01-16-08, Chapter 7

01-16-08, Chapter 7 - January 16, 2008 Structure and...

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J anuary 16, 2008 Structure and Function of Microscopes The compd light microscope has 2 lenses -objective lens -eyepiece, ocular Magnification power -eyepiece=10X -Objective lenses (10x-40x and 100x9in oil immersion)] The total magnification power -the product of the two lenses -the max mag of light microscope is 1000X Resolving power (aka resolution) -ability of optical system to produce detailed image -expressed as the minimal distance btw 2 points that can be distinguished -naked eye about 0.2 mm resolution -what is the resolution of a light microscope a thousand better than 0.2mm=0.2um -can you see virus w/light microscope? NO 4.1 Why oil? -Oil has higher refractive index. -allows the objective lens to be brought closer to the specimen increase resolution. Preparation of specimen for light microscope 1) Wet mount 2) Smear preparation, fixation and stained -Negative stain Dye does not stain cells Dye stays in the background Positive Stain (simple stains) -Dye stains cells -One dye (simple stain) Q: Most cell surface molecule, are neg. charge Confocal scanning microscope A confocal scanning microscope illuminates the specimen with a laser bean similar to fluorescence microscope. Cells stained with fluorescent dyes Multiple plane images are assembled by software to form 3-D images [it can be used to measure neuronal growth when neurons are kill? Fig 4.11 Fig 4.13 Transmission Electron microscope [ know differences between light and electron microscope The light microscope Use light rays, can penetrate cells 0.2 um resolution [can be used to view prokaryotes and eukaryotes [can even view viruses Electron microscope Use electron beams, weak in penetration 0.2 nm resolution [can clearly view viruses [is a useful tool to view small cells Fig 4.15
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Fig 4.14(b) Transmission electron microscope (TEM) [weak penetration, therefore need a very thin sample TEM requires a thin section (has to be ____) of cells stained with heavy metal Application: observation of internal cell structure [does not have good electron absorbing power. Fig 4.16 Fig 4.14 (c) Scanning Electron microscope [nothing penetrates through specimen Specimen need to be coated with noble metal e.g. gold SEM has a greater depth of field than TEM— image is 3-D Application: cell surface analysis, cell [cell interactions Fig 4.17 AtomicroscopeForce Microscope (AFM) Scanned by a probe Resolution of 0.05 um 3-D images of cells and surface structure Cells can be image alive (Does not require coating) Fig Cell morphology Fig 4.21 [cocci, clustered cocci (random direction), paired cocci, and chained cocci Fig 4.23 Bacilli can form chains, pairs, Fig 4.22 Fig 4.24 (a) (b) [causes ulcers, h. pylori Fig 4.28 Mycelial Bacterium Fig 4.27 Filamentous bacteria (Cyanobacterium, produces O2 from Photosys) Microbial Community[Biofilms Sometimes work as a team to cause infection; biofilms form by sugar? capsule? Community? Size of Bacteria and Achaea
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01-16-08, Chapter 7 - January 16, 2008 Structure and...

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