analysis of cell components

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  • analysis of cell components
    • optical (light) microscopes
      • use light to form an image
      • have a maximum resolution of 0.2Mm
        • can't see ribosomes, endoplasmic reticulum or lysosomes
      • maximum magnificationof x1500
    • electron microscopes
      • use e- to form an image
      • higher resolution than optical microscopes so give a more detailed image
        • maximum resolution of 0.0002Mm
      • maximum useful magnifications x1500000
      • transmission electron microscope (TEMs)
        • use electromagnets
        • denser parts absorb more e- so look darker
        • only used on thin specimens
        • flat and 2D
      • Scanning electron microscope (SEMs)
        • beam e- across specimen
          • this knocks off e- from the specimen which are gathered in a cathode ray tube to form an image
        • surface of specimen, 3D
        • lower resolution than TEMs
    • magnification=image size/object size
      • image= appearance on microscope
    • cell fractionation
      • 1. get a sample of tissue the same concentrationas inside the cells
        • isotonic solution
          • stops osmosis so organelles don't burst
        • ice cold to stop enzyme activity
        • buffer to stop pH changes
        • 2. grind tissue in blender to break up cells
          • homogenisation - a sample with all contents distributed evenly
          • 3. fileter to remove insoluble tissue e.g. cel wall
            • 4. centrifuge sample
              • spin at low speeds and gradually get faster
                • low speeds = heaviest organelles in pellet
                  • Untitled
                • re-spin supernatant


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