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Osmosis and Diffusion

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Osmosis and Diffusion

Postby jsmith613 » Sun Jul 26, 2009 11:08 am

Dear Community,

Please could someone describe an experiment to show Osmosis and Diffusion on LIVING organisms.
(I have experiments for non-living organisms - but my syllabus also requires that I know some experiments for living ones as well)
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Postby Darby » Sun Jul 26, 2009 2:08 pm

I do one with Elodea leaves and saturated salt solutions that works pretty well. The fresh-water aquatic cells are very permeable to water but not so much to the ions, so the cells shrink from osmotic loss. It's simple, easy to set up and for the students to see, and I can even kind of force them to figuring out what's happening (although you have to say, "DON'T blame the salt!!!!" many many many times).
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Postby freshbiology » Sat Aug 01, 2009 4:25 pm

You can also try skin (epidermis) of fleshy scales of onion. Easy to get. Just peel off a piece. Place it in a drop of water on the slide. Keep it expanded..i.e make sure it is not folded. Add a couple of drops of salt solution..say 10% potassium nitrate. You get result instantly. Exosmosis will take place. Demonstrate and then wash with pure water to show osmosis or end-osmosis. Now water moves into the cells. So with just a couple of steps you can show it to your students both water moving out and into the living cells.
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Re: Osmosis and Diffusion

Postby Vsalazar » Wed Oct 07, 2009 7:22 pm

You sound really smart, and I liked what you said. :D
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Postby JackBean » Thu Oct 08, 2009 5:44 am

Or you can use also a little of blood and watch the red blood cells, which are quite used example for these experiments ;)
Also, we have been watching plastids in some moss or something, I don't remember the name, now. Anyway, the plastids are moving around in the cytosol.
http://www.biolib.cz/en/main/

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Postby jwalin » Tue Oct 13, 2009 8:05 am

onion cells and red blood cells are very good ideas.
i have done these xexperiments about a year or a 2 back work well.
you can also plasmolysis.
try finding out at what conc a cell becomes incepient plasmolysed.
it isn't what you do that matters but it is how you do it
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Postby jwalin » Tue Oct 13, 2009 8:05 am

in an animal also try seeing at what concentration would it burst.
use the cheek cell and compare at what conc the cells burst.
it isn't what you do that matters but it is how you do it
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Postby JackBean » Tue Oct 13, 2009 8:12 am

This isn't much about osmosis, more about differences between plant and animal cell, but you could also pick some plant cell with cell well (or some yeast or something) and some animal cell (like the red blood cell) and compare, what will they do in hypo- and hypertonic solutions ;)
http://www.biolib.cz/en/main/

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Postby jwalin » Tue Oct 13, 2009 8:23 am

i just tried to make things interesting and a little complex.
to increase the complexity he could also plot a standard curve for different cells.
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