BRAINCAKETransmission Electron Microscope
In a transmission electron microscope (TEM), a beam of electrons is passed through a very thin specimen. Areas that absorb or scatter many electrons appear dark on the image; areas that let electrons through appear light.
Preparing the specimen
• The tissue is fixed with chemicals to preserve its structure, then dehydrated.
• It is embedded in resin and cut into extremely thin sections (often less than 100 nm thick) using an ultramicrotome.
• It is stained with salts of heavy metals such as lead or uranium (or osmium). These scatter electrons, so membranes and other structures that take up the stain appear dark and give contrast.
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Key terms in this lesson
- artefact
- A structure seen in a microscope image that was created by the preparation process and was not present in the living specimen.
- resolution
- The smallest distance between two points that can still be seen as two separate points; higher resolution shows more detail.
More in Eukaryotic Cells
- Magnification and Resolution
- Light Microscope
- Electron Microscope
- Scanning Electron Microscope
- Ultrastructure
- Membranes
- Phospholipid Bilayer
- Membrane Proteins
All 30 lessons in Eukaryotic Cells · All Edexcel AS-level Biology topics