[EXPT] Astudy on respiratory substances

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Tolland
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[EXPT] Astudy on respiratory substances

Post by Tolland » Wed Apr 18, 2007 10:16 am

In group discussion, Paul pointed out that respiratory substance is one of the main factors affecting the rate of respiration. His classmates did not support his suggestion. They tried to perform investigations instead of just debating for the truth.

You are provided with the following materials and apparatus: glucose solutions of two different concentration, yeast suspension, starch solution and sucrose solution, rubber tubings, Mohr's clips, water bath, small pipettes.


I am given the above instruction to design a experiment, but I am a bit confused to think the beginning of the experiment.
How can I perform the experiment?
What control variable I need to set up?
Do I need to make any assumptions or precautions for the experiment?

:oops: :oops: :oops:

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mith
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Post by mith » Wed Apr 18, 2007 2:02 pm

It would be helpful to know the definition of "respiratory substance"
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Tolland
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Post by Tolland » Wed Apr 18, 2007 2:31 pm

I know it. It is the substance for respiration to provide energy for the activity of yeast.
But the difficult part is to follow the experiment to do the study,, sosad,,,,,,

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kotoreru
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Post by kotoreru » Wed Apr 18, 2007 2:39 pm

I won't do this work for you, but I'll give you hints:

Several batches of yeast. Repeats?

Each should have a different 'respiratory substance'. Will you vary the concentrations?

What variables will you keep constant?

Remember, in Science we try to keep most things constant and change only the thing we are interested in (massive generalisation, but important to understand). Keep things simple. This is not as hard as it seems.

If you are really stuck, ask back here.
"What are humans if they don't learn at University? Animals, yes."

^^One of my ex-girlfriends said that. I stress the ex part.

Tolland
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Post by Tolland » Wed Apr 18, 2007 4:27 pm

yes
i have also thought about it and now i get the most of the concept for doing it
but i m not sure it is required to vary concentration as it is difficult to control large amount at the same time and i think 2 concentration given is enough to compare the rate of respiration~

i suppose only 4 pipette can be prepared:
conc. glucose-yeast
diluted glucose-yeast
sucrose-yeast
starch yeast
but do i need to prepare the water-yeast for control expt?any advice?

for the variables, i am not sure if i specify correctly~
independent: volume of yeast and respiratory substance like glucose,etc
dependent: volume of co2, time interval of water bath
control: temperature of water bath
could you tell me if i miss other variable i have not mentioned yet?

at last, i am a bit confused of the pecaution and assumption of this expt?
could u pls give me some hints?thx~~~
:D

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Post by kotoreru » Thu Apr 19, 2007 10:40 am

Alright, there's a start. I'm not sure at which level you are studying this at, though I'm guessing probably GCSE? (Sorry I really dont know any equivalents in other countries).

If that's the case then probably half of what I'm giving you is 'too much'.

Ok so you have figured out 4 pipettes. Is that a fair test? 2 concentrations of glucose: which one will you compare to the sucrose and starch? What concentrations are they at? Perhaps you could do two concentrations of each substrate?

So you are measuring the C02. OK. Time interval in the water bath...is that going to be constant? Or could you compare temperature of yeast to volume of CO2 released in a given time? When will you stop measuring?

Not sure what you mean by pecaution and assumptions...unless you are given assumptions then why not make them for yourself? Perhaps something like, "the volume of C02 released in 5 minutes is dependant on the concentration and type of substrate given". No?

Hope that helps, but I'm trying not to do your work for you...

Again, ask back if you get stuck, happy to help.
"What are humans if they don't learn at University? Animals, yes."

^^One of my ex-girlfriends said that. I stress the ex part.

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