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Structure of plant and animal cells under an electron
microscope
Advanced Higher BiologyCell and molecular Biology
The Electron Microscope• Two main advantages
– High resolving power (short wavelength of electrons)
– As electrons negatively are charged the beam can be focused using electromagnets
• As electrons are absorbed by molecules of air, a near-vacuum has to be created within the chamber of an electron microscope.
The Electron Microscope• Two types
– Transmission Electron Microscope (TEM)
– Scanning Electron Microscope (SEM)
• Activity– Read through the handout on the
electron microscope– Answer discussion questions 1 - 4
Comparison of advantages and disadvantages of the light and electron microscopes
Light MicroscopeAdvantages
Electron Microscope Disadvantages
Small and portable very largeOperated in special rooms
Unaffected by magnetic fields Affected by magnetic fields
Preparation of material is quick and simple
Preparation of material is lengthyRequires expertise
Material rarely distorted by preparation
Preparation may distort material
Natural colour of object observed Images are in black and white
Cheap to purchase and operate Expensive to purchase and operate
Comparison of advantages and disadvantages of the light and electron microscopes
Light MicroscopeDisadvantages
Electron MicroscopeAdvantages
Magnifies objects up to 1500x only
Magnifies objects more than 500 000X
Depth of field is restricted
Possible to investigate a greater field of depth
Pupil Activity• Cell structure
– Read through the information on each of the organelles as you colour them in
– Follow the guidance on colouring them in given at the bottom of the page
– This works on the theory that whilst you are colouring in, you have time to consider and think about the structure and function of the organelles