ELECTRON MICROSCOPY
LIMITATIONS OF THE LIGHTMICROSCOPE
•Light microscopes rely on visible light being refracted tomagnify the image.
•Scientists were unable to study organelles without theinvention of a new, higher powered microscope.
Was invented inthe 1950s.
THE ELECTRONMICROSCOPE
THE ELECTRON MICROSCOPE
•Rather than light, an electron microscope focuses abeam of electrons onto or through the specimen.
•Modern electron microscopes are capable of obtainingresolutions up to 100 times that of standard lightmicroscopes.
THE ELECTRON MICROSCOPE
•Electron microscopes come in 2 varieties:
•Scanning electron microscopes (SEM)
•Transmission electron microscopes (TEM)
Both are used in Biology for today, but fordifferent purposes.
SCANNING ELECTRON MICROSCOPES
•Are used to to studythe topography, oroutside surface of thespecimen. In anSEM, the electronbeam scans thesurface of thespecimen
SEM image of amidge (a small fly)
SCANNINGELECTRONMICROSCOPE
TRANSMISSION ELECTRONMICROSCOPES (TEM)
•Are used to study theinternal structure ofcells
•TEM aim an electronbeam through a verythin section of thespecimen, similar tothe way a lightmicroscope transmitslight through a slide.
TRANSMISSION ELECTRONMICROSCOPES (TEM)
ROUGH ENDOPLASMIC RETICULUM
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Spot thedifference?
The ‘spots’ are thedifference!
The RoughEndoplasmic Reticulumis peppered withribosomes that give itthe rough appearance
It is where proteinsynthesis occurs
GOLGI APPARATUS
PLANT CELL VACUOLE
MITOCHONDRIA
CHLOROPLASTS
