Yeast Fermentation Lab
Purpose: To determine the effect of sugar concentration on the CO2 production in a yeast solution.
Hypothesis:
Materials: List everything at your lab table and anything else you use in lab today!
Procedure: Goggles must be worn at all times in this lab!
1.
Fill the 600 ml beaker with 300 ml of water and heat to 37oC.
2.
Label 4 test tubes (with sharpie) as follows and place them in test tube rack: 0%, 1%, 5%, and 10%
(sucrose).
Create 20 ml of each of the sucrose solutions using the balance, weighing boat, and graduated cylinder
provided. Add the appropriate solution to each test tube.
3.
4.
Place 0.5 grams of yeast to each tube.
5.
Put a balloon over the mouth of each test tube.
6. Gently swirl each tube until the yeast is dissolved. Do not allow the solution to splatter up into the balloon.
7. Place the test tubes in the warm water bath in large beaker and incubate for 5 minutes before beginning to
take data.
8. Measure the depth of bubbles (mm) produced in each tube every 3 minutes up to 30 minutes. Observe and
record the appearance of the balloon by describing its overall size, as well as measuring its final
circumference at the end of 30 minutes.
Data: Create data charts for the data collected in procedure number 8.
Graph: Graph the depth of bubbles vs. time for the 4 solutions.
Calculations: Calculate the rate of reaction for each solution, by taking the highest mm of bubbles produced at
the end of the experiment, and dividing by 30 minutes. Be sure to include your units in each answer.
Conclusions:
1. What was the independent variable in the experiment? What was the dependent variable in the experiment?
2. What was the control setup of the experiment? What was the purpose of the control?
3. What are the products of this reaction? Is this reaction aerobic or anaerobic? How can you tell? How much
ATP is produced for each glucose molecule?
4. Did the yeast produce different amounts of carbon dioxide with different sucrose concentrations? Why
might this be the case?
5. What must first be done to sucrose by the yeast before this reaction can occur?
6. Was your hypothesis supported by the data? Explain.
7. Describe three sources of error that could affect the outcome of this experiment.
8. How could the procedure in this experiment be modified to improve the overall results of the lab?
9. If the purpose of this experiment is to maximize the amount of ethyl alcohol produced by the yeast, propose
a future experiment that could be done based on your conclusions from this experiment.