Effect of glucose conc on rate anaerobic respiration - yeast

[weeman10789]

Hi! I need assistance with some A2 coursework i am currently doing, which is entitled 'Investigating the effect of glucose concentration on the rate of anaerobic respiration', any help would be great!

[Happydadtoo]

You need to do some preliminary expts to get a suitable range - I'd suggest 0.1% to 25%.
You need a suitable temperature - one of the best is room temp (but that is measured and recorded)!
You need a suitable suspension of yeast - try 2 or 5%, BUT you need to keep agitating to ensure that each sample is the same. That's the biggest source of error and is the main explanation for any anomalous results you get.
Place 1cm3 yeast + 9cm3 of glucose in a 10cm3 syringe and place it pointing down in a stand and clamp. Under it, put a beaker on a top-pan balance.
Now, as the yeast ferments, it will produce CO2, which will force the mixture out of the syringe.
You can now either count drops (Ok-ish) or record the mass (much better) - with a datalogger/pc you can set it up and allow the whole thing to run itself.

Now repeat x3 and average results

Then repeat (x3 again) with each of the other concentrations of glucose. You need at least 5 concs - 7 is better. prepare stock solutions of each (ie 50cm3, all diluted from one 'master' solution)

Plot graphs of average rate of fermentation v conc of glucose.

Stats? - Try Mann-Whitney or Spearman's rank, when your null hypothesis is that conc has no effect.

Key part of write-up? Include explanations as to WHY each step was done and FULL details (eg was beaker glass or plastic and what size?) at each stage. Then remember to give BIOLOGICAL reasons why to expect XXXX for your results AND the science behind that.
Don't forget a hypothesis. You need to FULLY justify each and every step of your procedure and explain why you are/are not taking precautions to ensure accuracy (eg temp will be measured throughout and would be hard to stabilise more accurately). One way round that is to wrap the syringe in damp paper towel, thus providing SOME cooling, since vey high rates will tend to genrate heat and affect the results (or leave that out and then use it as a source of error later)
Hopetaht helps!
HD2