Cell theory and microscopy Flashcards
What are cells? Light microscopy Electron microscopy Recent advances
What is the average size of a cell?
2-200 um
How are cells formed?
Cells arise only by division of a pre-existing cell
What is resolution?
The ability to discriminate parts of an image
What are the properties of light microscopy?
A condenser lens focuses a beam of light onto the specimen. Limit resolution of 0.2 um (1000x). Poor contrast and usually involves cell death due to staining
What is the total magnification equation?
Total magnification = objective lens x eye piece lens
What is phase contrast microscopy?
Uses refraction to highlight intracellular components
What is differential interface contrast microscopy?
Rates of change in refractive index to produce a 3D image
What is fluorescence microscopy?
Specimen stained with fluorescent dye to produce high contrast image
What are the 4 steps to prepare a sample for light microscopy?
Fixation - stops sample falling apart
Embed - mechanical support (resin)
Section - cut a thin section to analyse
Staining - improves visibility of thin sections
What is laser scanning microscopy?
A focused laser beam excites fluorescent molecules in cells and tissues. Forms a 3D image on a PC. 300um max
What is transmission electron microscopy?
Electrons pass through a thin specimen. Allows up to 1,000,000x magnification. Specimens must be fixed, dehydrated and stained. You can also use freeze-fracture
What is scanning electron microscopy?
Electron beam scanned over a specimen and the electrons bounce back and are detected. Provides a 3D image and 15-150,000x magnification
What is cryo-electron microscopy?
Use deep frozen molecules in a solution and gentler beams to determine structure
