studying cells Flashcards
how do optical microscopes work?
- beam of light passes through, starting at the bottom of the microscope
- beam travels upward through sample on the stage
- passes through objective and eyepiece lens , magnifying the image
– to find the magnification, multiply the power of the two lenses
- the beam of light passes into the eye so we can see the image
SAMPLE MUST BE THIN SO LIGHT CAN PASS THROUGH
how does an electron microscope work?
- beam of electrons produced by electron gun at the top of the microscope
- beam travels down the microscope in a VACUUM
- beam travels through sample
– ELECTROMAGNETICS are used instead of glass lenses
– BLACK AND WHITE image produced at the bottom
why is a vacuum used in a TEM?
so no air molecules get in the way of the electrons
what is an artefact?
things that result from the way the specimen is prepared
how does an SEM produce a 3D image?
electrons are scattered from the surface of the sample
advantages and disadvantages of an optical microscope
colour image
vacuum isn’t needed
long wavelength = low resolution
thin samples needed
2D image
advantages and disadvantages of a TEM microscope
shorter wavelength = higher resolution
black and white image
thin sample needed
vacuum needed
what is cell fractionation?
process where different parts and organelles of a cell are separated
what property results in the order the organelles form the pellets?
the density of organelles
what organelle forms the first pellet?
nuclei
what organelle forms the pellet at a medium speed?
mitochindria
chloroplast
what organelle forms the pellet at the highest speed?
ribosomes
what are the properties of the liquid the cells are in?
ice cold
isotonic
buffer
why does the solution have to be ice cold?
to stop/reduce enzyme activity within the organelles
why does the solution have to be isotonic?
to prevent organelles bursting by water movement via osmosis
why does the solution have to be a buffer?
to maintain the pH of the oganelles
