THE LIGHT MICROSCOPE AND THE ELECTRON MICROSCOPE

© 2007 Paul Billiet ODWS

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 electromagnetic spectrum

© 2007 Paul Billiet ODWS

Light v Electron

© 2007 Paul Billiet ODWS

Magnifying using the Light Microscope

© 2007 Paul Billiet ODWS

Magnifying using the Electron Microscope

© 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

Embedding in resin

© 2007 Paul Billiet ODWS

Microtome knife

© 2007 Paul Billiet ODWS

Copper grid slides

© 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