenses, and image-capturing devices used in light microscopy and transmission electron microscopy.

Question 47

Compare and contrast a simple stain (like methylene blue) with the Gram stain. What information about a microbial sample can be collected with each?

Question 48

Which type of microscopy is particularly useful to study the surfaces of live bacteria?

A) atomic force
B) scanning electron
C) transmission electron
D) dark-field
E) bright-field

Question 49

What color are Gram-positive and Gram-negative cells when properly Gram stained? For each step of the Gram-stain procedure, predict the colors of a Gram-positive or Gram-negative cell if that step were omitted during staining. Explain your reasoning.

Question 50

Which of the following techniques can visualize bacteria without focusing electromagnetic radiation?

A) cryo-electron microscopy
B) phase-contrast microscopy
C) dark-field microscopy
D) atomic force microscopy
E) X-ray diffraction

Question 51

Microbes were detected long before the invention of the microscope. How could this be?

Question 52

Transmission electron microscopy commonly has a resolution of ________ the highest resolution possible for light microscopy.

A) 10X
B) 100X
C) 1,000X
D) 10,000X
E) 1,000,000X

Question 53

List and describe three common shapes of bacteria.

Question 54

List and briefly describe four ways that light interacts with objects.

Question 55

List three different differential stains used in microbiology. What can be detected with each?

Question 56

Which of the following would be MOST appropriate to visualize viral particles being assembled inside an infected bacterial cell?

A) dark-field microscopy
B) atomic force microscopy
C) fluorescence microscopy
D) scanning electron microscopy
E) transmission electron microscopy

Question 57

Are all bacilli Bacillus? Explain.

Question 58

The digitally combined images of cryo-EM can achieve resolution comparable to that of

A) scanning electron microscopy.
B) transmission electron microscopy.
C) interference microscopy.
D) X-ray crystallography.
E) dark-field microscopy.

Question 59

Why do some bacteria appear purple after being Gram stained, while others appear pink?

Question 60

Which of the following methods is used to generate the structure shown below?

A) scanning probe microscopy
B) scanning electron microscopy
C) transmission electron microscopy
D) confocal microscopy
E) X-ray crystallography

Question 61

The figure below shows the Gram-staining process. Describe what is happening at step number 3 relative to bacterial cell walls.

Question 62

Explain why components from thermophilic bacteria take less X-ray damage than other bacteria.

Question 63

The figure below displays absorption and emission spectra for a fluorophore. Describe the difference between absorption and emission and how this is reflected in the figure.

Question 64

Using the figure below, explain how the visualization of molecules occurs through X-ray crystallography.

Question 65

Define a fluorophore and give three examples of how it can be used to label cells.

Question 66

Why are stains used in microscopy? Compare and contrast the stains used in light versus electron microscopy.

Question 67

Give a few reasons why living organisms may not be observed by transmission electron microscopy (TEM) or scanning electron microscopy (SEM).

Question 68

Most electron micrographs in microbiology textbooks are in color. Is this normal for an electron micrograph? Why or why not?

Question 69

Describe three methods of sample preparation for electron microscopy. Which method would cause the fewest artifacts? Why?