Microbiology: An Evolving Science 3rd Edition Test Bank by Joan L. Slonczewski, John W. Foster – Digital Download File

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Observing the Microbial Cell
MULTIPLE CHOICE
1. Who proved that stomach ulcers are caused by a bacterium?
a. Hooke d. Jenner
b. Marshall e. van Leeuwenhoek
c. Gram
ANS: B DIF: Easy REF: Introduction TOP: VI
MSC: Remembering
2. The part of the human eye that is most involved in resolving an image is the:
a. iris d. retina
b. lens e. cornea
c. optic nerve
ANS: D DIF: Medium REF: 2.1 TOP: I.A
MSC: Remembering
3. A ball-shaped microbe is referred to as a:
a. bacillus d. strepto
b. coccus e. spirochete
c. vibrio
ANS: B DIF: Easy REF: 2.1 TOP: I.C.ii.b
MSC: Remembering
4. Resolution is the smallest distance by which two objects can be __________ and still be __________.
a. magnified; seen d. distinguished; separated
b. separated; distinguished e. magnified; distinguished
c. magnified; separated
ANS: B DIF: Medium REF: 2.1 TOP: I.A.i
MSC: Understanding
5. 400 nm is equivalent to:
a. 4.0 x 10-5 m d. 4.0 x 10-8 m
b. 4.0 x 10-6 m e. 4.0 x 10-9 m
c. 4.0 x 10-7 m
ANS: C DIF: Medium REF: 2.1 TOP: I.A
MSC: Applying
6. Which of these series arranges microbes from smallest to largest?
a. virus  bacterium  red blood cell  paramecium
b. virus  red blood cell  bacterium  paramecium
c. bacterium  virus  paramecium  red blood cell
d. bacterium  virus  red blood cell  paramecium
e. paramecium  red blood cell  bacterium  virus
ANS: A DIF: Difficult REF: 2.1 TOP: I.C
MSC: Applying

7. The heating of water when exposed to light is primarily due to:
a. reflection d. scattering
b. refraction e. fluorescence
c. absorption
ANS: C DIF: Difficult REF: 2.2 TOP: II.B.i.a
MSC: Remembering
8. Wavelength interference results in small observed objects (like bacteria) being surrounded by:
a. a capsule d. a dark field
b. a membrane e. a cell wall
c. an Airy disk
ANS: C DIF: Medium REF: 2.2 TOP: II.C
MSC: Remembering
9. What is the most important property that enables a lens to magnify an image?
a. absorption d. refraction
b. fluorescence e. scattering
c. reflection
ANS: D DIF: Medium REF: 2.2 TOP: II.C
MSC: Understanding
10. 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 d. one-half of a
b. one-eighth of a e. one
c. one-quarter of a
ANS: D DIF: Difficult REF: 2.2 TOP: II.D
MSC: Understanding
11. Increasing the refractive index of the medium between the object and the objective lens increases:
a. refraction d. resolution
b. reflection e. wavelength
c. magnification
ANS: D DIF: Difficult REF: 2.2 TOP: II.D
MSC: Understanding
12. If a glass slide was submerged in a beaker of immersion oil, the slide would be:
a. undetectable d. fluorescent
b. brighter than its surroundings e. stained
c. darker than its surroundings
ANS: A DIF: Medium REF: 2.2 TOP: II.A.ii.a
MSC: Applying
13. 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.

