BRAINCAKEElectron Microscope
An electron microscope uses a beam of electrons instead of light. Electrons have a much shorter wavelength than light, so the resolution is far higher: an electron microscope can resolve objects well under 1 nm apart, compared with about 200 nm for a light microscope. Magnifications of more than ×500 000 are possible, which shows the ultrastructure of cells, such as membranes, ribosomes and the inner structure of mitochondria.
Electrons cannot be focused by glass, so electromagnets act as the lenses. The image is formed on a fluorescent screen or detector and recorded as an electron micrograph. Micrographs are black and white; any colour is added afterwards by computer (false colour).
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Key terms in this lesson
- ultrastructure
- The fine details of cell structure, including the internal structure of organelles, that can be seen only with an electron microscope.
- artefact
- A structure seen in a microscope image that was created by the preparation process and was not present in the living specimen.
More in Eukaryotic Cells
- Magnification and Resolution
- Light Microscope
- Transmission Electron Microscope
- Scanning Electron Microscope
- Ultrastructure
- Membranes
- Phospholipid Bilayer
- Membrane Proteins
All 30 lessons in Eukaryotic Cells · All Edexcel AS-level Biology topics