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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 Ulbrid » Wed Apr 25, 2007 7:08 am

Unless the yeast suspension is really dilute, using a colorimeter isn't going to work. I think the best way would be to use a haemocytometer and count the cells.

Seeing as we never actually have to carry out this experiment, would there be any harm in using 1 degree Celcius increments and carrying out the experiment 5 times for each temperature to get an accurate average (hypothetically, that is)?
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Postby danii-jo » Wed Apr 25, 2007 8:03 am

broadbelly wrote:dya rekon we'd all b screwed if examners found out about this?



well if my teacher found this site in bout 10 mins then i think that the examners will no bout this!! :P
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Postby danii-jo » Wed Apr 25, 2007 8:08 am

ulbrid
i agree with using the haemocytometer, and also that is a good point to make bout us not doin the experiment so what harm is it by doing things that will take a while, we have been told to include as many repeats as we can nd take an average! like u said!!
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Postby Jacob » Wed Apr 25, 2007 8:57 am

I can't find anywhere on the internet showing the rough temperature range that yeast is killed. It seems that the researchers aren't really interested in what temperature the yeast is killed but the other properties of it. I found a temperature range on a baking site which says that most of the yeast is killed between the ranges of 55-60C (quite a bit higher than body enzymes).
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planning exercise

Postby emo-lady » Wed Apr 25, 2007 9:44 am

im a little confused over which temperature the question is asking for. does it mean the lowest temperature that kills yeast, eg. 4c may kill yeast, or the lowest high temperature, eg. 40c moght kill yeast. which end is it looking for? help!
thanks
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Re: planning exercise

Postby Ulbrid » Wed Apr 25, 2007 11:02 am

emo-lady wrote:im a little confused over which temperature the question is asking for. does it mean the lowest temperature that kills yeast, eg. 4c may kill yeast, or the lowest high temperature, eg. 40c moght kill yeast. which end is it looking for? help!
thanks


It's asking for the lowest temperature at which no yeast cells survive. So, if using a haemocytometer, you need to find the lowest temperature at which all of the yeast cells you see under the microscope are blue (i.e. the first temperature which you see no colourless cells).

What's the word limit for this plan? I was told 1000 words, but mine is already 2000+ :(
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Re: planning exercise

Postby danii-jo » Wed Apr 25, 2007 11:41 am

Ulbrid wrote:
emo-lady wrote:im a little confused over which temperature the question is asking for. does it mean the lowest temperature that kills yeast, eg. 4c may kill yeast, or the lowest high temperature, eg. 40c moght kill yeast. which end is it looking for? help!
thanks


It's asking for the lowest temperature at which no yeast cells survive. So, if using a haemocytometer, you need to find the lowest temperature at which all of the yeast cells you see under the microscope are blue (i.e. the first temperature which you see no colourless cells).

What's the word limit for this plan? I was told 1000 words, but mine is already 2000+ :(


its askin for the lowest of the highest, so anything over 35C as thats yeasts opt temp so over that but the lowest over that!! :)
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sucrose/glucose

Postby abcdef » Wed Apr 25, 2007 12:55 pm

does anyone kno if it make a difference whether you use sucrose or glucose??

thanx
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Re: sucrose/glucose

Postby Ulbrid » Wed Apr 25, 2007 1:59 pm

abcdef wrote:does anyone kno if it make a difference whether you use sucrose or glucose??

thanx


It doesn't really matter but, for what it's worth, i've going to (hypothetically) use sucrose.

Is everybody else finding it difficult keeping to the word limit?
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Postby broadbelly » Wed Apr 25, 2007 4:33 pm

ye i fink the key on the word limit is to hav loads of diagrams and stuff with lables and stuff which dont count 4 the word limit, im wel over 1000 but twil b fine
this haemocytometer seems pretty pointless to me cos thers buns of room 4 human error and generally takes loads of time, and it ses use "school lab" resources and i duno about u but we dont hav any haemocytometer things.
and i herd from sum physics nerd that the densnes of the yeast wud still transmit more light that the blue, and hes one of them trust worthy oxbridge kinda kids so u know ur safe ther :wink:
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I AM SOOO CONFUSED WITH THIS STUPId bio COURSWEORK :s

Postby funky pisces » Wed Apr 25, 2007 8:40 pm

OK IM STUK ON LYK QUITE A FEW THINGS SO IF THERE IS ANY1 OUT THERE WHO COULD HELLP ME BEFORE MY DEADLINE ON MONDAY the 30th if april ID BE SOOOOOOOOO GREATFUL,

1) can anyone tell me what we have to write in the prediction.like should it just b a statement or a whole paraagraph?

2) in our conclusion what should we write? like how would you write about analysing your results and presenting them?

thankxxxxxxx
funky pisces xxx
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Postby broadbelly » Wed Apr 25, 2007 9:11 pm

to Funky Pisces

wiv teh prediction u gota say wat temp u think will cause th edeath of all yeast cells and why u fink so, quote from a source sumwer, type "yeast temperature" on google and the 1st thing, summit about newton, shud give a gd rough estim8 u can use as a quote


with the conclusion just say wat ur results tell ya, i.e. say u give a made up result that at 60dC ur mixture turns blue, then at that temperature cos its blue, it means the yeast cells die. make sure u quotre from ur own results.

i fink tho, im a lil bit lost, iv bin bumming on about colorimters 4 ages and now im quikly giving up on anything complicated and just goin 4 wat i can see in the test tube lol, simples often the best i suppose
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