ANS: E DIF: Medium REF: 2.2 TOP: II.C
MSC: Applying
14. The highest useful magnification for a light microscope is about:
a. 100X d. 100,000X
b. 1,000X e. 1,000,000X
c. 10,000X
ANS: C DIF: Medium REF: 2.2 TOP: II.D
MSC: Applying
15. A(n) __________ acts to vary the diameter of the light column in a light microscope.
a. condenser d. diaphragm
b. objective e. lens
c. ocular
ANS: D DIF: Easy REF: 2.3 TOP: III.B.i
MSC: Remembering
16. Which of these arranges the steps of the Gram stain into the correct order?
a. iodine  crystal violet  decolorizer  safranin
b. safranin  decolorizer  crystal violet  iodine
c. crystal violet  decolorizer  iodine  safranin
d. crystal violet  decolorizer  safranin  iodine
e. crystal violet  iodine  decolorizer  safranin
ANS: E DIF: Medium REF: 2.3 TOP: III.E.ii.a
MSC: Remembering
17. When Gram stained, most eukaryotes appear:
a. colorless d. green
b. purple e. black
c. pink
ANS: C DIF: Medium REF: 2.3 TOP: III.E.ii.a
MSC: Remembering
18. Malachite green is commonly used to stain:
a. eukaryotic cells d. bacterial endospores
b. Gram-negative cells e. acid-fast cells
c. Gram-positive cells
ANS: D DIF: Medium REF: 2.3 TOP: III.E.ii.c
MSC: Remembering
19. As lens strength increases, the light cone __________ and the lens must be __________ the object.
a. narrows; nearer to d. widens; farther from
b. narrows; farther from e. widens; touching
c. widens; nearer to
ANS: C DIF: Medium REF: 2.3 TOP: III.A
MSC: Understanding
20. Staining helps to visualize bacteria by:
a. increasing the size of the cells

b. increasing the motility of the cells
c. increasing the contrast of the image
d. increasing the magnification of the image
e. increasing the aberration of the image
ANS: C DIF: Medium REF: 2.3 TOP: III.D.iii
MSC: Understanding
21. In a proper Gram stain, positive cells are stained by:
a. crystal violet only
b. safranin only
c. both crystal violet and safranin
d. neither crystal violet nor safranin
e. not enough information has been provided to know
ANS: C DIF: Medium REF: 2.3 TOP: III.E.ii.a
MSC: Understanding
22. Which two components of the Gram stain form a complex that is retained by Gram-positive cells?
a. crystal violet and iodine d. alcohol and safranin
b. safranin and iodine e. alcohol and iodine
c. crystal violet and safranin
ANS: A DIF: Medium REF: 2.3 TOP: III.E.ii.a
MSC: Understanding
23. Which of the following is best visualized using a negative stain?
a. Gram-negative cell wall d. endospores
b. acid-fast cell wall e. flagella
c. capsule
ANS: C DIF: Medium REF: 2.3 TOP: III.E.ii.d
MSC: Understanding
24. 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
ANS: E DIF: Difficult REF: 2.3 TOP: III.A
MSC: Applying
25. What is the total magnification of a light microscope when using a 25X ocular and 40X objective lens?
a. 15X d. 1,000X
b. 65X e. 1,200X
c. 400X
ANS: D DIF: Medium REF: 2.3 TOP: III.B.i
MSC: Applying
26. 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.
ANS: C DIF: Difficult REF: 2.3 TOP: III.E.ii.a
MSC: Analyzing
27. 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.
ANS: B DIF: Difficult REF: 2.3 TOP: III.E.ii.a
MSC: Analyzing
28. A useful application of dark-field optics is the study of bacterial:
a. motility d. shape
b. surfaces e. structure
c. interiors
ANS: A DIF: Medium REF: 2.4 TOP: IV.A
MSC: Remembering
29. 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
ANS: A DIF: Medium REF: 2.4 TOP: IV.A | IV.B
MSC: Understanding
30. In which type of microscopy do dust particles interfere the most?
a. bright-field microscopy d. interference microscopy
b. dark-field microscopy e. fluorescence microscopy
c. phase-contrast microscopy
ANS: B DIF: Easy REF: 2.4 TOP: IV.A.iii
MSC: Understanding
31. Which of the following would be best suited to observe the motility of microbial cells?
a. Gram stain d. negative stain
b. nuclear magnetic resonance e. phase-contrast microscopy
c. scanning electron microscopy
ANS: E DIF: Medium REF: 2.4 TOP: IV.B
MSC: Understanding
32. DAPI is a dye that is commonly used in _____________ microscopy.
a. bright-field d. confocal
b. dark-field e. fluorescence
c. phase contrast

