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The effect of temperature on the survival of yeast cells

Debate and discussion of any biological questions not pertaining to a particular topic.

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Postby blcr11 » Fri Apr 27, 2007 8:09 am

I'm not going to argue with you too much about the haemocytometer. I am curious to know what you think you're going to see. My guess is that, for the most part, the cells will look like the background color of the solution. I suppose if you are very close to the temperature where all the enzymes are dead, you might possibly see a few cells that are decolorized a little more compared to the background, but I suspect that will be a fleeting thing and hard to catch and maybe even hard to distinguish from the birefringence of the cells--but you're welcome to try.

And at what wavelength are you choosing to do the colorimetry? Your reference samples should be fine, and if you choose a good wavelength you should be able to put the amount of decolorization on some sort of curve, although to do it "properly" would require some intermediate points, as well. You can always assume linearity. I would encourage you to let the cells settle before taking the measurement otherwise you will have trouble with light scattering off the yeast cells. I still think you won't be any more accurate than just using the old eyeball. I can always be wrong, though.
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Postby Ulbrid » Fri Apr 27, 2007 11:04 am

blcr11 wrote:I am curious to know what you think you're going to see.


When carrying out a preliminary experiment, the dead cells (bright blue) were easily distinguishable from the living cells (colourless with a darker outline). Mind you, i was using a normal slide and not a haemocytometer but this shouldn't make any difference.

To be honest, as long you your method is justified, it shouldn't really matter which option you chose; i'm sticking with using a haemocytometer since it should give the most accurate results, which is a reason easiliy used to justify its use.
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Postby blcr11 » Fri Apr 27, 2007 11:40 am

Hey, if it works, it works!
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Postby baby_jojo » Fri Apr 27, 2007 4:44 pm

whats the suspension of yeast mean?
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Postby Nagini » Fri Apr 27, 2007 5:12 pm

baby_jojo wrote:whats the suspension of yeast mean?


Because yeast cannot dissolve in water since it is a living thing, it's called a suspension not solution.

(( I'm doing this plan too and it seems too difficult. Im really not looking forward to the practical exam now lol ))

Edit: ________________________

Also it will be easier to use glucose instead of sucrose (and say this in you're plan) because sucrose is a disaccharide so the yeast has to convert it to glucose. It doesn't do anything else but the experiment takes longer.
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Postby broadbelly » Fri Apr 27, 2007 7:42 pm

i rekons we all read into the experiment too much. cos thers lods of stuff u cud do 2 make it proper, i.e. colorimeters and haemocytometers and crap, but as soon as u start gettin beyond ur kinda basic level of equipd and wat not u know ur finking too deep, so basicaly i fink al tehr looking 4 is a nice simple method of looking at the color.
oh and did any1 ese ee that they put "rapid temperature change" in, as iff too say that the rate of temperature change is as bad as high temperatures itself?
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Postby 01addiv-llangirb » Fri Apr 27, 2007 8:08 pm

Hi,

This is the second big post on this go into cell biology and there is one there (12 pages).

I like this experiment as there is plenty of scope on what to do and found that me and my class all went wow how shall we do this?

For a slight take on method I used a method similar to what Ulbrid describes, but i only stain the cells once they are on the slide. 1 drop from a teat pipette and one drop of methylene blue showed the difference really well (50C showed some alive some dead).

I see no reason to worry about Ph as you should use the same solutions all the way through and the question does not mention. I can think of no good reason to worry about which sugar you use so long as you have no intention of describing glycolosis in great detail.

Does anyone know which specific enzyme methelyene blue affects?

If you use information from here you are supposed to declare it in a bibliography/list at the back - which is not included in the word limit. (by the way generally you have 10% leeway on the word Limit)

Check the other post and good luck.
Physics more and more knowledge about less and less. - Still it's the basis for all else.
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Postby *biologist* » Sat Apr 28, 2007 9:14 am

why must we keep the volume of yeast suspension constant?
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Postby baby_jojo » Sat Apr 28, 2007 9:51 am

Nagini wrote:Because yeast cannot dissolve in water since it is a living thing, it's called a suspension not solution.


So if i evaporate the water of the suspension of yeast i would be left with dried yeast particles!

do we add the glucose solution to the yeast suspension or yeast particles?
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Postby baby_jojo » Sat Apr 28, 2007 9:53 am

*biologist* wrote:why must we keep the volume of yeast suspension constant?


i presume it's to keep the test fair! if we used a different volume of yeast suspension we could be using a different amount of yeast making our experiment an unfair test
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Postby Ulbrid » Sat Apr 28, 2007 10:21 am

baby_jojo wrote:
Nagini wrote:do we add the glucose solution to the yeast suspension or yeast particles?


We get given (well actually we don't) a suspension of yeast, so the glucose/sucrose solution is just added to that.
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Postby sarah briggs » Sat Apr 28, 2007 2:31 pm

Does any one know why the Enzymes from the respiring yeast cells cause Meth Blue to become colourelss (the actual scienific reasoning), My teacher hinted that ions where involved??
Thanks
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