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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 » Sun Apr 29, 2007 8:55 pm

krosey13 wrote:a colorimeter has to be used to make the plan of alevel standard otherwise it would be like GCSE cwk...


Or a haemocytometer can be used.

krosey13 wrote:the seperate solutiond have to be heated up to a constant temp befor they can be mixed together so that it makes a fair test, otherwise all substantces wont be of the same temp.


Why can't the sugar solution and yeast suspension be mixed then heated up together?

krosey13 wrote:in theory part u have to say how u need a pH buffer of 7-7.4 to maintain the pH and keep it constant.


You don't even need a buffer, so there's not an awful lot of point mentioning it; the pH can be kept constant without a buffer.
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Postby kjit » Sun Apr 29, 2007 8:56 pm

breifly what do you write in the scientific exp? a couple bullet points would be helpful. thnkz
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Postby Ulbrid » Sun Apr 29, 2007 9:14 pm

I wrote about how high temperatures cause enzymes to denature which, in turn, prevents yeast from respiring and stop converting glucose into ethanol. That was basically it.
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Postby kjit » Sun Apr 29, 2007 9:44 pm

thnkz for that.... :D
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Postby wannabeaditz » Mon Apr 30, 2007 10:09 am

krosey13 wrote:the seperate solutiond have to be heated up to a constant temp befor they can be mixed together so that it makes a fair test, otherwise all substantces wont be of the same temp.


Why can't the sugar solution and yeast suspension be mixed then heated up together?

they can't be mixed together before hand because then the solution will start to ferment
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Postby Ulbrid » Mon Apr 30, 2007 3:36 pm

wannabeaditz wrote:they can't be mixed together before hand because then the solution will start to ferment


So... what's your point? If the mixture does start to ferment, it isn't going to effect the results at all after heating because the heat will still denature the enzymes.
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Postby wannabeaditz » Mon Apr 30, 2007 5:55 pm

our teacher told us that if it ferments the solution will change it's concentration so it will no longer be a fair test
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preliminary work...x

Postby abikins » Mon Apr 30, 2007 6:58 pm

...could someone please help me with what prelimary experiment to do, or where to find an experiment previously done which i could relate to. any suggestions would be great!!

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Postby wannabeaditz » Mon Apr 30, 2007 7:17 pm

other people have asked this previously so you just need to read the last dew threads.
preliminary work you could do is finding what conentrations of solutions to use ettc
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biology plan

Postby Rubyredslippers » Tue May 01, 2007 9:48 am

I have just got this plan to do.....i am okay with it but before i have worked out these questions i cant get anywhere...please someone help me...it would be really really appreciated

Are we timing the experiment?
Whats yeast got to do with enzymes?
What i am supposed to write in my hypothesis?
What evidence/ scientific knowledge should i put in my hypothesis?

I think i am pretty much okay with the experiment, just not the writing up of it...

In answer to some of youre questions...the mehtylene blue turns colourless when the yeast has been killed and no colourimeter is needed as i doubt you need to be that accurate...the colour change is evidence enough i think
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Re: biology plan

Postby Ulbrid » Tue May 01, 2007 1:03 pm

Rubyredslippers wrote:In answer to some of youre questions...the mehtylene blue turns colourless when the yeast has been killed and no colourimeter is needed as i doubt you need to be that accurate...the colour change is evidence enough i think


It's actually the other way around: methylene blue turns colourless when the enzymes in the yeast are active, and it's blue when they are inactive.

Rubyredslippers wrote:I have just got this plan to do.....i am okay with it but before i have worked out these questions i cant get anywhere...please someone help me...it would be really really appreciated

Are we timing the experiment?
Whats yeast got to do with enzymes?
What i am supposed to write in my hypothesis?
What evidence/ scientific knowledge should i put in my hypothesis?

I think i am pretty much okay with the experiment, just not the writing up of it...


It' best to keep the duration for each experiment constant. Say, around, 10 minutes or so.

The enzymes in the yeast get denatured at high temperatures which halts metabolic reactions from occuring and the conversion of glucose (or whatever sugar solution you use) to ethanol.

I haven't really done a hypothesis. Instead, i've done background information in which i've described how heat affects enzyme action etc., and a prediction where i've just stated what temperature i expect all of the yeast cells to be dead.
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Re: biology plan

Postby wannabeaditz » Tue May 01, 2007 3:51 pm

Ulbrid wrote:
Rubyredslippers wrote:In answer to some of youre questions...the mehtylene blue turns colourless when the yeast has been killed and no colourimeter is needed as i doubt you need to be that accurate...the colour change is evidence enough i think
It's actually the other way around: methylene blue turns colourless when the enzymes in the yeast are active, and it's blue when they are inactive.


are you sure its the other way around
in my preliminary work the meth blue turned colourless when the yeast died
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