Microscopy

• Optical

  first sort to be used

  used in school, colleges and research laboratories because they are:

  pros : cons :

  relatively cheap up to x2000

  able to study Living cells 200 nm resolution

  easy to use and portable
• optical microscope

  • lenses focus rays of light and magnify the view of the thin piece or specimen
  • different structures absorb different amount and wavelengths of light

  reflected light is transmitted to the observer via the eyepiece and objective lenses
• Laser scanning confocal

  uses a laser beam of light to illuminate chemical stains within specimen + then fluoresce

  • used in medical research

  fluorophores emit photons

  Photomultiplier tube amplifies the signal onto a detector

  pros : cons:

  living cells more expensive than light

  higher resolution than light more complex than light

  can observe cell processes by

  tracking molecules
• Transmission EM

  uses focused electron beam through sections of tissues

  more dense structures appear darker as they absorb many electrons

  focus images onto fluorescent screen or photomicrograph plate using magnetic lenses

  2D black n white
• Transmission EM

  pros : cons:

  up to x500,000 dead cells only

  can see detail inside cells harsh chemicals during prep

  0.5 nm which can cause artefact

  need skill to use

  expensive
• Scanning EM

  focused electron beam on to specimen's surface using electromagnetic lenses

  reflected electron hit off a collecting device and are amplified to produce an image on a photographic plate

  3D greyscale
• Scanning EM

  pros : cons:

  up to x500000 only dead cells

  3-10nm harmful chemicals used in

  can see details of structure's surfaces prep which can cause

  artefacts

  expensive
• how to prepare a wet temporary mount of tissue

  O- obtain a thin piece of specimen

  A-add a drop of water

  S- Stain tissue on slide to make structure more visible

  C-add a coverslip using mounted needle at 45° to avoid air bubbles