Cell Theory and Microscopy Flashcards
What is the typical size of cells?
2-200 micrometres in diameter
What is Cell theory?
1) All organisms are composed of one or more cells
2) Cells are the smallest units of life, forming the basis of organization in all living things
3) Cells arise only by division of a pre-existing cell
What are the limits of resolution and magnification in Light Microscopy?
Resolution - 0.2micrometres
Magnification - 1000x approximately
How is total magnification calculated?
Total Magnification = Magnification of objective lens X magnification of eyepiece lens
What is fluorescence microscopy?
Specimen is stained with fluorescent dye or protein. UV light is then used to excite specimen to produce a high contrast image on a dark background
How does the specimen need to be prepared to carry out light microscopy?
1) Fixation - Immobilises cell material
2) Embed - Providing mechanical support
3) Section - Cut thin section no more than 10 micrometres thick
4) Staining - improves visability of thin sections
What is transmission electron microscopy (TEM)?
Electrons pass through a very thin specimen (less than 0.1micrometres) and is used to see the insides of cells
What is the resolving power and magnification of TEM?
Resolving power - 2-20nanometres
Magnification - up to 1,000,000x
What is scanning election microscopy (SEM) ?
An electron beam is scanned over the surface of a specimen and the electrons bounce off and hit detectors. Provides information about the surface details of the cell which provides a three dimensional image.
What is the magnification of SEM?
Magnification= 15-150,000x
What are the recent advance in microscopy?
1) Cryo-Election Microscopy which uses deep frozen molecules and gentler electron beams to determine structure of biomolecules
2) Atomic Force Microscopy. Methos to visualise surfaces at molecular scale using a reflected laser beam
