Featured in PASCO’s Advanced Biology through Inquiry Teacher Guide
This manual features 22 challenging, standards-based, inquiry lab activities for AP, IB, and honors programs.
Students use an ethanol sensor to determine the ability of yeast to use different types of carbohydrates—sucrose and starch—for fermentation.
Students determine the ability of yeast to use different types of carbohydrates—sucrose and starch—for fermentation. Yeast are facultative aerobes, carrying out both aerobic respiration and fermentation, depending on whether oxygen is readily available. When yeast ferment sugar, they produce ethanol and carbon dioxide and obtain ATP from glycolysis.
C6H12 O6 + 6O2 --> 2CO2 + 2C2H5OH
Since carbon dioxide is a product of both aerobic respiration and fermentation, this lab makes use of an ethanol sensor to measure a product formed only during fermentation. (Both processes can occur simultaneously, so measuring carbon dioxide concentration is not a direct measurement of the rate of fermentation.)
Best results are obtained using active dry yeast purchased in packets, as opposed to a jar of active yeast. Be sure the expiration date for the yeast has not passed. The ethanol sensor probe contains a heating element. It can take up to 10 minutes for the sensor’s temperature to stabilize. The “warm-up” period should occur prior to calibration. (Refer to the product manual for calibration procedures.)
This experiment may require software and an interface for data collection.