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Light microscopes

  1. Oct 27, 2008 #1
    can a light microscope with 1000x magnification see clearly a unicellular organism moving around and feeding and stuff like that. And if not would u need an electron microscope?
     
  2. jcsd
  3. Oct 27, 2008 #2
    For protists this is plenty. Also, sample preparation for electron microscopes kills your cells. It is purely a visualization technique but does not allow to monitor dynamics or processes. At least not with the given sample. One could capture a series of different samples, of course.
    The only technique that gives nm resolution and allows the cell to continue living is (to my knowledge) AFM. But it usually takes a couple of minutes (usually 5-15 min, depending on scan speed) to get images with good resolution.
     
  4. Oct 27, 2008 #3

    mgb_phys

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    Can you get 1000x without oil immersion?
    Would oil immersion be a problem for your sample
     
  5. Oct 27, 2008 #4
    There are also 100x water immersion objectives. Though it should not make much of a problem for the sample per se. The only factors between oil and water are (besides price) aperture and the requirement for lens correction.
    If that is not a problem water immersion are so much easier to keep clean. Especially if you are not the only user.

    Ow, forgot to add, water immersion also has the added advantage of being able to focus deeper into the sample, if it is mounted in water.
     
  6. Oct 27, 2008 #5
    well the one lense is 10x and the other 100x for a total of 1000x right?

    also what are the steps for getting a slide to view that can hold some water, paramecium, and some algae for feeding, would it have to be a cube like slide instead of so flat?

    and are there any prokaryotic cells that are big enough to see under a light microscope with this kind of magnification?
     
  7. Oct 27, 2008 #6

    Moonbear

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    Yes, the standard magnification for ocular lenses is 10x, and then we were assuming that meant you were using a 100x objective lens.

    You might be able to manage with a regular wet mount on a plain glass slide (just make sure it has no special coating that would make the specimen stick on it). Otherwise, you can get slides with shallow wells in them that will be plenty sufficient.
     
  8. Oct 27, 2008 #7
    ok sounds good, thanks for the help.
     
  9. Oct 27, 2008 #8

    Andy Resnick

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    I'd like to clear up a possible confusion on this thread- the resolving power of a microscope (or any optical system) is given by the numerical aperture, not the magnification. If one used a 100X NA = 0.001 objective lens, all you would see are blurry blobs, and maybe not even that. One could use a 20X NA1.2 water objective and could (probably) see protists by using secondary magnification. The rule of thumb is that any magnification beyond 1000X the numerical aperture is "empty", meaning no additional detail will be revealed at higher magnification.

    But to answer the OP, a high-quality 100X immersion (NA 1.2 - 1.4) objective will provide a optical resolution limit of about 0.2 micron. Use of EM, as Charion states, is not possible for living matter.
     
  10. Oct 27, 2008 #9

    Ygggdrasil

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    Since it hasn't been mentioned yet, most prokaryotic cells have dimensions on the order of one micron, so they are clearly above the resolution limit of optical microscopy. Eukaryotic cells will be larger.

    Being able to see unicellular organisms is not just a matter of resolution, however. Many unicellular organisms are transparent and not easy to visualize directly. Thus, you need some way produce contrast. One simple method is staining, but this is often not the best choice for living samples. You can, however, create contrast by methods that make use of the diffracted light from the sample (dark field microscopy) or the fact that your sample has a different index of refraction than the surrounding material (phase contrast microscopy or differential interference contrast microscopy).
     
  11. Oct 28, 2008 #10
    oh ok, wow thats a lot of info lol. Thanks for all the help.
     
  12. Oct 28, 2008 #11
    so what is used to view the inside of a cell in detail such as enzymes and other cool things happening while the cell is still living and functioning normally since EM will kill it.
     
  13. Oct 28, 2008 #12
    Simply put: there is no such instrument. With fluorescence tagged proteins you can visualize their localization, for instance, but there is no way for direct high resolution imaging of enzymatic activities within a living cell. One could do single molecule interactions with an AFM, but one would be limited to cell surfaces. Moreover, these kind of measurements are kind of tricky often not very reproducible so that it is usually limited to in vitro systems.
     
  14. Oct 28, 2008 #13
    so how do they know how all that stuff actually works inside a nucleus of a cell while its living and functioning without being able to see it happen?
     
  15. Oct 29, 2008 #14

    Monique

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    By making mutations in the genes of interest and looking at their phenotypes. In addition, in vitro work can be very informative. Think for instance about assays where you determine whether proteins are able to bind each other.

    To add to Charion's comment: you can also use a technique named FRET (fluorescence resonance energy transfer), if two labeled molecules come in close proximity to each other you get the energy transfer and fluorescence.

    Are you interested in bacteria for any particular reason? They are really small, it is easier to study eukaryotic cells.
     
  16. Oct 29, 2008 #15
    Well...If you happened to have one at your disposal...an Environmental SEM operating in Wet mode does let you view biological samples without killing them. We have put living flies in ours and they survived for quite a while. You can get insane resolution and contrast without needing to sputter coat anything. All you need is about half a million bucks to buy one!
     
  17. Oct 30, 2008 #16
    You can observe eukaryotes at that magnification, most of them are large enough. You take a glass slide, put the cell in water with a dropper, then put a thin glass slide called cover slip.
     
  18. Oct 30, 2008 #17
    ok, is paramecium a eukaryotic cell? because it is single celled and seems quite interesting? are things like cancer cells and other things big enough to see under light microscopes or do you need something more powerful?
     
  19. Oct 30, 2008 #18
    I have no background in biology...but isn't a cancer cell just basically a regular cell that is programmed incorrectly so that it multiplies uncontrollably?

    I can see erythrocytes quite well at a relatively low magnification on an optical microscope. They are very dilute - about 1 drop of sheeps blood to 7 mls of saline solution.
     
  20. Oct 30, 2008 #19

    Ygggdrasil

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    I've looked at human cancer cells under a relatively cheap microscope before. They are definitely big enough to see.

    And, yes, a cancer cell is a regular cell that has undergone mutation that allow it to divide indefinitely.
     
  21. Oct 31, 2008 #20
    so does cancer just infect ur good cells in lets say ur lungs by injecting faulty dna that makes them reproduce uncontrollobly causing tumors which screw up surrounding organs?
     
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