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Biology Module 2 > 1. Microscopy > Flashcards

1. Microscopy Flashcards

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1
Q

Biological drawing checklist

A

sharp pencil
• take up at least half the page
• lines need to be clear and continuous (no shading/colouring)
• label lines in pencil
• label lines touch the actual part your labelling
• label lines don’t cross over each other
• ensure proportions are correct
• label all areas that you have shown
• no arrow heads
• LOW POWER TISSUE PLAN

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2
Q

Define magnification

A

How many times bigger image size is than actual size of a specimen

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3
Q

Define resolution

A

The ability to distinguish between two points in an image - detail

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4
Q

Resolution of light microscope

A

200nm

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5
Q

What does it mean if something is closer together than 200m on a light microscope

A

They will be seen as one object

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6
Q

Max magnification of a light microscope

A

1500x

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7
Q

Type of samples for a light microscope

A

Thin, transparent samples
Living or dead

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8
Q

What stains DNA

A

Acetic Orcein

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9
Q

What colour does acetic orcein stain dna

A

Dark red

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10
Q

Why may some samples be sectioned (embedded in wax)

A

To help preserve the structure while cutting

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11
Q

How does a light microscope work

A

Has two convex glass lenses: objective (near specimen) and eyepiece lens.
Mirror/light source directs light through condenser (focuses light), diaphragm and through sample.
Image is magnified by the objective lens (usually 4x, 10x or 40x).

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12
Q

Pros of light microscopes

A

• Inexpensive to buy and operate
• Small and portable
• Sample preparation does not usually lead to distortion
• Vacuum not required
• Natural colour is seen - unless stained
• Specimens can be living or dead

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13
Q

Cons of light microscope

A

Lower magnification
• Lower resolution
• Bubbles in cover slips - artefacts

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14
Q

What are artefacts

A

damage caused in specimen preparation

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15
Q

Resolution of TEM

A

0.02nm

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16
Q

Resolution of SEM

A

0.2 nm

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17
Q

Resolution of LSCM

A

200nm

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18
Q

Magnification of SEM

A

X100,000

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19
Q

Magnification of TEM

A

× 500,000

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20
Q

Magnification of LSCM

A

× 2000

21
Q

SEM and TEM samples

A

dead
•dries and coated with heavy metals

22
Q

Why do electron microscope samples need to be coated with heavy metals

A

to increase the level of contrast in the final image.

23
Q

Types of samples in LSCM

A

Different layers at different depths
Living or dead

24
Q

How does TEM work

A

A beam of electrons is passed through a vacuum to ensure electrons are traveling in a straight line,

with a wavelength less than 1mm is transmitted through the specimen and focused to produce and image.

25
Q

How does an SEM work

A

A beam of electrons is sent across the surface of a specimen and the reflected electrons are collected

26
Q

Pros of TEM

A

High magnification
• High resolution

27
Q

TEM cons

A

Specimen must be fixed in plastic
• Must be dead
• Expensive
• Complex sample preparation
• Vacuum required
• Sample preparation often distorts image
• Black and white images produced - but can be coloured digitally

28
Q

SEM pros

A

They can be used on thick or 3-D specimens
• They allow the external, 3-D structure of specimens to be observed

29
Q

SEM cons

A

Lower resolution than TEMS
• Samples must be dead
• They don’t produce a colour image

30
Q

How does an LSCM work

A

Uses lasers
• Cells are stained with a fluorescent dye
• A thick section of tissue, or a living organism, can then be scanned with a laser beam which can be reflected by the dyes
• The laser beam is scanned at different depths

31
Q

LSCM advantages

A
  • can be used on thick or 3d specimens
  • allow external, 3d structure to be observed
  • depth selectivity + very clear images produced
32
Q

LSCM uses

A

A use in optometry
Eg. Looking at scratches in the cornea

33
Q

What does the pinhole do in LSCM

A

Prevents scattered light from being detected - would blur the image

34
Q

What type of microscope produces these

A

TEM
- can see Golgi apparatus + mitochondria

35
Q

What type of microscope produced these

A

SEM

36
Q

What do the magnets do in an electron microscope

A

The condenser lenses are magnets which can focus and direct the electron beam

37
Q

Dry mount

A

Solid specimens are viewed whole or cut into thin slices (sectioning).
• Specimen placed on centre of slide, cover slip ontop

38
Q

Dry mount examples

A

dust, insect parts -whole, muscle tissue or plants - sectioned.

39
Q

Wet mount

A

Specimens suspended in liquid (water or immersion oil). Cover slip placed at angle, aquatic samples and other living organisms viewed.

40
Q

Purpose of stains

A
  • contrast is higher
  • more structures visible
  • clearer image obtained
41
Q

Differential staining

A

Makes cells + structures visible/ distinguish between components
Increase contrast
Identify differences between cells and identify differences between organelles

42
Q

Types of staining techniques

A

Gram stain + acid fast technique

43
Q

How to calculate the length of a sample

A
  • use eyepiece graticule + calibrate using stage micrometer
  • measure diameter of sample in graticule units
  • take repeat measurements + calculate mean length
  • use calibrated epu to calculate length
44
Q

How to improve on sample taking

A

Sharp blade = slide thin enough that individual cells are visible
Wet mount = prevents dehydration
Squash slide = easier to see individual cells

45
Q
A
46
Q
A
47
Q

2nd part - Using Fig. 2, and the information provided, suggest and explain why the cytoplasm of cell C and cell
D reacted differently to the stain.

A
48
Q
A
49
Q

If a question asks you to draw cells based of a microscope image what do you usually need to include

A

Biology Module 2 (11 decks)

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