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Transcript
CHAPTER 7: A TOUR OF THE CELL RESOLUTION Human Eye 0.1mm, 100µm, 100,000.0nm. Light Microscope 0.0002mm 0.2µm, 200.0nm 2000.0Å S.E.M. 0.002µm 2.0nm 20.0Å T.E.M. 0.0001µm 0.1nm. 1.0Å wavelength of light wavelength of electrons 0.4--0.7µm. 400—750nm. 0.0054nm--0.0000054nm Theoretically 130,000 times better resolution Now only 2,000 times better resolution Transmission Electron Microscope TEM TEM Scanning Electron Microscope SEM TEM SEM Light Microscope SPECIMEN PREPARATION 1. Staining a. light--use pigmented molecules which are absorbed differentially by the specimen b. T.E.M.-- use heavy metals; which are also absorbed differentially c. S.E.M.--not necessary 2. Fixation--use a chemical which will tie the tissue together and prevent distortion of structures during the other steps of preparation a. glutaraldehyde--forms cross linkages among protein molecules b. osmium tetroxide --cross links lipid molecules together 3. Dehydration—to prevent destruction when placed in vacuum alcohol washes then freeze-drying to remove all water; not necessary w/ light microscope 4. Slicing-necessary with light and T.E.M.--embedded in paraffin (light) or plastic resin (T.E.M.) then sliced very thin with an ultra-microtome OR 5. Coating-S.E.M. cover the surface with a 2-3 atom thick layer of gold or silver homogenization differential centrifugation supernatant pellet Would the presence or absence of a cell wall distinguish a prokaryotic cell from a eukaryotic cell? Binary fission Golgi apparatus Bound ribosomes make proteins that will be secreted from the cell Lysosome destroying worn-out organelles Some storage diseases such as Tay-Sachs are caused lysosomes that are defective. Plant cells have mitochondria too. Beating of cilia and flagella Movement of organelles, cytoplasmic streaming Anchors for the spindle fibers during mitosis. 9+2 9+0 Basal body anchor for cilia and flagella 9 pairs around 2 9 triplets around none microfilaments attach to microtubules and contract and pull on them Plant cells can grow longitudinally by adding more cellulose to their primary cell walls but cannot grow after forming their secondary cell wall. Extracellular matrix fibronectin Glycoproteins 95% carbohydrate Full Empty Contractile vacuoles nuclei actin actin Actin and keratin