Deck 2: Observing the Microbial Cell

Question 1

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
B) one-eighth
C) one-quarter
D) one-half
E) one

Answer 1

D

Question 2

Magnification without resolution is known as __________ magnification.

A) complete
B) zero
C) maximum
D) total
E) empty

Answer 2

E

Question 3

A rod-shaped microbe is referred to as a:

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

Answer 3

A

Question 4

The total __________ of the microscope is obtained by multiplying the magnification of the ocular lens by that of the objective lens.

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

Question 5

If you are using a microscope with a 10× ocular lens and a 100× objective, what is the total magnification?

A) 10-fold
B) 100-fold
C) 110-fold
D) 1,000-fold
E) This is not enough information.

Question 6

One __________ is one-thousandth of a millimeter.

A) micrometer
B) nanometer
C) meter
D) centi
E) kilo

Question 7

All electromagnetic radiation travels through a vacuum at what speed?

A) 3 × 10⁸ mm/sec
B) 3 × 10⁸ cm/sec
C) 3 × 10⁸ m/sec
D) 3 × 10⁸ ft/sec
E) 3 × 10⁸ mph

Question 8

An image is magnified when light passes through a refractive material shaped so as to __________ its rays.

A) absorb
B) block
C) concentrate
D) condense
E) spread

Question 9

Who compared "small animals" from his teeth before and after drinking coffee?

A) Hooke
B) Fleming
C) Gram
D) Jenner
E) van Leeuwenhoek

Question 10

In humans, resolution is achieved by focusing an image on a retina, packed with light-absorbing:

A) rods
B) cones
C) nerves
D) photoreceptor cells
E) lenses

Question 11

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; touch

Question 12

If an object and its surroundings absorb or reflect radiation equally then the object will be:

A) undetectable
B) reflected
C) refracted
D) radiated
E) fluoresced

Question 13

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

A) reflection
B) resolution
C) frequency
D) refraction
E) wavelength

Question 14

With the 100× lens, the refractive index of light passing through the specimen is maintained by insertion of __________, with a refractive index comparable to that of glass.

A) immersion oil
B) water
C) air
D) bacteria
E) stain

Question 15

Higher-power lenses require more light and thus an open:

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

Question 16

Which is the most important property that enables a lens to magnify an image?

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

Question 17

A/An __________ acts to vary the diameter of the light column in a light microscope.

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

Question 18

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 19

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

Question 20

Having fewer photoreceptors per surface area means higher:

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

Question 21

Gram's iodine is the __________ in the Gram staining procedure.

A) primary stain
B) counterstain
C) decolorizer
D) negative stain
E) mordant

Question 22

Observations of bacterial flagella during motility are best suited to:

A) bright-field microscopy
B) dark-field microscopy
C) SEM
D) TEM
E) NMR

Question 23

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

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

Question 24

Which form of microscopy is based on the difference in refractive index between cell components and the surrounding medium?

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

Question 25

The __________ in the Gram stain process binds to the crystal violet, generating a complex that is held more tightly within the cell.

A) mordant
B) safranin
C) alcohol
D) bacteria
E) slide

Question 26

Which of the following staining processes requires crystal violet?

A) acid-fast stain
B) antibody stain
C) negative stain
D) Gram stain
E) spore stain

Question 27

When light is absorbed by an object and emitted at a longer wavelength, it is referred to as:

A) fluorescence
B) magnification
C) reflection
D) refraction
E) radiation

Question 28

The fluorophore acridine orange specifically binds:

A) cytoplasm
B) cell wall
C) protein
D) RNA
E) DNA

Question 29

Which of the following is a true statement about Gram staining?

A) The Gram stain differentiates between the three domains.
B) In a Gram-negative cell, the crystal violet-iodide complex is retained by multiple layers of peptidoglycan.
C) The outer membrane is disrupted by the decolorizer.
D) Human cells appear Gram-positive.
E) The mordant is used so that Gram-negative cells may be observed.

Question 30

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

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

Question 31

Which is the counterstain in the Gram stain procedure?

A) crystal violet
B) methylene blue
C) malachite green
D) safranin
E) Gram's iodine

Question 32

Which form of microscopy is used with DNA microarrays to observe differences in gene expression?

