yeast lab fermentation 3c

Investigation: Yeast fermentation (Anaerobic Cellular Respiration)
Name: _______________________________☺
Purpose: Determine the effects of glucose concentration on yeast
fermentation by measuring the amount of gas produced.
4 small test tubes
4 large test tubes
test tube rack
yeast solution (8g/L)
distilled water
graduated cylinder (25 mL)
glucose solutions (6%, 3%, 1%)
masking tape
metric ruler
1. Label the small test tubes as control (distilled water), 1%, 3% and
2. Repeat step 1 with the large test tubes.
3. Measure out 12 mL of the 6% glucose solution and place it in the
corresponding small test tube.
4. Repeat step 3 with the 3% and 1% solutions.
5. Measure out 12 mL of distilled water and pour it in the small test
tube labeled control.
6. Top up each of the four small test tubes with yeast solution.
7. Place a large test tube over each small test tube, invert and place in
the test tube rack.
8. Label the test tube rack with your names.
9. After 24 hours, measure and record the amount of gas in each test
tube in centimeters using a ruler.
10. Smell (but do not taste!) the contents of the large test tubes.
Record your observations.
Investigation: Yeast fermentation
Name: _____________________
Due date: ______________________
Each student will submit an informal lab report for this investigation which includes:
o Class handout with Title, Purpose, Materials, Procedure
o Observations – qualitative (burning splint result) and quantitative (gas
o Answers to the Discussion questions below (using complete sentences)
Observations: include a proper data table with your quantitative observations as well as
your qualitative observations in your observations section. (5 marks)
1. a) Describe the process of anaerobic respiration in yeast. (3 marks)
b) Yeast cells can undergo aerobic respiration (using oxygen) as well as anaerobic
respiration (without the use of oxygen). How was the experiment set up to ensure that
only anaerobic respiration was happening? (1 mark)
2. a) Based on the burning splint test, what gas was most likely produced? (1 mark)
b) Many other gases have the same result for the burning splint test. To confirm the
identity of the gas, a limewater test is often done. Describe this test and the positive
result for this particular gas. (2 marks)
3. a) Identify the independent variable and the dependent variable for this investigation.
(1 mark)
b) Write a conclusion for the experiment in terms of these two variables. (1 mark)
c) After a period of time, the production of gas in the 6% glucose solution will stop
even with glucose remaining. Suggest a plausible reason for this. (1 mark)