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Ch. 8 + 9 - Review of Cell Structure Introductory lecture covering cellular structure and cell visualization.

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BIOL 2021
Julie Clark

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Biol 2021- January 4, 2011  Review cell structure (chapter 8 & 9)  Visualizing cell (chapter 9) Bacterial cell  NO INTERNAL MEMBRANE- prokaryotes only have plasma membrane  Bacteria have cell wall, cell membrane, ribosomes and enzymes inside Eukaryotes - Yeast - Internal membranes in organelles - Everything has a membrane - Cell walls- bacteria, plants, fungi are all different - Vacuole: major storage organelle in plant Visualizing cells 1) Light microscope  Bacteria and mitochondria are usually smallest objects whose shape we can discern in the light microscope  Transmits visible light through specimen  Bright field (full light spectrum): normal light microscope in which the image is obtained by simple transmission of light through the object being viewed 2) Phase contrast  Can see living cells  No need for stain; transparent cells become visible  4 types of light microscopy-(A) bright field microscopy, (B)phase-contrast, (C) Narmarski differential-interference-contrast microscopy, (D) dark field microscopy 3) Stain cell  Involves killing cells, slicing thin cells and staining them  Sliced cells are treated with a fixative and then embedded in a supporting medium before sectionin.  Cells are usually invisible under ordinary light microscope, so they often must be stained with organic dye that have a specific affinity for particular subcellular componenets- different stains for different components Figure 1 Staining of cellular components. Urine collecting ducts in kidneys- nuclei stained in red; extracellular matrix in purple 4) Florescent probes  Specific molecules can be located in cells by fluorescence microscopy  Fluorescent molecules absorb light at one wavelength and emit it at another longer wavelength  Using a fluorescent microscope- it illuminates a compound at its absorbing wavelength and then view it through a filter that allows only light of the emitted wavelength to pass, it will glow against a dark background (uses 2 filters)  Disadvantages- excited only by a certain light of certain wavelength and fade fairly fast when continuously
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