A) light microscopy
B) atomic force microscopy
C) SEM
D) TEM
E) confocal fluorescence microscopy

Question 33

Fluorescence requires excitation and emission at different:

A) refractive indexes
B) wavelengths
C) contrasts
D) refractions
E) densities

Question 34

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

A) SEM
B) TEM
C) interference microscopy
D) X-ray crystallography
E) dark-field microscopy

Question 35

In fluorescence microscopy, incident light is absorbed by the specimen and reemitted at a __________ energy, resulting in a __________.

A) lower; longer wavelength
B) lower; shorter wavelength
C) higher; longer wavelength
D) higher; shorter wavelength
E) higher; higher contrast

Question 36

The aromatic groups of the fluorophore DAPI associate exclusively with the:

A) cell wall
B) base pairs of DNA
C) flagella
D) cell membrane
E) pili

Question 37

Which of the following is a negative stain?

A) acid-fast stain
B) endospore stain
C) antibody stain
D) simple stain
E) capsule stain

Question 38

X-ray diffraction and phase contrast microscopy both involve:

A) wave interference
B) observation of living specimens
C) differential stains
D) simple stains
E) shadowing.

Question 39

The use of antibodies linked to fluorophores is known as:

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

Question 40

Eukaryotes stain:

A) Gram-neutral
B) Gram-positive
C) Gram-negative
D) blue
E) no color

Question 41

List and describe three common shapes of bacteria.

Question 42

Fixatives and heavy atom stains used in EM can introduce __________ into an image.

A) colors
B) resolution
C) refraction
D) artifacts
E) fluorescence

Question 43

A microscopic structure that is interpreted incorrectly is a/an:

A) microtome
B) crystal
C) shadow
D) antibody
E) artifact

Question 44

In which one of the following types of microscopy is the specimen shadowed with heavy metal?

A) atomic force microscopy
B) SEM
C) TEM
D) X-ray diffraction
E) dark-field

Question 45

Briefly explain why or how fixatives and stains used in microscopy may introduce artifacts. How might this be determined?

Question 46

In __________, because the frozen sample remains hydrated, the biological molecules retain the same conformation as in solution.

A) cryo-EM
B) TEM
C) SEM
D) fluorescence microscopy
E) laser confocal microscopy

Question 47

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

A) atomic force
B) SEM
C) TEM
D) dark-field
E) bright-field

Question 48

Compare and contrast the radiation source, the lenses, and the image-capturing device in light and TEM.

Question 49

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

Question 50

Explain when you would use Bacillus versus bacillus.

Question 51

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

Question 52

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

A) ten
B) one hundred
C) one thousand
D) ten thousand
E) one million

Question 53

Which of the following is true of transmission electron microscopy but NOT scanning electron microscopy?

A) The specimen is usually fixed and embedded.
B) The embedded specimen is cut into thin sections with a microtome.
C) The specimen is stained with heavy metal.
D) The specimen is viewed as three-dimensional.
E) The requirement for a vacuum precludes the viewing of live organisms.

Question 54

The knife used to cut embedded specimens for observation by TEM is called a:

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

Question 55

Why is it possible to detect microbes but NOT resolve them?

Question 56

Describe the lens system of a compound microscope including the location of each lens and the purpose of each.

Question 57

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

Question 58

Which technique uses interference patterns from crystallized macromolecules to determine structure at atomic resolution?

A) SEM
B) TEM
C) cryo-EM
D) X-ray diffraction analysis
E) atomic force microscopy

Question 59

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 60

What does the phrase "eagle-eyed" mean? Describe why it is scientifically accurate.

Question 61

Give a few reasons why living organisms may NOT be observed by TEM or SEM.

Question 62

How does laser scanning confocal microscopy produce images?

Question 63

Why do some bacteria appear purple after being Gram stained and other appear red?

Question 64

Why is it that a photographic image from an electron microscope is black and white?

Question 65

Explain phase-contrast microscopy and give one advantage and one disadvantage of phase-contrast microscopy.

Question 66

Explain how the modified condenser in dark-field microscopy is used to make small microbes visible. Give one advantage and one disadvantage of dark-field microscopy.

Question 67

Compare and contrast simple and differential stains. Give examples of each.

Question 68

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

Question 69

Briefly state the steps in the Gram stain procedure. What would happen if you accidentally forgot to use the counterstain?

Question 70

Describe three methods of sample preparation for electron microscopy.