ronke95
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I'm starting sixth form in september and my sixth form have given me homework to complete, they've asked me question I've never encountered or studied before and I really need help answering a question as I have not found a straightforward answer online.

Q - Describe how you would prepare a temporary mount (e.g. onion epidermis) for light microscopy.
Give reasons for each step in the procedure, e.g. for having a thin sample, using a stain, using the lowest power objective lens first. [8marks]

Any help would be appreciated or any notes on the whole topic of microscopy, thanks!!


I've completed the rest of the questions but would really appreciate a second opinion if anyone wouldn't mind helping ~

Q ~ Describe the advantages and disadvantages of electron microscopy to study cell ultrastructure. [8 marks]


Q ~ Sort these statements into 3 lists: Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Both.

  1. Electrons are absorbed by heavily stained parts.
  2. A 3-D image is obtained.
  3. Electrons are reflected from the surface of the specimen.
  4. Electrons pass through the specimen.
  5. Specimen is stained using a heavy metal stain.
  6. An image of a section through the specimen is obtained.
  7. An image of the internal structure is obtained.
  8. An image of the whole specimen can be obtained.
Can be used to obtain images of viruses and large molecules

Q ~ Write about the importance and function of mitochondrial DNA
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linkdapink
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http://www.biologymad.com/master.htm...ells/cells.htm

That might help a bit! I can't remember microscopy, and I'm rubbish, but I used that a lot once upon a time
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ronke95
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Was just using that site for some of the other questions, unfortunately it doesn't really help answer my first one
Thanks for the suggestion!
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Eloades11
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It's basically asking how do you use a microscope, so upon searching youtube I found this http://www.youtube.com/watch?v=jP9HtcAvGDk

You have a thin sample so layers don't overlap with each other and blur the image. In some cases you may use a stain in order to be able to see the artefact you're looking for, may this be bacteria or in your case, onion epidermis. You should always use the lowest power objective first as protocol to prevent damaging the slide/specimen or the micoscope, and it is easier to locate the sample you're trying to find.
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ronke95
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Thanks, really helpful!
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ronke95
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Juicy mango97
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Ok I’ll write it in exam answer form 1) the onion root tip should be cut from the tip as this is where mitosis is taking place2) put the onion root in hydrochloride acid to break down the cell walls / membranes so stain can reach chromosomes 3) after 5 mins take out and place in distilled water to remove hydrochloric acid and then use stain to stain chromosomes so they can be seen in optical microscope4) macerate the tissue with a mounted needle so the cells are not conjoined and break up the cells5) carefully place a cover slip on top with filter paper to absorb excess dye and push hard to make tissue thin roughy for light to be transmitted and don’t push sideways do chromosomes do not get damagedThats the basic explanation
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Theloniouss
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(Original post by Juicy mango97)
Ok I’ll write it in exam answer form 1) the onion root tip should be cut from the tip as this is where mitosis is taking place2) put the onion root in hydrochloride acid to break down the cell walls / membranes so stain can reach chromosomes 3) after 5 mins take out and place in distilled water to remove hydrochloric acid and then use stain to stain chromosomes so they can be seen in optical microscope4) macerate the tissue with a mounted needle so the cells are not conjoined and break up the cells5) carefully place a cover slip on top with filter paper to absorb excess dye and push hard to make tissue thin roughy for light to be transmitted and don’t push sideways do chromosomes do not get damagedThats the basic explanation
I'm afraid this thread is 8 years old.
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