Ppt 1

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Ppt 1
2011-10-12 18:39:44

Midterm 1
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  1. light microscopy
    resolves images of individual bacteria based on their absorption of light.
  2. example of light microscopy.
    bright field, dark field, phase contrast, fluorescence
  3. electron microscopy
    use beams of electrons to resolve details several orders of magnitude smaller than those seen under light micrscopy
  4. examples of electron microscopy
    SEM, TEM,
  5. AFM - atomic force microscopy
    use van der waals forces between a probe and object to map the 3d topography of cell
  6. Xray crystallography
    detect interference pattern of xrays entering the crystal lattice of molecule
  7. 3 conditions to resolve an oject using electromagnetic radition
    • 1. contrast between object and its medium
    • 2. wa velength smaller than object
    • 3. a detector with sufficient resolution for the given wavelength
  8. Prokaryotes are...
    Bacteria and Archaea
  9. absorption
    photon's energy is acquired by the absorbing object
  10. relfection
    wave front bounces off the surface of an object
  11. refraction
    bending of light as it enters a substance that slows its speed
  12. scattering
    when wave front interacts with an object smaller than wavelength of light
  13. wave fronts of light shift direction as...
    as they enter a substance of a higher refractive index
  14. parabolic lenses
    light rays are brought to a focal point
  15. increase resolution (how)
    • 1) use shorter wavelength light
    • 2. lessen contrast
    • 3. use of immersion oil
    • 4. use of wider lens closer to specimen
  16. superimpose refracted light and transmitted light shifted out of phase
    phase - contrast microscopy
  17. reveals differences in refractive index as patterns of light and dark
    phase-contrast microscopy
  18. use to view live cells and cellular ogranelles
    phase contrast microscopy
  19. fluorescence microscopy
    incident light is absorbed by the specimen and re-emitted at a lower energy, thus longer wavelength
  20. Confocal laser scanning microscopy
    • both excitation light and emitted lights are focused together.
    • -visualize cells in 3d
    • -allows observation of live microbes in real time
  21. TEM
    Electrons pass thru the specimen and reveals internal structures
  22. SEM
    Electrons scan the specimen surface and reveals external features in 3D
  23. microtome
    cuts slices thru specimen in EM
  24. electron cryomicroscopy
    • aka cryo-electron microscopy (cryo-EM)
    • specimen is flash-frozen (suspended in water and frozen rapidly
  25. cryo-electron tomography/electron cryotomography
    • avoids need to physically slice sample for thin section TEM
    • -generate high resolution model of cirus particles
  26. AFM
    measures the van der Waals forces between electron shells of adjacent atoms of the cell surface and the sharp tip
  27. SPM
    Scanning probe microscopes; enable nanoscale observation of cell surfaces, including living cells suspended in water