Cell structure- Microscopy

  • Created by: gsemma
  • Created on: 10-01-19 09:14
View mindmap
  • Microscopy
    • types
      • light/optical
        • produces a colour 2D image
          • max. mag= x1,500
            • res= 200nm
        • light shines through to give an image through the lens.
          • Inexpensive, portable, living sample, min. training
            • low mag and res due to longer wavelengths and samples need staining to show organelle
      • Scanning
        • produces a B&W 3D image
          • max mag= x200,000
            • res= 0.1nm
        • beam of electrons fired at sample and some are knocked off; these are detected to create the image.
          • forms complex 3D images and mag and res is higher than light microscope.
            • large and expensive, lots of training needed, specimen is dead and mounted in vacuum
      • Transmission
        • produces a B&W 2D image
          • max. mag= x2,000,000
            • res= 0.1nm
        • uses electromagnets to transmit an electron beam through the specimen. denser parts absorb more so show up darker giving texture.
          • highest mag and res of any microscope
            • large, expensive, dead specimen, stains potential hazardous, mount in vacuum
    • magnification (mag)
      • how much bigger the image appears through the lens compared to the naked eye
      • the shorter the wavelength the higher the mag
    • resolution (res)
      • the clarity of the image- the ability for the instrument to distinguish between two points that are close together.
    • Magnification= image size/ object size
    • graticule calculations
      • scales that are placed in a microscope and are used to measure the size of a specimen. An eye graticule must be calibrated before use.
        • eye
          • placed in eyepiece. no defined scale
        • stage
          • placed on the stage. Has a defined scale
            • calculate size- compare the EPG to the SG units
              • placed in eyepiece. no defined scale
    • cell fractionation
      • process of separating the organelles from the cell.
        • 1. preparation of cell to protect organelle- isotonic ( same water pot. to prevent shrinking and lysis), buffered (maintain pH), and cold (reduce enzyme activity).
          • 2. homogenisation- blend the sample to release organelle then filter the homogenate to remove any debris
            • 3. ultracentrifugation- homogenate spun at different speeds to extract organelle. heaviest fall to bottom and supernatum is poured off and spun again.
              • organelle fall in this order- naught clever monkeys like eating red raspberries- nucleus, chloroplasts, mitochondria, lysosomes, endoplasmic rectilium, ribosomes.


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes and structure resources »