Cellular respiration biology lab discussion

[judi6070]

I need help writing a discussion for the biology lab report that I'm doing. If anyone could help in explaining the results it would be much appriciated. Here's the experiment...

We had 6 flasks each containing yeast, sugar and water. 2 of the six we added 5ml of 1.0 M HCl and into two others 5ml of 1.0 M NaOH was added. This created 2 acidic environments, 2 neutral environments and 2 basic environments. One of each type of environment was set to grow in anaerobic conditions and the other in aerobic conditions. The intial pH of the solutions were: Acidic=2, Neutral=7, Basic=10.

Our experiement was meant to see if the yeast growing in either an aerobic or anaerobic condition would effect the pH of the solution. The results were that all six flasks had an ending pH of 3.

Are these results the ones we should have got, or did we screw up the experiment somewhere along the way?? It seems to me that these shouldn't be the results, but if anyone knows differently please let me know. Any insight would be helpful!

 

[pattylou]

Those are not the results that you should have gotten. *

How did you measure pH (both starting and final)? Did you have standards to make sure your pH meter (or pH strips) were accurate?

How long did you let the cultures grow, were they shaking (particularly the aerobic ones) and is it possible that they were seriously contaminated? Was the oxygen in the corked flask removed in some manner at the start of the incubation?

Have you checked with other lab groups to see what results they got?

Did the growth *appear* to be roughly the same in all flasks?

-patty

*I have not done this particular lab, but I believe I know what result/answer was expected in theory.

 

[judi6070]

The pH was measured using Universal Indicator Solution (30 drops in each flask). The cultures were growing for approximately a week and they were all shaken on a semi-daily basis. the oxygen in the anaerobic ones was not sucked out at the begginning, but were corked with very little air in the flask. The growth did appear to be very simmilar in each flask. Could you share the theoretical results are supposed to be? Thanks