THE LIGHT MICROSCOPE AND THE ELECTRON MICROSCOPE © 2007 Paul Billiet ODWS
Dec 17, 2015
UNITS OF MEASUREMENT
1m = 103 mm (millimetres)1m = 106 µm (micrometres)1m = 109 nm (nanometres)
Sometimes in old texts Angstroms (Å) are used (the diameter of a hydrogen atom)
1m = 1010 Å
© 2007 Paul Billiet ODWS
THE LIGHT MICROSCOPE v THE ELECTRON MICROSCOPE
fluorescent (TV) screen,photographic film
Human eye (retina), photographic film
Focussing screen
VacuumAir-filledInterior
MagnetsGlassLenses
High voltage (50kV) tungsten lamp
Tungsten or quartz halogen lamp
Radiation source
x500 000x1000 – x1500Maximum magnification
0.2nmFine detail
app. 200nmMaximum resolving power
Electronsapp. 4nm
Monochrome
Visible light760nm (red) – 390nm
Colours visible
Electromagnetic spectrum used
ELECTRON MICROSCOPELIGHT MICROSCOPEFEATURE
© 2007 Paul Billiet ODWS
THE LIGHT MICROSCOPE v THE ELECTRON MICROSCOPE
Copper gridGlass slideSupport
Heavy metalsWater soluble dyesStains
Microtome only.Slices 50nm
Parts of cells visible
Hand or microtomeslices 20 000nmWhole cells visible
Sectioning
ResinWaxEmbedding
OsO4 or KMnO4AlcoholFixation
Tissues must be dehydrated
= dead
Temporary mounts living or dead
Preparation of specimens
ELECTRON MICROSCOPE
LIGHT MICROSCOPEFEATURE
© 2007 Paul Billiet ODWS
CELL STRUCTURE AND MICROSCOPYSUBCELLULAR STRUCTURE EUKARYOTES PROKARYOTES
ANIMAL CELLS PLANT CELLS
Cell wall - + +
Plasma membrane + + +
Nucleus & nucleoli + + -
Chromosomes + + Circular loop of DNA
Centrioles + + -
Mitochondria + + -
Plastids (chloroplasts, chromoplasts etc.) - + -
Sap vacuole - + -
Food vacuoles Some + -
Contractile vacuoles Some + -
Pseudopods Some + -
Cilia Some + -
Flagellae Some Some Rotating
Microtubules + + -
Lysosomes + + -
Golgi apparatus + + -
Microvilli Some + -
© 2007 Paul Billiet ODWS
CELL STRUCTURE AND MICROSCOPY
SUBCELLULAR STRUCTURE EUKARYOTES PROKARYOTES
ANIMAL CELLS PLANT CELLS
Endoplasmic reticulum + + -
Nuclear envelope & pores + + -
Vesicles + + -
Ribosomes +(bigger) +(bigger) +(smaller)
Mesosome + + +
Organelle membranes + + -
Macromolecular structures + + +
© 2007 Paul Billiet ODWS