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Microbiology > Lecture 4 > Flashcards

Lecture 4 Flashcards

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Biology 101 flashcards
1
Q

What are the two main types of microscopes

A
  1. Light

2. Electron

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2
Q

What are 3 types of electron microscopes?

A
  1. Transmission Electron Microscopy
  2. Scanning Electron Microscopy
  3. Scanning Tunneling Microscopy
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3
Q

What is a light microscope?

A

Any microscope that uses visible light to observe specimens

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4
Q

What are the two lenses that are used in a light microscope?

A
  1. Objective Lens

2. Ocular Lens

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5
Q

Where is a objective lens located and what does it do?

A

Closest to the slide

Magnifies the specimen 10-100x

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6
Q

Where is the ocular lens located and what does it do?

A

Within the eyepiece of the microscope

Magnifies specimen 10x

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7
Q

How do you figure out the magnification of a compound microscope?

A

Objective lens magnification x ocular lens magnification

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8
Q

What is resolution?

A

The ability to distinguish fine detail and structure, two 2 points a certain distance apart

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9
Q

In order for two objects to be seen as distinct from one another what must happen

A

Light must pass between

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10
Q

Short wavelengths= ________ energy =_______ resolution

A

Higher energy, higher resolution

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11
Q

What is the general principle of resolution

A

The shorter the wavelength of the light, the better the resolution to be

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12
Q

How do electron microscopes work?

A

Use a beam of electrons instead of light

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13
Q

Are electron waves longer or shorter than light waves?

A

Much shorter

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14
Q

Can electron microscopes achieve less or greater resolution compared to a light microscope

A

Much greater (up to 500,000x)

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15
Q

What is the smallest object visible with the human eye?

A

0.10 mm

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16
Q

How small can a compound microscopes view objects? Electron?

A

Electron- 0.2 nanometres

Compound- 0.2 um

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17
Q

What is a transmission electron microscope used to examine?

A

Internal Cell Structure

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18
Q

What is thin sectioning

A

Cell being cut in order to be viewed

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19
Q

Can transmission electron microscopes see through a cell?

A

no, the electron beams do not penetrate the thick cell wall

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20
Q

What is an example of a stain used when thin sectioning?

A

Uranium

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21
Q

Scanning electron microscopes view what?

A

Only the surface of an object

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22
Q

What is required to view something with a scanning electron microscopy?

A

The specimen must be coated with a thin find of heavy metal ex.gold

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23
Q

How magnified can a scanning electron microscope see?

A

15-100,000x

24
Q

What is the most powerful electron microscope?

A

Scanning Tunneling Microscopy

25
Q

What is a scanning tunnelling microscopy used to see?

A

Atoms

26
Q

How does a scanning tunnelling microscopy work?

A

Uses a thin metal probe to scan specimens revealing surface irregulations

27
Q

What must be used on the microorganism so that it is visible under a light microscope?

A

Stains

28
Q

Stains are composed of what?

A

Negatively and positively charged ions

29
Q

What is a chromophore?

A

The coloured negative or positive stain

30
Q

What are the steps of the staining procedure for microorganisms before being viewed under a light microscope

A
  1. Thin film called smear containing the microorganism is put onto slide
  2. Sample is fixed by passing through a flame
  3. Stain is applied to sample
  4. Stain is removed by rinsing
  5. The stain is now ready to be viewed
31
Q

The outer surface of bacteria has what type of charge?

A

Negative

32
Q

How does a positive stain work?

A

Positively charged stain adheres to negatively charged bacterium therefore bacteria is coloured and background is clear

33
Q

Whats an example of a positive stain?

A

Crystal violet

34
Q

How does a negative stain work?

A

It is repelled by the negatively charged bacteria therefore bacteria appears clear and background appears coloured

35
Q

What is an example of a negative stain?

A

Nigrosin (black)

36
Q

What are two types of staining techniques?

A

Simple stains and differential stains

37
Q

How does a simple stain work? What is sometime applied

A

Positively charged basic dye is applied therefore bacteria appears coloured, a mordant

38
Q

What is a mordant?

A

Something used to increase the intensity of a stain

39
Q

What is a differential stain used for?

A

To differentiate different types of bacteria because the stain react differently to different types of bacteria

40
Q

What does a differential stain use to its advantage to be able to tell between cells?

A

It exploits differences in cells wall structure and composition

41
Q

What are 2 examples of differential stains

A
  1. Gram stain

2. Acid Fast stain

42
Q

What is the gram stain used to determine?

A

Whether a bacterium is gram positive or negative

43
Q

When doing a gram stain, how can you tell which is gram negative and which is gram positive?

A

Gram postive- wil hold first purple stain

Gram negative- will not hold first stain but will hold second and appear pink

44
Q

What occurs in a gram stain?

A

Two stains are used with a wash in between

45
Q

Acid fast stains bind closely to..?

A

Bacteria that contain a waxy cell wall component

46
Q

What is an acid fast stain used to identify?

A

All bacteria that fall within the genus Mycobacterium

47
Q

What are two examples of Mycobacterium

A

Mycobacterium tuberculosis and Mycobacterium leprae

48
Q

What occurs in an acid fast stain?

A

The waxy cell wall retains the carbo fuschin die that is added (pink on blue), a counterstain methylene blue leaves tissues and non acid fast bacteria blue

49
Q

What are ‘special stains’ used for?

A

In order to visualize cell structures and specific parts of microorganisms

50
Q

What are 3 types of special stains

A
  1. Capsular stain
  2. Flagella stain
  3. Endospore stain
51
Q

What does a capsular stain do?

A

Reveals the presence of a thick polysaccharide layer outside the bacterial cell

52
Q

What does a capsule presence indicate?

A

A bacterium with increased ability to cause disease

53
Q

When doing a capsule stain, the background is coloured with what type of charged stain? The bacteria?

A

Negative (usually black), positive (pink)

54
Q

What does the capsule look like after being dyed?

A

Remains colourless and appears as a halo around the bacterium

55
Q

Why must special stains be used to detect the presence of endospores?

A

Ordinary stains cannot penetrate the bacterial cell wall

56
Q

What occurs in an endospore stain?

A

Primary stain colours endospore green

A counterstain with safranin colours the rest of the cell pink

57
Q

How does a flagella stain work?

A

The mordant and stain together work to increase the thickness of the flagella so it can be seen under a light microscope

Microbiology (16 decks)

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