cell structure Flashcards
what is the resolution and mag of an optical microscope?
res - 200nm
mag - up to 1500x
what is the resolution and mag of a scanning electron microscope?
res - 1 nm
mag - up to 100 000x
what is the res and mag of a transmission electron microscope?
res- 0.2 nm
mag - 2 000 000 x
how does a confocal microscope work?
use intense beams of light to scan the specimen, which is tagged with a flurecent dye. the laser causes the dye to give off light which is focused through a pinhole (blocks any unfocused light) onto a detector which is hooked up to a computer to give an image. can be used to look at different depths in different specimens.
how does a transmission electron microscope work?
It uses electromagnets to focus a beam of electrons through a specimen. Denser parts of the specimen will absorb more electrons which makes them appear darker. used to study a range of organells.
how does a scanning electron microscope work?
it scans a beam of electrons across the specimen, this knocks off electrons form the specimen which are collected by a cathode tube to form a 3D but lower res compared to the TEM
why do we stain our samples?
because in light microscopes light will pass through the specimen, an image will form because some parts will absorb more light. Sometimes the whole specimen will look transparent because the light will just pass straight through which makes studying it really hard. so we stain them.
what is differential staining ?
When some stains will stain different structures of the cell so they can be easily identified.
how does staining work?
stains are coloured chemicals that will bind to molecules in or on the specimen.
what does acetic orcein stain?
binds to DNA and stains chromazones dark red
what does eosin stain?
cytoplasm
what does Sudan red stain ?
lipids
what does iodine stain?
cellulose in plant cell walls yellow
and stains starch blue/black, under a microscope this will look violet
how do you make perminently fixed slides?
dehydrate the specimen- so that no bactiria can survive to decompose it
embedd them in wax- to pervent shape distortion
slice thinly - so that light/ electrons can get through.
how do you prepare a dry mount slide?
Thinly slice the specimen
Use tweezers to pick it up and put in the middle of slide
Put a cover slipe over the top
how to prepare a wet mount?
use a pipette to put a drop of water on slide, then place specimen ontop
to put the cover slip on stand the slip upright next to water drop, tilt slip and lower it onto the specimen
try not to get air bubbles under there
next add a stain, put a drop on one side of the cover slip and put a peice of paper towel on the opposite side to draw the stain from one side to the other under the cover slip.