studying cells (microscopy) Flashcards
why do we use microscopes?
to observe and investigate cell structure.
what are the 2 types of microscope?
light microscope and electron microscope
why do we use different types of microscope?
to study cells at different levels of detail
what is the maximum resolution of a light microscope
0.2 micrometres
what is the maximum useful magnification of a light microscope
x1500
what can a light microscope be used to observe
entire cells
nuclei
mitochondria
chloroplasts
what are the advantages of using a light microscope?
-they are small and relatively cheap
-specimen prep is straightforward
-they produce colour images
-allow the observation of living specimen
what is an electron microscopes maximum resolution
0.0002 micrometres
what is the maximum useful magnification of an electron microscope
from x1,000,000 up to many millions.
what can an electron microscope be used to observe
small structures inside cells:
- cell membranes
-ribosomes
-endoplasmic reticulum
-lysosomes
what are the disadvantages of an electron microscope
-very large and expensive
-complex specimen preparation
-specimens must be viewed in a vacuum
- dead specimens only
-black and white images
what are the 2 types of electron microscope
transmission electron microscope and scanning electron microscope
how does a transmission electron microscope work
TEMS use electromagnets to transmit a beam of electrons through a specimen.
the denser parts of the specimen absorb more electrons making them appear darker on the final image.
what are the qualities of TEM images
high resolution
ultrastructure of cells can be seen
2-D
how does a scanning electron microscope work?
they pass a beam of electrons across the surface of a specimen and then detect the rate at which the electrons bounce back.
what are the qualities of an SEM image
3-D
show the surface of specimens
* they have a much lower resolution than TEMS
how does a light microscope work?
Light is directed through the thin layer of biological material that is supported on a glass slide
This light is focused through several lenses so that an image is visible through the eyepiece
The magnifying power of the microscope can be increased by rotating the higher power objective lens into place
