2.2 Electron microscopy

Question 1

electron microscope

Answer 1

• electron microscope resolves the fine structure of cell
• biological specimens require special preparation for the EM
• multiple images combined to increase resolution
• different views of single object combined - 3D reconstruction
• specific macromolecules localized by immunogold EM
• images of surfaces obtained by scanning EM

Question 2

Transmission electron miscroscope

Answer 2

• tungsten filament
• negative shield
• anode accelerates beam
• magnetic lenses - coil of wire generates strong magnetic field
• electrons charged particles - deflected
• vacuum
• thin + dry specimen
• static charge -> deflect electrons
• copper plate - electrical earth
• monochrome

Question 3

Scanning electron microscope

Answer 3

• video technology
• used for dense structures
• 3D - better solution
• detector not focus
• electrical signal generated
• back-scattered electrons (high energy) - surface shape + nature of specimen
• secondary electrons (low energy) - escape at top 2 nm surface - shape
• auger electronsproduced by x-rays - interaction with specimen
• x-rays emitted - used to identify elements