microscopy Flashcards
why does electron microscopy provide better resolution than light microscopy?
the wavelength of electrons is much shorter than visible light.
therefore electrons emitted by a sample can be very close without interfering with eachother.
explain transmission electron microscopy (TEM)
a beam of electrons is fired at a sample
the image is produced by electrons that are TRANSMITTED through the sample
explain scanning electron microscopy
a beam of electrons are fired at a sample
the image is produced by electrons that are EMITTED through the sample
in which type of microscopy are you able to see the 3D structure of a cell?
scanning electron microscopy (SEM)
list 2 differences between light microscopy and electron microscopy
electron microscopy provides higher magnification and resolution
electron microscopy must be enclosed in a vacuum
State 3 ways TEM is different to SEM
high energy electrons are used
sample is thin
internal structures are visible (2D)
how could a student prepare a mount of tissue for a LIGHT MICROSCOPE? (4)
- Obtain a THIN section of tissue
- Place plant tissue in a drop of water
- Stain tissue on a slide
- Add coverslip with a mounted needle, at 45 degrees to prevent air bubbles
what is an artefact?
visible details that aren’t part of the observed specimen e.g. air bubbles
which electron microscope provides higher resolution?
transmission electron microscope
what is differential staining?
using multiple stains to distinguish between different cells and organelles
what is the purpose of a stain?
increases contrast, allowing cell components to become visible
what does Acetic orcein stain in the cell?
It binds to DNA and stains chromosomes dark red
what does Eosin stain in the cell?
it stains cytoplasm and extracellular proteins pink
what does Methylene blue stain in a cell?
stains acidic structures
what is gram staining?
a type of differential staining, distinguishing between gram positive and gram negative bacteria based on the cell wall structure
