Alcoholic Fermentation in Yeast - Serendip

Experiment I - Effects of Sucrose Concentration on the Rate of AlcoholicFermentation in Yeast1. Humans use yeast every day to make bread, wine and beer. What is yeast?If you want to make your own bread, you can buy yeast in the grocery store. This yeastconsists of little brown grains. The little brown grains of yeast may not seem to be alive, but ifyou put them in water with sugar, the yeast will take up the sugar and use the energy stored inthe sugar molecules to make ATP and carry out the processes of life.2. What is sucrose?Yeast can convert sucrose into glucose and use the glucose to provide the energy to makeATP.3. In your experiment, you will grow yeast in a test tube filled with water and sealed with aballoon. Do you think these growth conditions are aerobic or anaerobic?Under anaerobic conditions, yeast carries out glycolysis to produce ATP, followed by alcoholicfermentation which produces _________________ and ____________________.To measure the rate of alcoholic fermentation in yeast, you can measure the amount of CO 2 gasthe yeast produces. CO 2 production can be measured by measuring the depth of the layer ofbubbles trapped in foam on top of the yeast solution and also by observing the balloons, whichget bigger as they catch the CO 2 produced by the yeast.4. To test whether the concentration of sucrose affects the rate of alcoholic fermentation inyeast, you will measure the rate of CO 2 production for 4 different concentrations of sucrose.Complete the table to predict how much CO 2 production you expect in each case.Sucrose ConcentrationPredicted Amount of CO 2 Production(e.g. a little, none, the most,less than..., more than..., the same as...)0% (plain water)1% sucrose5% sucrose10% sucrose4. What will be the independent variable in your experiment?What will be the dependent variable in your experiment?5. What will be the control treatment in your experiment?What is the purpose of this control treatment?2