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Biology Module 2 > Microscopy > Flashcards

Microscopy Flashcards

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1
Q

What are the 4 types of microscope?

A
  • Light microscope
  • Scanning Electron microscope (SEM)
  • Transmission Electron microscope (TEM)
  • Laser Scanning Confocal microscope
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2
Q

How does a light microscope work?

A

It uses light and a series of glass lenses to form a magnified image, limiting it’s resolution.

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3
Q

What are the advantages of using a light microscope?

A
  • Relatively cheap
  • Easy to set up and use
  • Can be used to view eukaryotic cells, nuclei and sometimes mitochondria and chloroplasts
  • Cells can be viewed in colour
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4
Q

What are the disadvantages of using a light microscope?

A
  • They have a maximum resolution of around 0.2 micrometres / 200 nm
  • Cannot be used to observe ribosomes, ER or lysosomes
  • Maximum magnification is usually on x1500
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5
Q

How does an SEM microscope work?

A

A beam of electrons is scanned ACROSS the specimen’s surface. The electrons bounce off the specimen and are detected, forming a 3D image.

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6
Q

What are the advantages of using an SEM microscope?

A
  • Can be used on thick, 3D specimens
  • External 3D structures can be observed
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7
Q

What are the disadvantages of using an SEM microscope?

A
  • Lower resolution than TEMs
  • Cannot view live specimens
  • Colour images are not produced. Images are also digitally processed
  • Lower magnification than TEMs (around x500,000)
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8
Q

How does a TEM microscope work?

A

Electromagnets are used to focus a beam of electrons which is transmitted THROUGH the specimen. Denser parts of the specimen absorb more electrons and appear darker. Specimens require lengthy treatment and artefacts can be introduced.

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9
Q

What are artefacts?

A

A structural feature which is not part of the actual specimen, and instead produced in preparing the specimen (e.g. an air bubble).

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10
Q

What are the advantages of using a TEM microscope?

A
  • Magnification = x1,000,000 or higher
  • Internal cell structures can be seen
  • High resolution imagery (more detail).
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11
Q

What are the disadvantages of using a TEM microscope?

A
  • Only thin specimens / sections of an object can be used
  • No live specimens as a TEM uses a vacuum
  • 2D, no colour
  • All water must be removed from the specimen
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12
Q

Why do electron microscopes increase resolution?

A

A beam of electrons has a shorter wavelength than a beam of light. The max resolution of an electron microscope is around 0.2 nm or 0.0002 micrometres.

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13
Q

How do Laser Scanning Confocal microscopes work?

A

Cells are stained with fluorescent dyes and a section of tissue is scanned with a thick laser beam (focused light). The light is reflected by the dyes. Multiple depths are scanned to produce an image.

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14
Q

What are the advantages of using a Laser Scanning Confocal microscope?

A
  • Can be used on thick, 3D specimens
  • External 3D structures are observed
  • Very clear resolution as laser beam can be focused at a very specific depth (cytoskeleton can be viewed)
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15
Q

What are the disadvantages of using a Laser Scanning Confocal microscope?

A
  • Slow process and long time to obtain cell image
  • Laser beam can cause photodamage to the cell
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16
Q

What is meant by magnification?

A

How many times bigger the image produced is than the real life object.

17
Q

What is meant by resolution?

A

The ability to distinguish between two objects that are very close together.

18
Q

What is the standard form of micro and nanometres?

A

Micro = 10^-6 metres
Nano = 10^-9 metres

19
Q

How is total magnification calculated?

A

eyepiece lens magnification x objective lens magnification

20
Q

How is magnification calculated?

A

image size / actual size

21
Q

How is magnification increased?

A

By using a higher powered objective lens.

22
Q

What is an eyepiece graticule and stage micrometer used for?

A

Measuring an object’s size when viewing it under a microscope.

It needs to be calibrated each time a different magnification is used.

23
Q

What is an eyepiece graticule?

A

A disc placed in the eyepiece of the microscope which has 100 divisions and no scale.

24
Q

What is a stage micrometer?

A

A slide placed onto the stage which has a very accurate scale in micrometers.

25
Q

How do you calculate the size of 1 graticule division?

A

1 graticule division = number of micrometers / number of graticule divisions.

26
Q

How can graticule divisions be used to calculate the object size?

A

measurement (in micrometers) = graticule divisions x magnification factor

27
Q

What is the definition of a photomicrograph?

A

A photo or digital image taken through a microscope to show a magnified image of a specimen.

Biology Module 2 (8 decks)

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