Microscopes - created from Mind Map

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1. Light

2. Electron (1933)

can magnify 400X (max) in schools

resolving power of 0.4 to 0.2 um

view living or dead cells

focused by glass lenses

Greater ability to observe + magnify --> because wavelength of electrons are smaller than the wavelength of visible light

CELLULAR AND SUB-CELLULAR LEVEL: view small molecules, viruses and organelles that light microscopes cannot detect

images are produced using a beam of electrons made to behave like light waves

Types:

Disadvantages

Techniques for preparing specimen:

can be hooked up with computers to digitally enhance images

TRANSMISSION ELECTRON MICROSCOPE (electrons transmitted)

SCANNING ELECTRON MICROSCOPE (electrons bounced off)

electrons must pass in a vacuum

only processes non-living and preserved tissues

projected onto a photographic plate

focused by electron magnets

causes specimen to emit its own electrons, therefore making a 3D image

1955

however low resolution

Size = one small room

constant temperature and pressure

expensive - therefore not always accessible

1. FIXATION; tissue placed in preservative substance that kills it and preserves it, as closely to living state as possible

2. EMBEDDING; tissue embedded in hard medium (eg. wax, resin) to make it easier to cut small pieces

3. SLICING: using microtome, sliced very smoothly and thin

4. STAINING; stained using coloured dye to create a contrast between transparent material and its background