Comparing aerobic and anaerobic respiration with yeast

Bexley High School science teacher Janet Mulder attended Ohio Corn & Wheat-sponsored Feed the World’s summer two-day workshop. See how she used the Energy and ethanol lessons with her students:

In my Honors Biology class, we spend a chapter on how organisms obtain energy, through cellular respiration and photosynthesis. This connects with State Standard/Learning Objective B.C.2: Cellular processes: Identify the cellular sites of and follow through the major pathways of anaerobic and aerobic respiration; compare reactants and products for each process, and account for how aerobic respiration produces more ATP per monosaccharide.

We have done a cell respiration lab with yeast going through aerobic cell respiration with different sugars. In the past we have talked about how yeast can go through aerobic and anaerobic respiration, but we never did a lab with anaerobic respiration.

While attending the Feed the World workshop, we went through the Corn Fermentation in a Bag lab. This seemed like the perfect lab to add in order to compare aerobic and anaerobic respiration with yeast. I modified the lab in order to fit within the timeframe of our unit, and had students do this after the aerobic respiration lab.

Fermentation is part of the process of creating ethanol, breaking down the starch in corn into simple sugars (glucose), feeding these sugars to yeast (fermentation), and then recovering the main product (ethanol) and byproducts (animal feed and carbon dioxide).  Ethanol from corn is a renewable resource, and ethanol-fueled vehicles produce lower carbon dioxide emissions and similar or lower levels of nitrogen oxide emissions.

This activity was a great way to help students make comparisons and connections, as well as to take some ownership in selecting their sugars/corn product and justifying their choice. This brought out the competitive streak in some as they wanted to have the most respiration! For most classes, the outcomes were what I would have expected, although in general the bags did not expand too much, only a few millimeters in difference. We talked about lengthening the experiment to allow for more respiration. In addition to this, a student made the observation that our room is cold and the lab tables are cold. The student wondered if this could have hindered our results because we had talked about yeast preferring a warmer environment. Students then brainstormed ways we could warm the table, without cooking the yeast, in order to potentially have better results.

The lab provided valuable comparisons between aerobic and anaerobic respiration, which we continued to reference throughout the chapter. The more hands-on activities we can use, the better students’ experience in science becomes. This was a great addition to our current labs, and I look forward to continuing to use this lab and others from the Feed the World Curriculum.