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effect of temperature on the survival of yeast cells

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Postby Doive » Mon Apr 16, 2007 5:12 pm

wassup wrote:im doing this at the moment too.

for your plan how long did you say you were going to leave the methylene with the yeast?

please help


The methylene is the indicator, you put a few drops into the yeast before you add the sugar solution. You don't have to leave the yeast and the methylene for a certain time, just mix them together. In my plan I add the sugar soulution to the yeast then leave it for 5mins to see if the colour changes. Also, the only way to get a graph of your results is to use a colourimeter, which measures how much light passes through a sample of liquid.

Anyway, you mix the methylene with the yeast, you don't have to leave the two together for any period of time
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Postby tallboy101 » Tue Apr 17, 2007 8:47 am

I'm considering using a haemocytometer and microscope to physically count the number of yeast cells remaining stained at each selected temperature and using with the results plot a graph and use a line of best fit. But i'm concerned that the yeast's enzyme for anaerobic respiration should all cease to work at the same temperature. Using a colorimeter wouldn't you get the same sort of problem i.e no gradual colour change?

Any ideas on this?
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Postby Classified Information » Tue Apr 17, 2007 12:04 pm

Is this for the open book exam in AS Biology by any chance? I got given mine today, and it is exactly what's been described.
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Postby The pink fairy » Tue Apr 17, 2007 6:19 pm

wassup wrote:im doing this at the moment too.

for your plan how long did you say you were going to leave the methylene with the yeast?

please help


Hi i've just been given this too I;m probably going to leave it at the most 5 minutes.

What have you done for your prediction?

I really need your help!!!
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Postby Doive » Tue Apr 17, 2007 6:46 pm

Classified Information wrote:Is this for the open book exam in AS Biology by any chance? I got given mine today, and it is exactly what's been described.


Yes, yes it is.
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Postby flyingbarbie » Tue Apr 17, 2007 7:33 pm

does the methylene blue have to be heated to the same temperature as the sugar/yeast solution before it can be added?
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Postby Doive » Tue Apr 17, 2007 7:40 pm

you get cold yeast suspension....add a few drops of the methylene blue.....mix it together, it's now blue. You put this mixture into a water bath at whatever temperature you want it at for about 10mins. You then take out the yeast suspension. Then you add the sugar solution to the yeast and see if the blue colour changes. If the blue colour disappears or starts to disappear, there are still yeast cells that haven't been denatured. Is this clear?? If the blue stays as it is, the enzymes are not functioning, which means they have been denatured by the heat.

There seems to be lots of confusion surrounding the methylene blue. It is an indicator, you only add a few drops of it. You mix it into the yeast, you don't add them together and then leave them for 5 mins, you mix them. Add it before you heat the yeast, otherwise it will cool the yeast down.

DOES EVERYONE UNDERSTAND?!!!
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hi could anyone help

Postby MIKKI020490 » Wed Apr 18, 2007 8:50 am

hi i am doing this years plannign exercise and i am really stuck its about the effect of tempreture on yeast enzymes could anyone help please
xxxx :D
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microscope

Postby fhsen » Wed Apr 18, 2007 9:59 pm

to the person who wanted to use the microscope, wouldnt that mean that you didn't need to use glucose at all, because if you use a microscope to see which cells have been stained won't the glucose get in the way?? im very confused about that because that is what i wanted to do
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Postby tallboy101 » Wed Apr 18, 2007 11:40 pm

You need a sugar to see whether the yeast is respiring. I very much doubt you'd see a molecule as small as glucose under a light microscope.

Has anyone found roughly the temperature that the enzymes for respiration IN YEAST becomes denatured
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Postby fhsen » Thu Apr 19, 2007 3:59 pm

could you dilute the solution before u add it to microscope slide so that the cells are easier to count rather than using a haemocytometer?

yes it denatures around 70 degrees, but thats when i used the methylene blue in the solution. It didnt turn completely colourless.
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Postby MadH » Thu Apr 19, 2007 6:43 pm

Hay, I have to do the same as "flyingbarbie". (the procedure behid it) Has anyone had any luck with the actual method?

Gootta love A/S Biology huh!
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