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Microbiology (Bio305) > Chapter 2 > Flashcards

Chapter 2 Flashcards

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
What is a compound microscope?
A system of multiple lenses designed to correct or compensate for aberration.
26
What is total magnification?
Magnification of the ocular multiplied by that of the objective
27
What are the advantages of wet mounts?
1. Observation of cells in natural state
28
What are the disadvantages of wet mounts?
1. Little contrast between cell and background | 2. Sample may dry out to quick
29
What is fixation?
Cells are made to adhere to a slide in a fixed position
30
What is staining?
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
What is a simple stain?
adds dark color specifically to cells, but not to the external medium or surrounding tissue
32
What is a differential stain?
stains one kind of cell but not another
33
Who developed the Gram stain in 1884?
Hans Christian Gram
34
What does Gram-positive mean?
peptidoglycan is present in the layer
35
What does Gram-negative mean?
peptidoglycan is not present in the layer
36
In what type of microscopy does the specimen absorb light of a defined wavelength and then emits light of lower energy?
Fluorescence Microscopy
37
What is the excitation wavelength?
light absorbed by the specimen
38
What is the emission wavelength?
light emitted by the specimen
39
What is a fluorophore?
fluorescent chemical compound
40
Who tracked the movement of DNA binding proteins during cell fission?
Lucy Shapiro and Moerner
41
What does phase-contrast microscopy exploit?
differences in the relative index between the cytoplasm and the surrounding medium or between organelles.
42
What is differential interference contrast microscopy?
enhances contrast by superimposing an image of the specimen onto a second beam of light that generates interference fringes
43
What must be present in order to use electron microscopy?
1. The specimen must absorb electrons | 2. The specimen must be coated with heavy metal
44
What is a transmission electron microscopy?
Reveals internal structures
45
Wha is a scanning electron microscopy?
Reveals external structures in 3D
46
What are two ways a specimen may be prepared for electron microscopy?
1. Embedded in a polymer for thin sections(using microtome) | 2. Sprayed onto copper grid
47
Cryo-electron Microscopy
1. no staining | 2. Specimen must be flash frozen
48
Tomography
the acquisition of projected images from different angles of a transparent specimen
49
Cryo-electron tomography
1. avoids the need to physically slice the sample
50
What does scanning probe microscopy enable?
nanoscale observation of cells
51
What is the major tool to visualize a molecule?
X-ray diffraction analysis, or X-ray crystallography

Microbiology (Bio305) (7 decks)

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