Microscopy

    Cards (33)

    • What is the max magnification of a light microscope?
      x1500 (beyond this images become blurred)
    • What is the max resolution of a light microscope?

      200nm (0.2μm)
    • Light microscope facts:

      Limited magnification and resolution due to the use of light

      Can use live specimen

      Easy to prep and use

      Staining is required
    • Image from light microscope
    • What is the max magnification of an electron microscope?
      x500,000
    • What is the max resolution of an electron microscope?
      1nm
    • Electron microscope facts:

      Electron beams have a shorter wavelength than light

      The lower the wavelength the better the resolution (small resolution = clear image)

      Images are produced in B+W, colour is added after by a computer
    • Transmission Electron Microscope (TEM) facts

      Pass electrons through a specimen
      Shows structureswithinthe specimen
      Specimen must be thin and stained with heavy metals
      Stains are very dense and electrons can’t pass through them, which bounces them back.
      Specimen must be deadProduces 2D images
    • Why must the specimen be dead in TEM?

      heavy metals are toxic,
      the specimen has to be in a vacuum,
      put in resin and cut very thin
    • Image from transmission electron microscope
    • Scanning Electron Microscope (SEM) facts:

      Not as powerful magnification and resolution as TEM
      Only shows thesurfaceof a specimen
      Specimen’s coated with thin layer of metals - scatters electrons
      As electrons hit the surface they bounce back and are measured to produce a 3D image
      Produces 3D images
    • image from a scanning electron microscope
    • What is the definition of magnification?
      how much bigger an image appears compared to the original object
    • Why is electron microscopy important?

      It is vital in understanding cell structure and function

      It allows us to investigate organelle structures and roles within the cell, giving a greater understanding.
    • What is the definition of resolution?

      the ability to distinguish 2 points that are close together as separate points rather than a fused image
    • What is the formula for magnification?

      Magnification = image size / actual size
    • What is the stage micrometer?

      A millimeter long ruler etched onto a slide

      has 100 divisions, each of 0.01mm or 10 micrometers.

      It is used to calibrate the eyepiece graticule
    • What is an eyepiece graticule?

      a glass disc in the eyepiece lens that is marked with a fine scale from 1 to 100
    • How do you calibrate an eyepiece graticule?

      Place stage micrometer onto microscope

      Turn microscope onto lowest magnification (x4)

      Line up the stage micrometer and eyepiece graticule

      Find a point where they line up perfectly

      If the stage micrometer is 1mm, each small division is 0.01mm or 100micrometers

      Each line on the eyepiece graticule is 1 EPU - so every big line is 10 EPU
    • microscope image labelled
    • What is cell fractionation?
      The process where cells are broken up and organelles are separated so their individual functions can be studied
    • Why must cell fractionation be gentle?

      The process used to separate organelles must be gentle in order to keep them in tact so they still function
    • What is the order of processes in cell fractionation?

      Homogenisation,
      Centrifugation,
      Differential centrifugation
    • What is homogenisation?

      Disruption of cells

      It is carried out in a buffered, isotonic and ice cold solution in a blender called a homogeniser

      This results in a thick 'soup' called homogenate
    • Why does the solution in homogenisation need to be isotonic?

      To maintain water potential of the cell, eg prevents water from moving in/out to stop any damage.
    • Why does the solution in homogenisation need to be ice cold?
      To prevent further enzyme action which modify organelles
    • Why does the solution in homogenisation need to be buffered?
      It prevents a change in PH
    • What is centrifugation?

      The process where components are separated based in size and density
    • What happens in centrifugation?

      The suspension is spun in a centrifuge at a specific speed
      Larger, densecomponents are pulled to the bottom of the tube to form asediment
      Smaller, less densecomponents remain in the suspension (called thesupernatant)
    • What happens in differential centrifugation?
      The supernatant is spun again at higher speed so another organelle forms the sediment

      After each spin the supernatant is poured out and spun again at a different speed

      This process is repeated, each time at a faster speed

      At the end, supernatant fluid only contains soluble proteins which can be separated by electrophoresis.
    • Cell
      Microscopic mass of cytoplasm enclosed in a membrane and is the smallest structural and functional unit of an organism
    • Cell
      • Provides structure to the body by combining into tissues, organs and organ systems
      • Absorb nutrients
      • Excrete waste
      • Respiration occurs within cells
      • Transport
    • Cell types

      • Archaea (Prokaryote)
      • Bacteria (Prokaryote)
      • Eukaryotes
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