Discussion of all aspects of cellular structure, physiology and communication.
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?
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?
and whats the lowest temperature that kills all the yeast cells then?
is it around 40 degrees ish or...?
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.
I thought yesterday that a colour change could be avoided, but the plan says that you are to use the following materials
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.
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
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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