Module 1 - Cells

Section about cell size, magnification and electron microscopes.

HideShow resource information
  • Created by: Nick
  • Created on: 02-05-10 17:23

Cell size, magnification, electron microscopes

Cells can be prepared by;

Staining - Coloured stains are chemicals that bind to chemicals on or in the specimen. They allow the specimen to be seen. Some stains bind to specific cell structures.

Sectioning - Specimens embedded in wax. Thin sections are then cut without distorting structure. Particularly useful for making sections of soft tissue e.g. brain.

Actual size = Image size/Magnification. um - micrometre, nm - nanometre


Diameter = 5 um

Measure diameter - 25mm

Multiply by 1000 (um) - 25000um

Divide diameter by actual size 25000/5000 -Magnification = 5000x-

1 of 2

Cell size, magnification, electron microscopes

Transmission electron microscope (TEM)

  • Electron beam passes through a very thin prepared sample.Produces 2D image.
  • Electrons pass through the denser parts of sample less easily, giving contrast.
  • Magnification possible is x500,000.

Scanning electron microscope (SEM)

  • Electron beam directed onto a sample, not through. They 'bounce off' the sample.
  • Final 3D view of surface of sample produced.
  • Magnification possible is x100,000.

Advantages & Limitations of electron microscope.

  • Adv - Resolution is 2000x more than in the light microscope.
  • Adv - Therefore can be used to produce detailed images of structure inside cells.
  • Dis adv - Have to be in a vacuum as electron beams deflected by molecules in air.
  • Dis adv - Preparation & use of electron microscope require high skill and training.
2 of 2


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes and structure resources »