THE LIGHT MICROSCOPE AND THE ELECTRON MICROSCOPE Transmission electron microscope Compound light microscope © 2016 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 © 2016 Paul Billiet ODWS
The electromagnetic spectrum © 2016 Paul Billiet ODWS
Light v Electron © 2016 Paul Billiet ODWS
Magnifying using the Light Microscope © 2016 Paul Billiet ODWS
Magnifying using the Electron Microscope © 2016 Paul Billiet ODWS
THE LIGHT MICROSCOPE v THE ELECTRON MICROSCOPE FEATURE Electrons app. 4nm Monochrome Visible light 760nm (red) – 390nm Colours visible Electromagnetic spectrum used 0.2nm Fine detail app. 200nm Maximum resolving power x500 000 x1000 – x1500 Maximum magnification High voltage (50kV) tungsten lamp Tungsten or quartz halogen lamp Radiation source Magnets Glass Lenses Vacuum Air-filled Interior fluorescent (TV) screen, photographic film Human eye (retina), photographic film Focussing screen © 2016 Paul Billiet ODWS
THE LIGHT MICROSCOPE v THE ELECTRON MICROSCOPE FEATURE Tissues must be dehydrated = dead Temporary mounts living or dead Preparation of specimens OsO4 or KMnO4 Alcohol Fixation Resin Wax Embedding Microtome only. Slices 50nm Parts of cells visible Hand or microtome slices 20 000nm Whole cells visible Sectioning Heavy metals Water soluble dyes Stains Copper grid Glass slide Support © 2016 Paul Billiet ODWS
Embedding in resin © P Billiet © 2016 Paul Billiet ODWS
Microtome knife © 2016 Paul Billiet ODWS © P Billiet
Copper grid slides © 2016 Paul Billiet ODWS © P Billiet
CELL STRUCTURE AND MICROSCOPY SUBCELLULAR STRUCTURE EUKARYOTES PROKARYOTES ANIMAL CELLS PLANT CELLS Cell wall - but may have an extracellular matrix + + but not of cellulose Plasma membrane + cholesterol present Nucleus & nucleoli - Chromosomes + (DNA + Protein) Circular loop of DNA Centrioles Mitochondria Plastids (chloroplasts, chromoplasts etc.) Sap vacuole Food vacuoles Some Contractile vacuoles Pseudopods Cilia Flagellae Rotating Microtubules Lysosomes Golgi apparatus Microvilli
CELL STRUCTURE AND MICROSCOPY SUBCELLULAR STRUCTURE EUKARYOTES PROKARYOTES ANIMAL CELLS PLANT CELLS Endoplasmic reticulum + - Nuclear envelope & pores Vesicles Ribosomes +(80S) +(70S) Organelle membranes Macromolecular structures © 2016 Paul Billiet ODWS