M1:T3: Microscopy

• what are the 2 ways to view organisms

  1. light microscopy
  2. electron microscopy
• light microscopy

  • routine viewing
  • micrometer size
  • uses light
  • low resolution
  • no magnification
• types of light microscopy

  1. bright field: direct light source, bacteria lack constfast
  2. dark field: background is black and only light scatters by specimen
  3. phase contrast: improves contrast between cells and surrounding, splits light into 2 beams
  4. fluorescence: uses UV light source, absorbs at low W and emits at high W <— made by dyes
• magnification occurs in … in light microscopy

  1. line of vision
  2. objective lens
• electron microscopy

  • used for the study of cellular structure details and viruses
  • high magnification and resolution “0.2nm”
  • uses electrons, shorter wavelengths
• types of electron microscopy

  1. TEM: transmission electron microscope: electrons pass through objects, can see internal structure but hard to see contrast
  2. SEM: scanning electron microscope: external structure
• 3 ways to improve resolution

  1. shorter wavelength
  2. increase numerical aperture
  3. oil immersion lens
• 3 types of Stains

  1. simple stain: cationic and anonic dyes
  2. gram stain: purple and pink
  3. acid-fast stain: red lipid layer