Cellular Respiration in Yeast
In the lab, Cellular Respiration in Yeast, students learn about the basics of metabolism and then design and carry out experiments to test how sugar concentration and other variables influence the rate of anaerobic respiration in yeast. In an optional extension activity students can use their yeast mixture to make a small roll of bread.
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We invite comments on this Hands-On Activity and the accompanying Teacher Preparation Notes, including suggestions for other teachers who are planning to use the activity, useful preparatory or follow-up activities, additional resources or any questions you have related to the activity, or a brief description of any problem you might have encountered. If you have a relevant Word document you would like to have posted on this comments page, such as a version of the protocol you have used in your classroom, or if you would prefer to send your comments or questions in a private message, please write Ingrid Waldron at iwaldron@sas.upenn.edu.
See also a complete list of activities:
Hands-on Activities for Teaching Biology to High School and Middle School Students
Respiration Lab
We did this lab on a Friday and left it for the weekend.
We got foaming and some gas produced after 20 minutes. By the end of the day the 10% and 5% solutions had produced enough gas to measure but the students never saw it.
By Monday morning the gas was all gone due to the fact that the building is not heated on the weekends.
I suggest doing the lab on a weekday and looking at results after 24 hours.
We also added BTB solution to each one for a color change which showed the production of carbon dioxide gas.
getting results within one class.
It should be possible to complete Part I of this activity in one class period. To ensure that your students can observe results at 10 and 20 minutes, be sure to use rapid rise or fast acting yeast that is not near or past its expiration date and water that is between 80°F and 115°F.
Yeast & Celluar Resp.
Just a comment about the yeast used. I used baker's yeast which claims to be Saccharomyces cerevisiae.
This yeast did nothing after 10 minutes, 20 minutes, after 30 min there was some action. This is not useful for a 90 minute period as there is no visible buildup of CO2 and 'measure the bubbles' means nothing if there aren't any, or they are not in the same area (after overnight they were distributed throughout the tube).
Just wondering what I did wrong? I used water heated to 38degC and the 0%,1%,5%,10% solutions. However nothing happened....is there something wrong with my yeast? Does it go off? Should I not be using baker's yeast?
As an addendum, I wanted to view the comments for this activity to see if someone had already answered this question but only this form came up, no prior comments area. Maybe it would be easier if I could just see the comments and then I might be able to work this out without posting!
Thanks for the lab, I think it's good but I couldn't get it working.....any advice?
Jason
advice to ensure that your yeast will grow
We are sorry you had problems getting the yeast respiration lab to work in your classroom. Simply mixing yeast, sugar, and warm water (80-115 F) into a homogeneous solution will cause the yeast to start respiring. If yeast do not respire (release gas and make bubbles) when mixed with warm water and sugar there is either something wrong with the 1) yeast or 2) water.
Problems with the yeast could be that it is too old or was exposed to extreme heat or cold. Problems with water could be that it was too cold (below 80 F) or too hot (above 120 F) or has too many impurities (this would be very rare and would probably only be the reason if you used non-potable water). If you start with water that is too hot and it cools to warm water, the yeast may still have been killed while the water was too hot.
The speed at which the yeast respire will depend on how fast the warm water cools off in your classroom (how warm or cold your classroom is), however as your yeast mixtures didn't produce any bubbles I suspect that was something off with your yeast or water.
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