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Microbiology (Bio305) > Chapter 2 > Flashcards

Chapter 2 Flashcards

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1
Q

What is resolution?

A

The smallest distance by which two objects can be separated and still be distinguished.

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2
Q

What part of the human eye has the finest resolution of two separate points?

A

Fovea

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3
Q

What is detection mean?

A

The ability to determine the presence of an object

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4
Q

What is magnification?

A

This means an increase in the apparent size of an image to resolve smaller separations between objects

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5
Q

What are some characteristics of eukaryotic microbes?

A
  1. Protozoa, algae, or fungi
  2. 10-100 um
    Structures can be seen under a light microscope
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6
Q

What are some characteristics of prokaryotic microbes?

A
  1. Bacteria or Archaea
  2. .4-10 um
  3. Subcellular structures too small to resolve by light microscopy
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7
Q

What shape do bacilli refer to?

A

Rods

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8
Q

What shape do cocci refer to?

A

spheres

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9
Q

What shape do spirochetes or spirilla refer to?

A

Spirals

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10
Q

What is the wavelength of visible light (in nm)?

A

400-750nm

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11
Q

What three conditions must exist for electromagnetic radiation to resolve an object?

A
  1. Contrast between the object and it’s medium
  2. Wavelength smaller than the object
  3. Magnification
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12
Q

What is absorption?

A

This means that the photon’s energy is acquired by the absorbing light.

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13
Q

What does reflection mean?

A

This means that the wavefront bounces off the surface of an object.

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14
Q

What does refraction mean?

A

This means that the light bends as it enters a substance that slows its speed.

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15
Q

What does scattering mean?

A

This occurs when the wavefront interacts with an object smaller than the wavelength of light.

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16
Q

What requires the bending of light?

A

Magnification

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17
Q

How does refraction accomplish magnification?

A

Refraction magnifies an image when light passes through a refractive material shaped so as to spread its rays.

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18
Q

What does a lens of a microscope do?

A

The lens bends the light rays to intersect at a focal point.

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19
Q

What is a focal point?

A

The point of which parallel rays bend at an angle such to all hit the same point.

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20
Q

What ultimately limits the ability of what we can see with a microscope?

A

Resolution

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21
Q

What is empty magnification?

A

magnification increasing without detail

22
Q

What limits the resolution of detail in microscopy?

A

The wave nature of light

23
Q

What is Bright-field Microscopy?

A

Generates a dark image of an object over a light background

24
Q

Name 5 ways to increase resolution.

A
  1. Use shorter wavelength of light
  2. Reduce Contrast
  3. Use immersion oil
  4. Use wider lens close to specimen
  5. Higher numerical aperture
25
Q

What is a compound microscope?

A

A system of multiple lenses designed to correct or compensate for aberration.

26
Q

What is total magnification?

A

Magnification of the ocular multiplied by that of the objective

27
Q

What are the advantages of wet mounts?

A
  1. Observation of cells in natural state
28
Q

What are the disadvantages of wet mounts?

A
  1. Little contrast between cell and background

2. Sample may dry out to quick

29
Q

What is fixation?

A

Cells are made to adhere to a slide in a fixed position

30
Q

What is staining?

A
  1. Cells are given a distinct color

2. Most stains have conjugated double bonds or aromatic rings, as well as one or more positive charges

31
Q

What is a simple stain?

A

adds dark color specifically to cells, but not to the external medium or surrounding tissue

32
Q

What is a differential stain?

A

stains one kind of cell but not another

33
Q

Who developed the Gram stain in 1884?

A

Hans Christian Gram

34
Q

What does Gram-positive mean?

A

peptidoglycan is present in the layer

35
Q

What does Gram-negative mean?

A

peptidoglycan is not present in the layer

36
Q

In what type of microscopy does the specimen absorb light of a defined wavelength and then emits light of lower energy?

A

Fluorescence Microscopy

37
Q

What is the excitation wavelength?

A

light absorbed by the specimen

38
Q

What is the emission wavelength?

A

light emitted by the specimen

39
Q

What is a fluorophore?

A

fluorescent chemical compound

40
Q

Who tracked the movement of DNA binding proteins during cell fission?

A

Lucy Shapiro and Moerner

41
Q

What does phase-contrast microscopy exploit?

A

differences in the relative index between the cytoplasm and the surrounding medium or between organelles.

42
Q

What is differential interference contrast microscopy?

A

enhances contrast by superimposing an image of the specimen onto a second beam of light that generates interference fringes

43
Q

What must be present in order to use electron microscopy?

A
  1. The specimen must absorb electrons

2. The specimen must be coated with heavy metal

44
Q

What is a transmission electron microscopy?

A

Reveals internal structures

45
Q

Wha is a scanning electron microscopy?

A

Reveals external structures in 3D

46
Q

What are two ways a specimen may be prepared for electron microscopy?

A
  1. Embedded in a polymer for thin sections(using microtome)

2. Sprayed onto copper grid

47
Q

Cryo-electron Microscopy

A
  1. no staining

2. Specimen must be flash frozen

48
Q

Tomography

A

the acquisition of projected images from different angles of a transparent specimen

49
Q

Cryo-electron tomography

A
  1. avoids the need to physically slice the sample
50
Q

What does scanning probe microscopy enable?

A

nanoscale observation of cells

51
Q

What is the major tool to visualize a molecule?

A

X-ray diffraction analysis, or X-ray crystallography

Microbiology (Bio305) (7 decks)

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