AS LEVEL- Biology- Basic components of living systems (Microscopes 2)

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  • Electron microscope
    • Basic components of living systems (Microscopes 2)
      • Lazer Scanning Confocal microscope
        • Uses lazer beams to scan a specimen which is usually tagged with a fluorescent dye
        • The lazer causes the dye to give off light. This light is then focused through a pinhole onto a detector. The detector is hooked up to a computer which generates an image
        • The image produced can be 3D
        • They can be used to look at objects at different depths in thick specimens
        • The pinhole means that any out-of- focus light is blocked, so the image produced is more clearer than a normal light microscope
    • Preparation
      • Fixing- Using chemicals to preserve to prevent decomposition
      • Dehydration- Removes water + prevents vapourisation in the vaccum which would damage the specimen
      • Staining with heavy metals- Metals are used to create contrast in the electron beams
    • 2 types; TER + SER
      • Transmission Electron Microscope (TEM)
        • Smaller organelles can be seen eg. ribosomes , RER
        • Cost =  Expensive
        • Size = Big
        • Sample preparation =  Complex
        • Dead or Alive? Dead
        • Vacuum? Yes
        • Colour of specimen =  Black + white
        • Magnification = Over x500,000
        • Resolution = 3-10nm
      • Scanning Electron Microscope (SEM)
        • Size = Big
        • 3D image is produced + surface detail can be seen
        • Resolution = 3-10nm
        • Magnification = Over x500,000
        • Colour of specimen =  Black + white
        • Vacuum? Yes
        • Dead or Alive? Dead
        • Sample preparation = Complex
        • Cost = Expensive


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