Chapter 2: 2.3 Flashcards
More microscopy
Electron microscopy - what is used to illuminate the specimen?
A beam of electrons with a wavelength of less than 1 nm.
Why can be more detail be present in an electron Microscope than a light microscope?
Electrons have a much smaller wavelength than light waves
What are the disadvantages of electron microscopy?
- Expensive equipment
- Can only be used in a controlled environment
- Specimens can be damaged by the electron beam
What are the two types of electron microscope?
- Transmission electron microscope (TEM)
- Scanning electron microscope (SEM)
What does a transmission electron microscope do?
Fires a beam of electrons through a specimen - the beam is then focused to produce a high-resolution image
What does a scanning electron microscope do?
Fires a beam of electrons is sent across the surface of a specimen and reflected electrons are collected.
beam focused to produce a less high-resolution image than a TEM.
Provides 3D images of specimen surfaces.
What light and electron microscope similarities and differences?
LIGHT ELECTRON
- inexpensive - expensive
- small/portable - large (requires installation)
- simple sample prep - complex sample prep
- no distortion created - distortion created
- vacuum not required - vacuum required
- natural sample colour - black and white images
is seen/stains used produced
- resolving power =
200nm - x500,000 magnification
- specimens can be - specimens can be dead
living OR dead
Can scientific drawings be produced from light microscopes or electron microscopes?
Electron microscopes - they provide much better resolution.
What does a laser scanning confocal (LSC) microscope work to view a sample?
It moves a single spot of focused light across a specimen, which causes fluorescence from the components labelled with a fluorescent chemical, or ‘dye’.
The emitted light is filtered through a pinhole aperture
Only light radiated very close to the focal plane (the distance that gives the sharpest focus) is detected.
What can be done to produce an image at high resolution with a laser scanning confocal (LSC) microscope?
By examining very thin sections of the specimen
Light from elsewhere can be removed
Where is laser scanning confocal (LSC) microscopy currently used?
- Diagnoses of diseases of the eye
- Being developed for use endoscopic procedures
- Development of new drugs
Name one future use for advanced optical microscopy?
In virtual biopsies
Where is GFP (Green fluorescent protein) produced?
The jellyfish [Aequorea victoria].
How has GFP (Green fluorescent protein) been adapted for use?
GFP molecules have been engineered to fluoresce different colours. This means that different components of a specimen can by studied at the same time.
What is the maximum magnification that can be achieved by an Electron Microscope? What is the resolution like?
they can provide images with a magnifications of up to x500,000
The resolution is clear
