module 2 - 2.3 more microscopy Flashcards
what are the main components of a light microscope?
they have 2 lenses which reduced chromatic abberation
typical magnification 1500x (theoretical resolution)
why do light microscopes have 2 lenses?
to reduce chromatic abberation
what are the disadvantages of light microscopy?
- increased magnification
- increased resolution NOT easily achieved (due to limit of resolution of 200nm/0.2μm
what are the advantages of electron microscopy?
- electrons can be waves or particles, wave particle duality
- resolution from 0.5nm to 10nm
- electron microscopes allow cells ultrastructure to be seen
what are the 2 types of electron microscopes?
transmission electron microscope (TEM)
scanning electron microscope (SEM)
what are the components of a transmission electron microscope?
- sample embedded in resin, stained with heavy metal compounds & cut into thin sections in ultramicrotome
- specimen is ultra-thin section, between 70-350nm
- beams of electrons in vacuum are transmitted through sample
- image magnified and focused onto an imaging device
what are 3 examples of imaging devices?
fluorescent screen, layer of photographic film, or sensor
what are the components of a scanning electron microscope?
- produces image of sample by scanning surface with beam of electrons in a vacuum
- electrons interact with atoms
- covered with electrically conducting material
what is an artefact?
visual anomalies during visual representation
what is a mesosome?
they are invaginations in the plasma membrane of bacteria
produced by chemical fixation techniques
what are some differences between light and electron microscopes?
LIGHT- inexpensive to buy and operate, small and portable, simple sample prep, no vacuum required, natural colour/ stain, living specimen
ELECTRON - expensive to buy and operate, large and installed, complex sample prep, vacuum required, black and white image, dead specimen
what are some components of laser scanning confocal microscopes?
- optical microscope
- single focused light from a laser is moved across the specimen, causes fluorophores in the specimen to fluorescence
- higher optical resolution and contrast