# How to Graph Fermentation?

Name(s): Yeast Fermentation of Grapes Introduction: Yeast are single-celled organisms that are used to make wine. The process requires an anaerobic environment. Under the anaerobic conditions, yeast ferment sugars in grapes and produce alcohol and carbon dioxide (CO2). The process continues until the alcohol reaches a level that is toxic for the yeast, and therefore kills the yeast cells. The figure below shows the result of wine fermentation over a 10-day period. Use the information in the graph shown below to answer the questions that follow. Figure 1. Results from a simulation of wine fermentation (Stanley et al., 2003). The graphs show changes in grape sugar, yeast population, and percentage alcohol over a 10-day period. Questions: 1. What are the dependent variables (what is measured) in the graph above? 2. What is the independent variable (what is different) in the graph above? 3. Write a hypothesis that describes your best guess as to how the independent variable affects the dependent variables. 4. What is indicated on the Y-axis on the left? What is indicated on the Y-axis on the right? Name(s): 5. The grape sugar level starts at ____________ (include units) and ends at ____________ (include units). 6. The day at which the yeast population reaches its highest level is ___________. 7. The concentration of the yeast population on the day that the yeast population reached the highest level is ____________________. 8. At what percentage of alcohol does the yeast population begin to decline? 9. What trend do you observe in levels of ethanol and grape sugar after about 7.5 days? 10. If you would remove the alcohol as it was produced, would you predict an increase or a decrease in the amount of grape sugar at day 10? What about the yeast population? Briefly explain your answers. Source: Margaret Waterman and Ethel Stanley, BIOLOGICAL INQUIRY, A Workbook of Investigative Cases for Campbell & Reece Biology, 8th Edition