Science Buddies: "Ask an Expert"

Hello,

I have completed the experiment that tests yeast metabolism under aerobic and anaerobic conditions. Basically I made a yeast/sugar solution in warm water (keeping all those variables constant), aerated it for 5 minutes, and then colleted the CO2 it produced in an inverted graduated cylinder. I repeated this for a total of 3 trials and then repeated again without aerating it.

I calculated the average amount of CO2 produced and everything, but I am just a little bit confused as to what the amount of CO2 produced has to do with the yeast metabolism. Is it that the more CO2 produced, the faster the yeast metabolized? I am at the "Results Interpreted" part of my report.

Thank you!
Caroline

Hi Caroline,

You are almost right. When yeast digests sugar it breaks down the molecules for energy just like we do and one of the by-products of this chemical reaction is CO2. If there is oxygen present then the yeast cells use it for respiration as we do, producing CO2 in the process. But if oxygen is absent, the yeast can perform anaerobic fermentation, a metabolic process that breaks down the sugar but also produces CO2 and ethanol.

In both aerobic and anaerobic situations, yeast cells produce CO2 as a breakdown product of the sugar and that is what you are collecting and measuring in this experiment. What was your result? Was there more CO2 gas given off in one condition compared to the other or were they the same? Explain your results.

Here are some references about yeast metabolism for more information:

http://www.diffen.com/difference/Aerobi ... espiration
http://www.bbc.co.uk/education/guides/z ... revision/2
https://en.wikipedia.org/wiki/Yeast

If you need more help with this, let us know.

Good luck!

Sybee