ANS: E DIF: Medium REF: 2.5 TOP: V.B.i
MSC: Remembering
33. A fluorophore used in fluorescence microscopy that absorbs light at 260 nm would most likely
fluoresce at:
a. 100 nm d. 400 nm
b. 200 nm e. 800 nm
c. 260 nm
ANS: D DIF: Difficult REF: 2.5 TOP: V.A
MSC: Understanding
34. The fluorophore DAPI specifically binds:
a. the cytoplasm d. RNA
b. the cell wall e. DNA
c. protein
ANS: E DIF: Easy REF: 2.5 TOP: V.B.i
MSC: Understanding
35. The aromatic groups of the fluorophore DAPI associate exclusively with the:
a. cell wall d. cell membrane
b. base pairs of DNA e. pili
c. flagella
ANS: B DIF: Medium REF: 2.5 TOP: V.B.i
MSC: Understanding
36. Fluorescence microscopy using labeled antibodies is referred to as:
a. immunofluorescence d. phase-contrast microscopy
b. autofluorescence e. dark-field microscopy
c. confocal microscopy
ANS: A DIF: Easy REF: 2.5 TOP: V.B.ii
MSC: Understanding
37. Which of the following can be used to localize proteins in a microbial cell?
a. DAPI and immunofluorescence
b. acridine orange and green fluorescent protein (GFP) fusions
c. DAPI and acridine orange
d. GFP fusions and immunofluorescence
e. DAPI and GFP fusions
ANS: D DIF: Difficult REF: 2.5 TOP: V.B.ii | V.B.iii
MSC: Understanding
38. Which of these techniques can be used to localize the DNA sequence at the origin of replication in a
bacterial cell?
a. fluorescence microscopy d. atomic force microscopy
b. phase contrast e. cryo-EM
c. X-ray diffraction
ANS: A DIF: Difficult REF: 2.5 TOP: V.B.iv
MSC: Understanding

39. Which form of microscopy is used with DNA microarrays to observe differences in gene expression?
a. light microscopy d. transmission electron microscopy
b. atomic force microscopy e. confocal fluorescence microscopy
c. scanning electron microscopy
ANS: E DIF: Difficult REF: 2.5 TOP: V.C
MSC: Understanding
40. The knife used to cut embedded specimens for observation by transmission electron microscopy is
called a:
a. crystallographer d. polymer
b. microtome e. scalpel
c. grid
ANS: B DIF: Easy REF: 2.6 TOP: VI.B.i
MSC: Remembering
41. Atomic force microscopy measures __________ between a probe and an object to map the
three-dimensional topography of a cell.
a. hydrogen bonds d. pH changes
b. covalent interactions e. magnetic interactions
c. van der Waals forces
ANS: C DIF: Easy REF: 2.6 TOP: VI.D.ii
MSC: Remembering
42. Which type of microscopy is particularly useful to study the surfaces of live bacteria?
a. atomic force d. dark-field
b. scanning electron e. bright-field
c. transmission electron
ANS: A DIF: Easy REF: 2.6 TOP: VI.D.ii
MSC: Remembering
43. Transmission electron microscopy commonly has a resolution of __________ times the highest
resolution possible for light microscopy.
a. 10 d. 10,000
b. 100 e. 1,000,000
c. 1,000
ANS: C DIF: Difficult REF: 2.6 TOP: VI.A
MSC: Understanding
44. Which of the following would be most appropriate to visualize viral particles being assembled inside
an infected bacterial cell?
a. dark-field microscopy d. scanning electron microscopy
b. atomic force microscopy e. transmission electron microscopy
c. fluorescence microscopy
ANS: E DIF: Medium REF: 2.6 TOP: VI.A | VI.B
MSC: Understanding
45. A microscopic structure that is interpreted incorrectly is a/an:
a. microtome d. antibody
b. crystal e. artifact
c. shadow

