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effect of temperature on the survival of yeast cells

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Postby <Singing Mice> » Fri May 04, 2007 6:17 pm

Foo wrote:Any more pointers you guys want to give me?

i just got this plan this week so it would be pretty handy. For example what IS the temperature that kills all the yeast cells? And what's better, microscope and colorimeter?

Cheers for the help so far :)


First of all, would that be 'foo' for the legendary band that is the foo fighters? if yes, there my fave band so woohoo!
Um, microscope or colorimeter? Well the colorimeter will tell you the exact amount of light that is being transmitted through the solution (100% would be a perfectly clear solution so the cells would all be alive, 40%ish would mean they were all dead [ive been told]) but if you have a good eye for colours a microscope could be ok, but a colorimeter is more accurate. Got any tips of your own? :)
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Postby Ulbrid » Fri May 04, 2007 8:31 pm

<Singing Mice> wrote:Oh, another thing- make sure you mention that methylene blue actually inhibits the respiration of of yeast, as it picks up the hydrogen ions produced during the process. the yeast cannot then use the ions to make energy. this could have a confounding effect on your results :)


Thank you for that, i'll go add that now! :)
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Postby Ulbrid » Fri May 04, 2007 8:40 pm

<Singing Mice> wrote:Um, microscope or colorimeter? Well the colorimeter will tell you the exact amount of light that is being transmitted through the solution (100% would be a perfectly clear solution so the cells would all be alive, 40%ish would mean they were all dead [ive been told]) but if you have a good eye for colours a microscope could be ok, but a colorimeter is more accurate. Got any tips of your own? :)


The problem is: the solution won't be perfectly clear since the yeast suspension is cloudy. In fact, it would be difficult to get any kind of reading because i doubt any light will be transmitted through the solution (unless heavily, and accurately, diluted).

Therefore, i think using a microscope is more accurate because you can count the individual blue and colourless yeast cells and calculate percentages of living/dead cells.
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Postby sroberts88 » Sun May 06, 2007 11:58 am

I'm a little bit confused I've written all about enzymes in my background info part and I've just reallised I haven't mentioned yeast, where so enzymes come in to the fermentation of yeast? I know this is a stupid question but I've just confused myself thoroughly!
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Postby sroberts88 » Sun May 06, 2007 12:03 pm

and it says that kills all yeast cells, yeast is a fungi not an enzyme so what has the enzymes being denatured got to do with the yeast cells dying? Anyb help on this would be greatly appriciated.

Also how accurate do we have to be with the temperature? I've done every 5 degrees and said in my limitatioss that id I had more time I would have done 1 degree increments, is that alright do you think?
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Postby blcr11 » Sun May 06, 2007 12:36 pm

If you destroy the enzymes the organism needs to survive, have you not effectively "killed" them.

The accuracy of the result should be limited by how fine a temperature grid you sample; the finer the grid, the more accurate the result, in principle.
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Postby sroberts88 » Sun May 06, 2007 1:05 pm

yeah that makes sense thanks.

Don't think I've used a temperature grip, I've put boiling tubes in water baths from 50 degrees up to 70 degrees at 5 degree increments.
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Postby sroberts88 » Sun May 06, 2007 1:09 pm

oh and one more thing, anyone know the size or grid I should be using in my haemocytometer slide?
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Postby Prija25 » Sun May 06, 2007 2:15 pm

does anybody know why the volume of yeast should be kept constant/how it affects the experiment. All i can think of is that they will take different times to heat up to the correct temperature :?
thanks
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Postby Foo » Mon May 07, 2007 11:46 am

First of all, would that be 'foo' for the legendary band that is the foo fighters? if yes, there my fave band so woohoo!
Um, microscope or colorimeter? Well the colorimeter will tell you the exact amount of light that is being transmitted through the solution (100% would be a perfectly clear solution so the cells would all be alive, 40%ish would mean they were all dead [ive been told]) but if you have a good eye for colours a microscope could be ok, but a colorimeter is more accurate. Got any tips of your own? :D


hmm
one of those haemocytometer slides is what my teacher said to use and then calculate the percentage that are dead or alive (dead would be blue, alive would be clear). Would a colorimeter work because the liquid would still have the yeast solution in and so would never be actually clear. or am i just having a blonde monent??

And also, I'm not named after the Foo Fighters, it's just what a handful of my friends call me. how odd. but i am also a fan of said band so yay!

xxx
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Postby sroberts88 » Mon May 07, 2007 11:52 am

Yeah I tried using a colorimeter in my prelims and it didm't work because the solution was too cloudy so I said that in my plan I think the haemocytometer is the best option by far because with a normal microscope slide it is difficult to count the same size area for each sample.

Does anyone know if there is one of these forums for the A2 practical as I'm doing them both at the same time and the A2 one is HARD! x
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Postby Tifa » Mon May 07, 2007 2:45 pm

Hmm can none of you do this yourselves without having to ask the same questions over and over. Its part of your exam so do some research otherwise its plagiarism. A little bit of help is alright but noone wants to do your work for you.
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