2.1 cell structure Flashcards
light microscope
living samples
colour image
poor resolution due to long wavelength of light
transmission electron microscope
high magnification and resolution
stained and put in vacuum
electrons pass through specimen
parts of specimen absorb electrons so they appear darker
2D detailed image
scanning electron microscope
high magnification and resolution
electrons beamed onto surface and are scattered in different ways depending on contours
3D image
laser scanning confocal microscope
(fluorescent microscope)
high resolution
high light intensity
stained with fluorescent dye
3D imaging
laser light used to create image
as light is emitted from specimen it causes fluorescence
resolution
the minimum distance between two objects in which they can still be viewed as separate
magnification
how many times larger the image is compared to the object
optical microscope
determined by wavelength of light
electron microscope
determined by wavelength of the beam of electrons
electromagnet used to focus beam of e-
black and white image
why must an electron microscope be used in a vacuum?
electrons are absorbed by air
dry mount
thin slices or whole specimens viewed with just the coverslip placed on top
wet mount
water is added to specimen before lowering the coverslip with a mounted needle to prevent air bubbless
squash slide
wet mounts which you push down on the coverslip to squash the sample to ensure a thin layer for light to pass through
smear slide
using the edge of another slide to smear the sample across another slide to create a smooth, thin, even coated specimen then a coverslip placed on top of smear
eyepiece graticule
(light microscopes) scale on glass disc which is used to measure the size of objects you are viewing
how to calibrate eyepiece graticule
- line up stage micrometre and eyepiece graticule whilst looking through eyepiece
- count how many divisions on eyepiece graticule fit into one division on micrometre scale
- each division on micrometre is 10 micrometres, this can be used to calculate what one division on the eyepiece graticule is at that current magnification
formula for magnification
magnification = size of image/actual size
mm to micrometres
x 1000
differential staining
many chemical stains being used to stain different parts of a cell in different colours