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

Comparison of pathways of the light and electron microscopes

Ultrastructure of an animal cell as seen through an electron microscope

Ultrastructure of a plant cell as seen through an electron microscope

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