Notesale: Turn your study into money

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CHAPTER 2 : Basic components of living systems
More microscopy
Electron microscopy
-Beam of electrons with wavelength of less than 1mm used to illuminate specimen
-More detail of cell ultrastructure can be seen because electrons have a smaller
wavelength than light waves
-Clear resolution of images of up to x500 000 magnification
-Very expensive
-Only used in controlled environment, dedicated space
-Specimens can be damaged by electron beam because of complex preparation
process, problem with artefacts
Two types of electron microscope:
Transmission electron microscope (TEM) - beam of electrons transmitted
through specimens and focused to produce an image
...
5nm
Scanning electron microscope (SEM) - beam of electrons sent across the
surface of specimen and reflected electrons are collected
...

A comparison of light and electron microscopy
Light microscope

Electron microscope

Inexpensive to buy and operate

Expensive to buy and operate

Small and portable

Large and needs to be installed

Simple sample preparation

Complex sample preparation

Sample preparation doesn't usually lead
to distortion

Sample preparation often distorts
material

Vacuum isn't required

Vacuum is required

Natural colour of sample is seen (or
stains are used)

Black and white images produced (can
be coloured digitally)

Up to x2000 magnification

Over x500 000 magnification

Resolving power is 200nm

Resolving power of TEM os 0

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