The Study Of Subcellular Organisation Flashcards
What is transmission electron microscopy?
Electrons are passed through a sample and then focused onto a fluorescent screen.
Samples are stained with heavy metals, such as lead & uranium. These large atoms prevent electrons passing straight through the section.
Uranium binds preferentially to nucleic acids and proteins.
Lead binds preferentially to lipids.
What is the limiting factor that prevents small structures being discriminated using a light microscope?
The wavelength of visible light.
Describe the typical appearance of a transmission electron microscopy & explain why it appears this way.
Cell components rich in lipids, proteins & DNA prevent the passage of electrons through staining with heavy metals.
These areas appear dark or ‘electron dense’ on the viewing screen.
Less concentrated areas, such as the cytosol, appear light or ‘electron-Lucent’.
What is immunoelectron microscopy?
Immunolabelling where the antibody is tagged with electron-dense substances, such as small gold particles which can be observed as dark dots under transmission electron microscopy.
What is cell fractionation?
The separation of cell components for individual study, carried out in two steps:
1) disruption of the cells to release the sub cellular components.
2) centrifugation to separate the components on the basis of their mass or density.
Explain centrifugation.
Centrifugal force is generated by rapid spinning. Particles of different sizes will migrate through suspension at different rates.
