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CBE 2290 > Module 2 > Flashcards

Module 2 Flashcards

1
Q

What is the goal of a microscope?

A

to accurately enlarge or magnify the image of an object

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2
Q

What is light refraction?

A

when light passes from one medium to another, it is refracted or bent, at the interface

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3
Q

What is the refractive index?

A

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

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4
Q

what focal length will magnify an object more?

A

a lens with a shorter focal length

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5
Q

what focal length will magnify an object less?

A

a lens with a longer focal length

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6
Q

What is microscope resolution?

A

the ability of a lens to separate or distinguish small objects that are close together

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7
Q

What is the objective lens?

A

the lens closest to the specimen

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8
Q

What is the Abbe Equation?

A

d = 0.5λ/nsinΘ

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9
Q

what is the d in the Abbe Equation?

A

min. distance between 2 objects to distinguish them

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10
Q

what is the nsinΘ in the Abbe Equation?

A

numerical aperture (NA, ability to gather light)
n = refractive index of medium
Θ = amount of light entering the lens

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11
Q

How can we get the best resolution using Abbe’s Equation?

A

want the smallest d
- small λ
- large nsinΘ

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12
Q

What is a light microscope?

A

compound microscopes, where the image is enlarged by the action of 2 or more lenses

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13
Q

what are the 2 parts of the 2 lens system

A
  1. Objective
  2. Eye-piece
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14
Q

Explain the Objective part of the 2 lens system

A
  • nearer the specimen
  • magnifies the specimen
  • shorter the focal length, shorter the working distance
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15
Q

Explain the Eye-piece part of the 2 lens system.

A
  • eye-piece is the ocular
  • produces virtual image seen by the eye
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16
Q

How do you find the Total Magnification using a light microscope?

A

ocular magnification * objective magnification

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17
Q

What is fixing in sample preparation?

A

fixing preserves internal and external structures (organisms killed and firmly attached to microscope slides)

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18
Q

What are the two types of fixation in sample preparation?

A
  1. heat fixation
  2. chemical fixation
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19
Q

When is heat fixation used?

A

routinely used with prokaryotes; preserves overall morphology but not internal structures

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20
Q

When is chemical fixation used?

A

used with larger, more delicate organisms; protects fine cellular structures + morphology

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21
Q

What is staining in sample preparation?

A
  • staining increases visibility and accentuates specific morphological features
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22
Q

What are the two common features of dyes in staining?

A
  1. Chromophore groups (chemical groups with conjugated double bonds that give color)
  2. Ability to bind with cells (ionic, covalent, hydrophobic bonding)
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23
Q

Explain simple staining

A
  • a single stain is used
  • useful for determining size shape and arrangement of cells
  • most common with binding by ionic interactions
24
Q

What do basic dyes bind to?

A

negatively charged molecules (DNA, proteins, cell surfaces)

25
Q

What do acidic dyes bind to?

A

positively charged molecules

26
Q

What is differential staining?

A

differential staining is used to differentiate organisms based on their staining properties

27
Q

What type of staining is gram staining?

A

differential staining

28
Q

What is gram staining?

A

the most widely used differential stain that differentiates based on differences in the cell wall structure

29
Q

Gram (+) gives a _______ colour

A

dark purple

30
Q

Gram (-) gives a ________ colour

A

pink/red

31
Q

What is a brightfield microscope?

A

produces a dark image against a bright background

32
Q

What can a brightfield microscope observe?

A
  • viewing organizations of microorganisms
  • stained bacterial cells (ex. gram staining)
33
Q

What does a darkfield microscope show?

A

produces a bright image against a dark background

34
Q

What is a darkfield microscope used for?

A
  • used to observe living, unstained preparations (bacteria, algae)
  • used to observe internal structures in eukaryotes
  • thin, delicate samples
35
Q

What is a phase contrast microscope?

A

enhances contrast in transparent/colorless samples by amplifying small differences in the refractive index of the sample

36
Q

What can a phase contrast microscope observe?

A
  • excellent way to observe living cells (esp. eukaryotes)
  • can view cell division (mitosis and meiosis) without needing to kill or stain
37
Q

What is a fluorescence microscope?

A

microscope that uses fluorescent dyes (fluorochromes) to label specific structures in a sample

38
Q

What can a fluorescence microscope observe?

A
  • protein localization
  • tracking live cells over time
  • studying cell organelles
39
Q

How are images produced in electron microscopy?

A

by beams of electrons

40
Q

What is different about the wavelength in electron beam vs light?

A

the wavelength is much shorter with the electron beam

41
Q

What are the advantages to a shorter wavelength in electron microscopy?

A
  • significantly higher resolution
  • useful for different studies of microorganisms
42
Q

What is a TEM?

A

transmission electron microscopy:
- the electrons that don’t scatter when passing through a specimen are transmitted and used to produce an image

43
Q

What happens in the denser regions of a TEM?

A

the denser regions scatter more electrons and appear darker

44
Q

What can a TEM observe?

A

produces images of internal structures

45
Q

What is a SEM?

A

Scanning Electron Microscopy:
- uses a focused beam of electrons reflected from the surface to create an image

46
Q

What can a SEM observe?

A

produces a 3-D image of the surface of a cell/sample

47
Q

What must be done to the sample before observing in an electron microscope?

A

samples must be fixed, dried and coated in metal
(therefore, they must be dead)

48
Q

What is a confocal microscope?

A

scanning laser microscope that creates high resolution, 3-D images of the species

49
Q

What can a confocal microscope observe?

A
  • live, 3-D cell imaging is possible
50
Q

What study is a confocal microscope used for?

A

useful for the study of biofilms.

51
Q

What are the two types of scanning probe microscopy?

A
  1. Scanning tunneling microscope
  2. Atomic force microscope
52
Q

What is Scanning tunneling microscope?

A

sharp probe moves over the surface of a specimen at a constant current to create an image

53
Q

What does a scanning tunneling microscope show?

A

allows scientists to view atoms on the surface of a solid

54
Q

What is an atomic force microscope?

A

sharp probe moves over surface of specimen at a constant distance to produce an image

55
Q

What does an atomic force microscope show?

A

used to study the interaction of pr-, to follow the behavior of living bacteria + other cell, and to visualize membrane pr- such as aquaporins

56
Q

What do Scanning Probe Microscopes use to create images of samples?

A

they use mechanical interactions between the probe and sample surface to gather info

CBE 2290 (12 decks)

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