Purpose: To design an apparatus appropriate for studying alcoholic fermentation by yeast.
Materials and Methods:
- Working in groups of 2 or 3 and using their own materials, students will design and build an apparatus similar to the one in the diagram below that is capable of supporting alcoholic fermentation. The only teacher supplied materials will be the yeast and sugar solution, limewater, and some lab equipment.
- Both flasks (or other suitable containers) should be stable in an upright position.
- One flask should be designed to hold around 300 mL of solution with a space above it for the tubing (which will not be immersed). The other flask should be designed to hold around 25 mL of limewater with the tubing immersed.
- Student names should be clearly labelled on the apparatus.
- Students will be evaluated on their design, the successful production of alcohol, and answers to a number of questions related to the experiment.
- Draw a large, well-organized, labelled diagram to illustrate your apparatus and the materials you used.
- Draw a large flowchart illustrating the chemical reactions of alcoholic fermentation.
- Did your apparatus successfully produce alcohol?
- Describe the tests used to detect the presence of alcohol and the proper observations.
- In addition to alcohol, what other product was made? Describe the test used to detect this substance.
- Would yeast ferment better with maltose or lactose as an energy supply? Explain in terms of cellular respiration.
- Why would the addition of starch and amylase lead to increased alcohol production? Explain in terms of cellular respiration.
- Fermentation can also produce vinegar. Research this biochemical process.
(a) Identify the organism responsible for producing vinegar from ethanol.
(b) Is vinegar production aerobic or anaerobic? Explain.
(c) Describe how the relationship between the yeast and this organism is a form of symbiosis.
- Discuss modifications to your design and/or scientific method that would improve alcohol production.
- Discuss modifications to your design and/or scientific method that would allow alcohol production followed by vinegar production.