microscopy and differential staining Essay

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1.What are the advantages and disadvantages of the different types of light and electron microscopes discussed in Chapter 3 that are used to study microorganisms? Focus your response in terms of the following parameters:
◦Range of magnification
◦Resolving ability
◦Sample preparation
◦Possible states of sample (e.g. whole organism, part of, living, non-living, etc.)
2.What type of microscope would you use to investigate each of the following scenarios and why (your answer to question 1 will help):
◦Determine the relative sizes of two eukaryotic cells.
◦Determine how many bacteria are dying after a chemical treatment.
◦Determine where in a eukaryotic cell a particular protein is localized.
◦Identify a virus from a contaminated
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-not necesary to fix or stain specimen.

-internal structures of a cell more sharply defined

-Electron Microscopes: Beam of electrons used instead of light.

-Objects smaller than 2.0μm such as viruses must be examined with this type of microscope-resolving power much greater because wavelength of electrons is 100,000 times smaller than the wavelengths of visible light.

-images are always black and white, but they can be colored to accentuate certain details

-use electromagnetic lens instead of glas lens used by light microscopes

- two types of electron microscopes:

Transmission electron microscope : -Can resolve objects as close as 1PM and objects are generally magnified 10,000 to 100,000X.

-only very thin section of specimen can be studied effectiviely. Thus specimen has no three-demensional aspect.

-specimens must be fixed , dehydrated andviewed under high vacuum to prevent electron shattering and these treatments not only kill the specimen,but also cause shrinkage and distortion.

Scanning Electron Microscopy :-overcomes the problem of sectioning associated with transmission electronmicroscope

-striking three dimensional views.

-especially useful in studying the surface structures of intact cells and viruses

-resolves
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