ANS: E DIF: Easy REF: 2.6 TOP: VI.C.i
MSC: Understanding
46. Unlike transmission electron microscopy, cryo-electron microscopy:
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
ANS: B DIF: Medium REF: 2.6 TOP: VI.D
MSC: Understanding
47. The digitally combined images of cryo-EM can achieve resolution comparable to that of:
a. scanning electron microscopy d. X-ray crystallography
b. transmission electron microscopy e. dark-field microscopy
c. interference microscopy
ANS: D DIF: Difficult REF: 2.6 TOP: VI.D.i
MSC: Understanding
48. Which of the following techniques can visualize bacteria without focusing electromagnetic radiation?
a. cryo-electron microscopy d. atomic force microscopy
b. phase-contrast microscopy e. X-ray diffraction
c. dark-field microscopy
ANS: D DIF: Medium REF: 2.6 TOP: VI.D.ii
MSC: Understanding
49. The spots recorded on film during X-ray diffraction analyses are due to:
a. artifacts d. absorption
b. scattering e. fluorescence
c. wave interference
ANS: C DIF: Medium REF: 2.7 TOP: VII.A.i
MSC: Understanding
50. Which of these techniques would provide the best resolution of an enzyme’s structure?
a. scanning electron microscopy d. X-ray diffraction analysis
b. transmission electron microscopy e. atomic force microscopy
c. cryo-EM
ANS: D DIF: Medium REF: 2.7 TOP: VII.A.i
MSC: Understanding
SHORT ANSWER
1. List and describe three common shapes of bacteria.
ANS:
Bacilli (bacillus in the singular) are rod-shaped bacteria. Cocci (singular, coccus) are spherical-shaped
bacteria. Spirochetes are tightly coiled spirals or corkscrew-shaped bacteria.
DIF: Easy REF: 2.1 TOP: I.C.ii MSC: Remembering

2. Microbes were detected long before the invention of the microscope. How could this be?
ANS:
Detection is the ability to observe the presence of an object, such as when we detect a group of bacteria
in a culture tube or growing on a surface like a food product. Even though we can detect the group, we
can’t resolve individual cells without the magnification afforded by microscopes.
DIF: Easy REF: 2.1 TOP: I.B.i MSC: Understanding
3. Are all bacilli Bacillus? Explain.
ANS:
No. Bacillus refers to a particular genus of organisms that are commonly found in the soil. Although
they are rod-shaped, the members of this genus are not the only bacteria that have this cellular
morphology. The term bacillus refers to any rod-shaped microbe, which means that not all bacilli
belong to the genus Bacillus.
DIF: Easy REF: 2.1 TOP: I.C.ii MSC: Understanding
4. 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?
ANS:
No. Although your resolving power would be much improved, the light microscope’s power will still
be limited by the wavelengths of light that you can see (roughly 400 nm for human eyes). Objects less
than 400 nm cannot be resolved by light in the visible spectrum.
DIF: Medium REF: 2.1 TOP: I.A MSC: Applying
5. Describe three conditions that are necessary for electromagnetic radiation to resolve an object.
ANS:
There must be contrast between the object and its surroundings. The wavelength of the radiation must
be equal to or smaller than the size of the object. The detector must have sufficient resolution for the
given wavelength.
DIF: Medium REF: 2.2 TOP: II.A.ii MSC: Remembering
6. List and briefly describe four ways that light interacts with objects.
ANS:
(1) Absorption: light energy is absorbed by an object. (2) Reflection: a wavefront bounces off of an
object at an angle equal to its incident angle. (3) Refraction: bending of light when it enters a substance
that slows its speed. (4) A scattering wavefront interacts with an object of smaller dimensions than the
wavelength.
DIF: Medium REF: 2.2 TOP: II.B.i MSC: Remembering
7. Compare and contrast a simple stain (like methylene blue) with the Gram stain. What information
about a microbial sample can be collected with each?
ANS:

