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MCB 11 LEC > Module 2 > Flashcards

Module 2 Flashcards

1
Q

1 micrometer (μm) =

A

10^-6 m

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2
Q

1 nanometer (nm) =

A

10^-9 m

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3
Q

What makes a good microscope

A

adequate magnifying power
high resolving power
serves your purpose
provides good contrast

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4
Q

two main types of microscopes

A

light and electron

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5
Q

microscope that use light waves and mirrors

A

light microscopes

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6
Q

types of light microscopes

A

simple, compound/complex, bright-field, dark-field, phase contrast, differential interference contrast, fluorescence, confocal, two-photon

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7
Q
  • use electron beams as energy source
  • has higher magnification and resolving power
  • for objects smaller than 0.2 mm in diameter
  • in vacuum
  • should have mo water when used
A

electron microscope

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8
Q
  • objects under study are darker
  • microscopic field is brightly lit
  • gross morphology
  • can be used stained or unstained
A

BRIGHT FIELD

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9
Q
  • microscopic field is dark
  • objects under study are luminous
  • for specimens that are:
    • invisible in the ordinary light microscope
    • cannot be stained by standard methods
    • distorted by staining
  • has opaque disc that blocks light
A

DARK FIELD

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10
Q
  • principle is based on variations in the refractive indices
    (measure of bending or refracting of a beam of light on
    entering a denser medium)
  • not necessary to fix or stain cells
  • detailed examination of internal structure
A

PHASE CONTRAST

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11
Q
  • principle is based on variations in the refractive indices
  • advantage: no diffraction halo associated with phase contrast
  • disadvantage: the three-dimensional appearance may not represent reality
A

DIFFERENTIAL INTERFERENCE CONTRAST

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12
Q
  • makes use of fluorochromes
  • visualizes specimens that fluoresce
  • detection of immunological reactions
  • can be direct (primary antibody fluorochromes) and indirect (secondary antibody is attached to primary antibody)
A

FLUORESCENCE

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13
Q
  • useful for thick specimens like biofilms
  • used to visualize structures
A

CONFOCAL

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14
Q
  • useful for examining living cells within intact tissues
  • currently limited to advanced clinical and research laboratories
A

TWO-PHOTON

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15
Q

types of electron microscopes

A

TRANSMISSION ELECTRON MICROSCOPE (TEM),
SCANNING ELECTRON MICROSCOPE (SEM),
SCANNING TUNNELING MICROSCOPE (STM),
ATOMIC FORCE MICROSCOPE (AFM)

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16
Q
  • ultrastructure in thin section of the cells
  • can project images in a much higher resolution—up to the
    atomic level of thinner objects
  • examine viruses
  • cells should be killed
  • 100,000 X and above magnification
A

TRANSMISSION ELECTRON MICROSCOPE (TEM)

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17
Q
  • surface features of viruses and cells
  • reveals a 3-D image
A

SCANNING ELECTRON MICROSCOPE (SEM)

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18
Q

for observing materials like Pure Gold Surface

A

SCANNING TUNNELING MICROSCOPE (STM)

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19
Q

for observing Nanocellulose

A

ATOMIC FORCE MICROSCOPE (AFM)

20
Q

advantages of examining organisms in living or natural state

A
  • observation of unaltered/undistorted characteristics
  • cellular processes can be studied
  • motility can be observed
  • simple to prepare
21
Q

disadvantages of examining organisms in living or natural state

A
  • refractive index of cells almost similar to that of water
22
Q

advantages of examining organisms in stained organisms

A
  • provides contrast
  • slides can be preserved
  • specimens are killed
23
Q

disadvantages of examining organisms in stained organisms

A
  • more complicated and tedious to prepare
  • expensive
24
Q

Three basic steps in staining microorganisms:

A
  1. Smear Preparation
  2. Fixation
  3. Staining
25
Q

a thin, dry film of microorganisms

A

Smear

26
Q

STEP 1: Smear Preparation

A

spread culture in thin film over slide -> dry in air

27
Q

purpose of fixation

A
  • kills the cells
  • makes the cells sticky
  • increases apparent diameter of cells
28
Q

types of fixation

A
  1. Heat Fixation
  2. Chemical Fixation
29
Q
  • fixation through direct flame or steam
A

Heat Fixation

30
Q
  • fixation using alcohols
A

Chemical Fixation

31
Q
  • application of biological dyes
A

Staining

32
Q
  • organic compounds carrying chromophoric ions
  • make cell’s internal and external structures more visible with the increased contrast with the background
A

Dyes (Stains)

33
Q

Types of Stains:

A
  1. Basic or Positively-Charged Dye
  2. Acidic or Negatively-Charged Dye
  3. Neutral
34
Q

staining which only uses one dye

A

SIMPLE STAINING

35
Q

types of simple staining

A

Positive / Direct
Negative / Indirect

36
Q
  • cells are the same color as the dye
  • crystal violet, malachite green, methylene blue, safranin
A

Positive / Direct

37
Q
  • cells are colorless or luminous
  • acid fuchsin, eosin, rose bengal, india ink, nigrosin
A

Negative / Indirect

38
Q
  • two or more dyes and/or reagents are used
A

DIFFERENTIAL STAINING

39
Q

examples of DIFFERENTIAL STAINING

A

Gram Staining
Acid-Fast Staining

40
Q
  • used in finding gram-positive / gram-negative
A

Gram Staining

41
Q
  • used in diagnosis of tuberculosis
A

Acid-Fast Staining

42
Q

Gram staining process

A

1: crystal violet (primary stain) -> stain cells turn purple or blue
2: iodine (mordant makes dye less soluble so it adheres to cell walls) -> cells remain blue or purple
3: alcohol (decolorizer washes away stain from gram-negative cell wall) -> gram positive remains the same color, gram negative turns colorless
4: safranin (counterstain allows dye adherence to gram-negative cells) -> gram positive remains the same color, gram negative turns pink/ red

43
Q

methods used in Acid-Fast Staining

A
  • Ziehl-Neelsen Technique
  • Kinyoun Technique
44
Q

types of staining

A

simple staining
differential staining
structural staining

45
Q
  • two or more dyes and/or reagents to emphasize structures
A

STRUCTURAL STAINING

46
Q

structural staining is used for:

A
  • Capsules
  • Endospores
  • Flagella
  • Storage Granules

MCB 11 LEC (6 decks)

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