WAH YAN COLLEGE, HONG KONG
F.5 Biology SBA Practice: Anaerobic Respiration
F.5 __ Name: _________________________________ Class No.: _________
F.5 __ Name: _________________________________ Class No.: _________
You are provided with 2 sets of the following materials and apparatus:
Glucose solution (200 cm3)
Yeast suspension (50 cm3)
Paraffin oil
Hydrogen carbonate indicator
Thermometer
Delivery tube X2
Vacuum flask with stopper (w 2 holes)
conical flask with stopper (w 2 holes)
Beaker, Bunsen burner, wire gauze, insulating mat
Design an experiment to study alcoholic fermentation of yeast
1.
What is the independent variable?
Presence of living yeast
2.
What is the dependent variable?
Occurrence of alcoholic fermentation (measured by …)
3.
How can the dependent variable be measured?
Production of heat: measure the change in temperature of the mixture with time
Production of carbon dioxide:
note the change of hydrogen carbonate indicator from red to yellow
Production of ethanol: note the production by smelling
(Explain how the dependent variable can be measured. Suggest an accurate and reliable method for the
measurement)
4.
What are the fixed variables?
Volume of yeast suspension, volume and concentration of glucose solution
5.
Suggest a control for this experiment
Repeat the experiment with boiled yeast
(State the importance of this control.)
6.
Draw a labelled experimental set-up below.
7.
How can the previous experiment be modified to compare aerobic and anaerobic respiration of yeast?
Repeat the experiment with unboiled glucose solution and remove paraffin oil
8.
9.
What measurements are to be taken?
1.
Change in temperature of the glucose solution and yeast suspension at regular time interval
2.
Time taken for the red hydrogen carbonate indicator to change from red to yellow
3.
Smell to see if alcohol is produced from the vacuum flask
What is the assumption for this experiment?
Only anaerobic respiration is carried out by the yeast cells in the set-up.
No O2 is present for the yeast cells to respire aerobically.
All carbon dioxide / heat produced is due to anaerobic respiration of the yeast cells.
(It is better to repeat the measurement. Explain.)
Discuss the limitations of the design of this investigation.)