Both staining procedures colorize bacterial cells, thereby increasing the sample’s contrast and
improving resolution. A simple stain will color all microbial cells uniformly. This allows one to record
the relative size, shape, and arrangement of any cells present. The Gram stain is a differential stain. In
addition to size, shape, and arrangement, this procedure allows one to determine if the cells have a
Gram-positive (purple) or Gram-negative (pink) cell wall structure.
DIF: Medium REF: 2.3 TOP: III.E.i MSC: Understanding
8. List three different differential stains used in microbiology. What can be detected with each?
ANS:
The most common differential stain is the Gram stain. This procedure allows one to distinguish
between cells having one membrane (Gram-positive) and two membranes (Gram-negative). Another
common differential stain is the acid-fast stain. Carbolfuchsin stains the mycolic acid–containing
acid-fast cells of the genus Mycobacterium. The endospore stain is a differential stain that stains
endospores with malachite green. Negative staining and antibody staining are also included in the text.
DIF: Medium REF: 2.3 TOP: III.E.ii MSC: Understanding
9. 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.
ANS:
Properly Gram stained Gram-positive cells are purple and Gram-negative are pink.
(1) Skipping primary stain (crystal violet): Gram-positive and Gram-negative would both be pink.
No crystal violet–iodide complex would be formed in the Gram-positive wall. All cells would be
decolorized and take on the color of safranin.
(2) Skipping mordant (iodine): Gram-positive and Gram-negative would both be pink. No crystal
violet–iodine complex would be formed in the Gram-positive wall. All cells would be decolorized and
take on the color of safranin.
(3) Skipping decolorizer (alcohol): Gram-positive and Gram-negative would both be purple. The
crystal violet–iodine complex would remain in all cells. Although safranin still binds, the purple color
is so much more intense that the pink of the safranin cannot be seen.
(4) Skipping secondary stain (safranin): Gram-positive cells would be purple. The Gram-negative
cells would be colorless. The dye complex will be removed from the Gram-negative cells, but they
will be difficult to see since the counterstain was not applied.
DIF: Medium REF: 2.3 TOP: III.E.ii.a MSC: Understanding
10. Why do some bacteria appear purple after being Gram stained, while others appear pink?
ANS:
Gram-negative cells have a few layers of peptidoglycan cell wall and an outer lipopolysaccharide
membrane. Gram-positive organisms have several layers of peptidoglycan and no outer membrane.
The multiple layers of peptidoglycan retain the crystal violet–iodine complex, so appear purple.
Gram-negative cells do not retain the crystal violet because there are few layers of peptidoglycan and
the outer membrane is disrupted by the decolorizer.
DIF: Medium REF: 2.3 TOP: III.E.ii.a MSC: Understanding
11. Compare and contrast the radiation sources, lenses, and image-capturing devices used in light
microscopy and transmission electron microscopy.

ANS:
The radiation source for light microscopy is a light, whereas for electron microscopy it is an electron
source or tungsten filament. The lenses in the light microscope are glass, whereas magnets are used in
electron microscopy. The lenses have similar functions and are arranged in the same order in both
types of microscopy. Light microscopy uses a condenser lens, whereas the lens in electron microscopy
is called the projection lens. The image-capturing device for light is the human eye, or sometimes a
camera. The image-capturing device for electron microscopy is a fluorescent screen.
DIF: Difficult REF: 2.3 | 2.6 TOP: III.B | VI.A MSC: Understanding
12. Why are stains used in microscopy? Compare and contrast the stains used in light versus electron
microscopy.
ANS:
Stains are used to increase the contrast between an object and its surroundings, so as to make it visible.
The stains used in light microscopy are usually charged and interact with different cellular
components. Positively charged dyes bind to negatively charged cell surfaces. They also are colored,
so they impart color to a cell or its components. The stains used for electron microscopy are heavy
metals or salts, which increase the density of certain components, again increasing contrast. In electron
microscopy, the image of the microbe is always black and white.
DIF: Difficult REF: 2.3 | 2.6 TOP: III.D | VI.B MSC: Understanding
13. Name two types of microscopy that are suitable for directly studying bacterial motility. What
interaction of light with the microbe is most important for each of these techniques?
ANS:
Either dark-field or phase-contrast microscopy could be used. In dark-field microscopy, the condenser
contains an opaque disk held by three ―spider legs‖ across an open ring. No light travels directly up
through the specimen, so the only light that reaches the eye is light that is scattered by objects on the
slide. This scattered light allows detection of objects that are too small to be resolved by light rays.
Phase-contrast microscopy exploits differences in refractive index between cell components and
transforms them into differences in intensity of transmitted light due to wave interference.
DIF: Medium REF: 2.4 TOP: IV.A | IV.B MSC: Understanding
14. If you are interested in studying the localization of a protein in a bacterial cell, what techniques would
provide you with the best information?
ANS:
Fluorescence microscopy can be used to study protein localization. One method would be to use
fluorescently tagged antibodies to detect the proteins using immunofluorescence microscopy. Another
possibility would be to make green fluorescent protein fusions with the protein of interest. These
hybrid proteins would fluoresce wherever they are in the cell.
DIF: Difficult REF: 2.5 TOP: V.B MSC: Understanding
15. Define a fluorophore and give three examples of how it can be used to label cells.
ANS:

