Electron Microscopy

Question 1

Resolution

Answer 1

Shows structures within organelles, lipid membranes, viruses, macromolecules
E.g. DNA, proteins

Question 2

Transmission electron microscopy

Answer 2

Electron beam penetrate specimen
Vacuum
Specimen fixed
Electromagnetic lenses
Resolution 0.5-10nm
Electrons interact w/ phosphorescent screen
Increase contrast using electron dense stains (heavy metal salts: lead, uranium) - scatter electrons
Thin plastic resin sections (50-100nm thick)
Resin better support thinner sections
Serial sections - 3D (takes ages!)

Question 3

Scanning electron microscopy

Answer 3

Electrons form probe 
Scanned across sample surface 
Thick sample
Emitted signal go to detectors 
Resolution 0.2-2nm 
Resolution depend on diameter probe and volume of interaction w/ sampe 
Specimen fixed as LM/TEM 
Conducting coating - min build up electrons (reduce detail)