Chapter 2 : Microscopy Flashcards

1
Q

What type of microscope was first invented and is the most widely used today?

A

Light microscope

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2
Q

What is the resolution limit in a light microscope?

A

0.2 um ( micrometer)

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3
Q

what is refractive index?

A

a measure of how much a substance slows the velocity of light

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4
Q

When light passes from one medium to another, what happens to the light?

A

refracted (bent)

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5
Q

In regards to lenses they focus light rays at a specific place called?

A

focal point

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6
Q

what kind of microscope would be used to observe stained or unstained specimens to produce a dark image with a bright background and have different magnification?

A

Bright-field Microscope

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7
Q

what is total magnification?

A

the product of ocular lenses and objective lenses

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8
Q

The ability of a lens to distinguish objects from each other rather than a single larger object is ?

A

Resolution

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9
Q

the shorter the wavelength their is less resolution T or F?

A

F The greater the resolution

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10
Q

what is the distance between the front surface of the lens and the surface of the cover glass or specimen when it is in sharp focus called?

A

working distance

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11
Q

what three microscopes may be used to gain better contrast between the cells and it structures ?

A

dark field
phase contrast
differential interference contract
(DIC)

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12
Q

what kind of microscope would produce a bright image against a dark background?

A

Dark field Microscope

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13
Q

How is the image produced in a Dark field microscope?

A

light being refracted or reflected by specimen

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14
Q

How is the image produced in a phase contrast microscope ?

A

produces an image of a darker microbe against a lighter background?

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15
Q

How does DIC microscopes create images ?

A

detect differences in refractive indices and thickness in different part of specimen

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16
Q

In a fluorescence microscopes how is the image produced?

A

by exciting a specimen with a wavelength of light that triggers the object to emit fluorescence light

17
Q

In a fluorescence microscope what do we use to stain the microbe?

A

fluorochromes - absorb and emit visible fluorescent light

18
Q

What are fluorochromes?

A

labeled probes- antibodies or fluorochrome tags

19
Q

Why do we prepare and stain specimen?

A

increase visibility
accentuate specifics in morphology
preservation specimen

20
Q

Scientists want stained cells to resemble living cells as closely as possible, what process is used to preserve the internal and external structures?

21
Q

How does Fixation preserve internal and external structures?

A

By inactivating enzymes that tell cell morphology to toughen up

22
Q

There are two type of heat fixation, what are they?

A

Heat fixation: preserves morphology but destroys subcell structures
Chemical fixation: protects fine sub cell structure and morphology

23
Q

Ionizable dyes have charged groups, basic dye have negative charge and acidic dyes have positive charges T o F ?

A

False
basic +
Acidic -

24
Q

Describe what simple staining is?

A
  • Uses one stain
  • used to determine size, shape and bacteria arrangement
25
Describe what differential staining does ?
divides organisms into groups based on staining
26
Gram stain and acid fast stain are what kind of staining ?
differential staining
27
differential staining is used to detect the presence or absence of what structures?
Capsules and flagella
28
what are the differences between a gram-positive bacteria and a gram-negative bacteria?
gram + have a thicker peptidoglycan layer gram - have an outer membrane and an inner membrane with a thin peptidoglycan layer
29
Why is acid-fast staining more useful for staining bacteria members of myobacterium?
due to having a cell wall of lipids, it prevents dye to bind
30
Capsule staining is used for?
used to visualize polysaccharide capsules around bacteria
31
How may capsules appear in negative staining ?
colorless against stained background
32
what is used to provide information about the presence and distribution pattern of flagella?
flagella staining
33
The electron wavelength is 100,00x shorter than visible light, resulting in a higher resolution image T o F?
True
34
what occurs in electron microscopy?
electrons replace the light as a beam
35
how does TEM work?
electrons pass through the specimen to form image
36
How does SEM work to produce an image?
uses excited electrons from the surface of specimen to make image
37
What is the purpose for Cryo-electron microscopy?
used to see biomolecules like proteins to see high resolution structures