A fluorophore is a fluorescent molecule that can be used to stain a specimen for observation with a
fluorescence microscope. Some fluorophores, such as DAPI, have affinity for certain cell chemicals.
Antibodies can be labeled with fluorescent dyes and reacted with specific targets in
immunofluorescence. Short sequences of DNA attached to a fluorophore can be used to hybridize and
label target DNA.
DIF: Difficult REF: 2.5 TOP: V.B MSC: Understanding
16. Archaea and Bacteria differ in the genetic sequences of their ribosomal RNA genes. How can this
difference be used to microscopically differentiate between members of these domains?
ANS:
Short DNA sequences that are homologous to either the Bacterial or Archaeal sequences can be
conjugated to fluorophores that emit different wavelength light. These probes will anneal to the
complementary DNA in the corresponding cells in a sample. When viewed using a fluorescence
microscope, the archaeal and bacterial cells will have different colors. This is referred to as
fluorescence in situ hybridization, or FISH, analysis.
DIF: Difficult REF: 2.5 TOP: V.B.iv MSC: Applying
17. Most electron micrographs in microbiology textbooks are in color. Is this normal for an electron
micrograph? Why or why not?
ANS:
Electron micrographs are not naturally colored. The original image is produced when the electrons
bombard a fluorescent screen. The resultant image is processed by a computer to appear as black and
white with intensities in the entire range of grays in between. These images are later colorized using
computer software (like Photoshop) to improve the aesthetics and provide additional information.
DIF: Difficult REF: 2.6 TOP: VI.A MSC: Understanding
18. Give a few reasons why living organisms may not be observed by transmission electron microscopy
(TEM) or scanning electron microscopy (SEM).
ANS:
In TEM, the specimens are fixed and embedded into a polymer for sectioning. The specimen is then
stained with heavy metal to increase contrast. In SEM, the entire organism is shadowed with heavy
metal prior to observation. Most importantly, however, the entire optical column of the EM must be
maintained under vacuum, and a living specimen would be quickly destroyed by an electron beam.
DIF: Easy REF: 2.6 TOP: VI.A | VI.B MSC: Understanding
19. Describe three methods of sample preparation for electron microscopy. Which method would cause
the fewest artifacts? Why?
ANS:
(1) Samples can be embedded in a polymer and cut into thin sections with a microtome, then coated
with a heavy metal. (2) Samples can be sprayed onto a copper grid, then treated with a heavy metal.
(3) Samples may be flash frozen for cryo-electron microscopy. Cryo-EM will cause the fewest
artifacts. When using this technique, the cells are not fixed or artificially stained. Instead, the cells are
flash frozen—leaving the cell components still hydrated and closest to their original state.
DIF: Medium REF: 2.6 TOP: VI.B MSC: Understanding