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effect of temperature on the survival of yeast cells

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Alternative to all mentioned before

Postby Gomez » Wed May 02, 2007 4:34 pm

Has noone considered that you can collect CO2 instead of looking for the colour change? Apologies if someone already has.

When I went for preliminary sess today, I was told I could use anything in the lab, and obviously not to use all. How about this then???

Use a side arm flask with a bung and a gas syringe, heat the yeast suspn in a tube (in a water bath) to whatever temp you want then pour it into the side-arm flask, add the sugar and bung the flask, and check the volume of CO2 created after 5-10 mins.

Can anyone see if I've missed something obvious with this?
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Postby rooo » Wed May 02, 2007 5:13 pm

Well, the question aint saying anything abut collecting the CO2. I think you gotta do the color change... :roll:
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Postby bricktop » Wed May 02, 2007 6:40 pm

anyone know the method for this investigation please?

just confused about the order in which you put them in and the the time intervals

thanks
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help!

Postby emmaaa_ » Wed May 02, 2007 7:55 pm

how confusing is this yeast cell thing?

i didn't use a colorimeter or anything in my preliminary work!

i had 5 boiling tubes and
a water bath heated by a bunsen burner

put yeast suspension + sucrose in the tubes and heated them individually to different temps (i chose 30, 40, 50, 60 + 70)

and then after heatin them for 2 mins

i put a drop of the yeast/sucrose mixture onto a microscope slide + added a drop of methylene blue

and then observed it with a microscope


is this right?

or is it not detailed enough?

i didn't have time to finish all the experiment tho

but results are needed are they?


help :]

and whats the lowest temperature that kills all the yeast cells then?

is it around 40 degrees ish or...?

xo
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Postby bricktop » Wed May 02, 2007 8:26 pm

think the lowest temp is about 50-55 degrees that kills them.

i'm well confused about the method...

what are the numbered steps?

what do you do first?
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Re: Im so confused...help

Postby Gatz » Wed May 02, 2007 8:29 pm

Star12 wrote:Right i did a preliminary for this experiment and it went completely wrong...i ranged my temperatures between 40-70 degrees C and none of them went blue they all turned clear...can any1 explain this?


Yeast cells are only active within a certain temperature range. This tends to be within 30-38 (optimum temps) after around 40 degrees they denature and lose their function. (they die and so no metabolic activity takes place). Therefore the indicator will remain clear as all the yeast cells are dead.
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Re: Im so confused...help

Postby Ulbrid » Wed May 02, 2007 10:29 pm

Gatz wrote:Therefore the indicator will remain clear as all the yeast cells are dead.


It will stay blue; it's colourless when there is enzyme activity.
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Need to do colour change

Postby Gomez » Thu May 03, 2007 2:49 pm

I thought yesterday that a colour change could be avoided, but the plan says that you are to use the following materials

10% yeast
10% sucrose / glucose
1% methylene blue

I found I couldn't readilly tell the difference between alive and dead as its hard to see on a light microscope. But for those who're comfortable with that try diluting the yeast/sugar/indicator solution with 20 parts distilled water to 1 part solution. This might also help with the colourimetry.
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Postby mojo » Thu May 03, 2007 4:30 pm

I did my prelim for this experiment today and something about it really confused me!! I first used Glucose as the sugar, and the Yeast respired a bit but REALLY REALLY slowly, so within the time there wasn't really a colour change of the methylene blue, even though I performed it at optimum temperature for the respiration of yeast. Then I tried it with the sucrose and it worked perfectly. The same thing happened to everyone else in my class.

I had thought that you should use glucose, because its a monosaccharide, whereas sucrose is a disaccharide and would have to be broken down into glucose and fructose for the yeast to be able to use it's energy!! Can anyone answer why this happened? Either all of my sources are wrong, or the technicians mixed up the labels on the beakers :P
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Postby emmaaa_ » Thu May 03, 2007 5:19 pm

can someone help?

i need to know what happens to the yeast cells at a range of temperatures?



my teacher said i can use the internet to find out what happens to yeast and blah blah and use this to help write the plan


help? :]
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Postby nano » Thu May 03, 2007 5:30 pm

heey
i just popped onto this forum
and its really helped me
so i thought id say thanks
and was just woundering, what everyones putting down for their referencing?
because i couldnt say this forum could I? :S
thanks for any help

xx
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Postby Ulbrid » Thu May 03, 2007 6:53 pm

emmaaa_ wrote:can someone help?

i need to know what happens to the yeast cells at a range of temperatures?



my teacher said i can use the internet to find out what happens to yeast and blah blah and use this to help write the plan


help? :]


I don't really understand what you're asking...
Metabolic activity is low at low temperatures (i.e. below 30 degrees Celsius).
Metabolic activity is highest at optimum temperatures (i.e. 32 - 37 degrees Celsius- that's just a rough estimate, by the way).
Metabolic activity is lowest at high temperatures (i.e. above 40 degrees Celsius) because the enzymes in the yeast cells begin to denature so is cannot respire effectively.
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