Transcript Structure of plant and animal cells under an electron

Structure of plant and animal
cells under an electron
microscope
Advanced Higher Biology
Cell 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 Microscope
Advantages
Electron Microscope
Disadvantages
Small and portable
very large
Operated in special rooms
Unaffected by magnetic fields
Affected by magnetic fields
Preparation of material is quick
and simple
Preparation of material is lengthy
Requires 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 Microscope
Disadvantages
Electron Microscope
Advantages
Magnifies objects up Magnifies objects
to 1500x only
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