BIOL 2021 Lecture Notes - Lecture 13: Transmission Electron Microscopy, Scanning Electron Microscope, Electron Microscope
19 Jan 2018
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Document Summary
Transmission em: uses an electron gun to shoot electrons at the specimen of interest. Specimen must be in thin slices so that electrons can travel through it and must be placed in a vacuum. Electrons travel through the specimen and an image is seen on a screen or digital camera. Must be stained with electron-dense material (heavy metals) so that they can absorb/block the electrons. Electrons pass through the specimen and the stained areas will look dark since no electrons pass through. An electron microscope is used to resolve objects smaller than light microscopes can (1nm) Wavelength of electrons is shorter than light. Light microscopes can observe living or dead cells, and stained cells. Electron microscopes can only be used for dead cells because of an elaborate preparation. Can get down to the molecular level (proteins, small molecules, atoms) Scanning em: directly produces an image of the 3d structure of the surface of a specimen.
