Electron Microscopy Flashcards
2 types of electron microscopy
- transmission
2. scanning
transmission electron microscope
beam of electrons passes through specimen revealing 2D image
why is it called “transmission”
because electrons may pass through the specimen
what is typically viewed through a TEM
very small parts of cells
scanning electron microscope
beams of electrons bounce off a specimen revealing a 3D image
what are the light regions in a SEM image
where electrons bounce back to the detector
what is SEM used for typically
whole cells and other larger things
how do you prepare a specimen for SEM
sputter coat with metal atoms
5 preparation methods for TEM
- ultrathin sectioning and metal atom staining
- ultrathin sectioning and gold-labelled antibodies
- negative staining
- shadowing
- freeze-fracturing and shadowing
ultrathin sectioning
specimen is sectioned with an ultramicrotome
ultrathin sectioning thickness
less than 100 nm
gold-labelled antibodies
antibodies with gold beads are attached to proteins in a cell
what is negative staining used for viewing?
extremely small objects like viruses
how does negative staining work
specimens are highlighted against an electron dense background
negative staining procedure
- soak everything in a solution with metal atoms
- draw away fluid and atoms collect near specimen
