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Unformatted text preview: BIO115 The Cell Jessica Pamment Overview • Discovery of the cell • How cells are studied • Eukaryotes vs. Prokaryotes • Cell anatomy History Timeline • 1665 Robert Hooke coined the word ‘cell’ • 1674 Antoine Van Leeuwenhoek was first to observe live cells • 1839 Schleiden and Schwann proposed the cell theory Robert Hooke’s cork cells QuickTimeª and a decompressor are needed to see this picture. The Size Range of Cells Microscopy Terms • Resolution­ measures the clarity of an image • Magnification­ ratio of an image’s size to its real size Different views of a protist, Euglena Euglena Cells in motion Cells in motion • http://video.search.yahoo.com/search/vide o;_ylt=A0SO8ZlTGy1N4j4AG277w8QF;_yl u=X3oDMTBncGdyMzQ0BHNlYwNzZWFy Y2gEdnRpZAM­?p=amoeba&fr=yfp­t­701­ s&ei=utf­8&fr2=tab­ web&n=21&tnr=18&y=Search TECHNIQUE RESULTS e) Fluorescence 50 µm Light Microscopy • First built in the 1600s • Resolution is 0.2 µ m • Magnification is X 1­2000 • Lens refracts light passed through a specimen to result in a magnified image • Bacteria and mitochondria smallest objects discernible by light microscope Electron Microscopy • Introduced in 1950s • Uses beams of electrons instead of light • Resolution of TEM is 3­10 Angstroms • Magnification up to 2 X 106 • Can’t be used to view live cells Electron Microscopy • Disadvantages: i. Can’t be used to view live cells ii. Artifacts often introduced due to specimen preparation method • Advantage is superior resolution • SEM used for study of surfaces • TEM used for study of internal structure TECHNIQUE RESULTS (a) Scanning electron microscopy (SEM) Cilia 1 µm (b) Transmission electron Longitudinal Cross section section of of cilium microscopy (TEM) 1 µm cilium Differences between bacteria and eukaryotes Character Bacteria/archae Eukarya a Nuclear Envelope Absent Present Membrane­ enclosed organelles Circular chromosome Absent Present Present Absent Similarities between bacteria and eukaryotes • Bound by a plasma membrane • Contain cytosol in the area enclosed by plasma membrane • Contain chromosomes • Contain ribosomes A Prokaryotic Cell Prokaryotic Micrograph of Bacterium Micrograph Cell Membranes Cell Membranes • 8 nm thick • Fluid mosaic model of lipids and proteins • Dynamic, fluid structures • Lipid b...
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