Methods of Studying Cells Flashcards
What is ultracentrifugation?
- centrifugation is a method used to separate structures of different density
Advantage of electron microscope
-uses electrons which have a shorter wavelength and therefore greater resolution than light microscopes
-unlike electron microscopes, light microscopes get blurred at higher magnification
Optimal conditions for UC (3)
- Isotonic solution as it prevents osmotic movement in or out of organelles
- Ice cold temperature to minimalize/ stop enzyme activity (preventing autolysis of the organelles)
- buffer solution to maintain the pH so the proteins aren’t denatured
Describe the process of Ultracentrifugation
- cells are broken open by homogenising a tissue in optimal conditions using a blender
- resulting suspension may be filtered to remove cell debris eg. cell walls or unburst cells
- the homogenate is centrifuged at a low speed which makes the densest organelles form a pellet at the bottom
- the supernatant (the liquid remaining) is centrifuged again at a higher speed for longer where the 2nd densest organelles forms a pellet
- repeat process by increasing speed and duration of centrifugation of in order to get several other pellets
In a light microscope the specimen must be?
-thin so that light passes through it and it is visible
-be stained in order to make structures visible
Order of pellet formation
-nuclei
-chloroplast( if plant cell)
-mitochondria
-endoplasmic reticulum
-ribosomes
How does an electron microscope work?
It uses a beam of electrons which are focused using electromagnets.
I AM equation?
Image size = Actual Size x Magnification
Differences between Scanning Electron Microscope and Transmission Electron Microscope
- TEM has a higher resolution than SEM
- TEM produces images of internal structures, SEM produces images of external structures
- TEM gives 2d image, SEM gives 3d image
Similarities between Scanning Electron Microscope and Transmission Electron Microscope
- Both use electron beams focused by electromagnets
