IB BIOLOGY
Topic 3: Chemistry of life
Title: Fermentation of Yeast
Research question: How the change in sugar substrate changes the rate of
fermentation of yeast?
Adapted from original investigation : http://www.umd.umich.edu/sep/students/mgmann/mgmann_exp.html
Background
Over 5000 years ago, the Egyptians and Babylonians were able to utilize the fermentation of wild
yeast in the form of sourdough to make raised bread (“Yeast,” 2002). Yeast is a microorganism found
in soil, plants, and air; therefore, these ancient peoples did not know what caused
their bread dough to rise. Anton Leewenhoek first observed yeast cells under his
newly discovered microscope in 1676. In 1859, Louis Pasteur found that yeast was
actually a single-celled microorganism that feeds on carbohydrates (sugar and flour)
and produces carbon dioxide gas (CO2).
There are over 600 species of yeasts, but only a few are used to make breads
and alcoholic beverages. Other yeasts can produce illness and can spoil
breads. Yeasts reproduce rapidly through fission or budding and grow especially well in
substances containing sugar. The yeasts are classified in the kingdom Fungi, phyla Ascomycota
and Basidiomycota . Yeasts of the genus Saccharomyces have been long used
commercially in the fermentation process of making alcohol and breads. Fermentation is a
process by which a living cell, such as yeast, obtains energy through the breakdown of
glucose and other simple sugars.
In this experiment, the fermentation of yeast using table sugar (sucrose), honey (fructose and
glucose), Equal® (aspartame) will be compared.
Hypothesis
If ferment yeast use different substrates then sucrose, will produce more carbon dioxide gas
“foam” than honey (fructose and glucose) which will produce more gas than the Equal
(Aspartame).
Material
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12 test tubes in test tube holder
Thermometer
Bunsen burner, Tripod, mat
200 ml Water (heated to 55oC)
6 spatulas of table sugar
6 spatulas of Equal®
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6 spatula of Honey
36 spatulas of dry active yeast
spatulas
Stop watch/timer
ruler
Method:
1. Pour 15ml of 55oC water into each of the 4 test tubes. Label each test tube 1,
2 3 or 4.
2. Add two spatula of dry yeast to each test tube.
3. Test tube #1 is a control so add nothing else to this tube.
4. Add 1 spatulas of table sugar to test tube # 2.
5. Add 1 spatulas of Equal® to test tube # 3.
6. Add 1 spatulas of Honey to test tube # 4.
7. Stir ingredients in each test tube with a clean spatula using 10 rotations each.
8. Record height of mixture in each test tube; this is the 0 minute measurement.
9. Record height of mixture in each test tube (including “foam”) in each tube
every five minutes thereafter for 30 minutes.
10. Repeat steps 1-9 two more times
Write up: Identify the IV, DV and CV then
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Results should be collected and processed
Conclusion and Evaluation completed and manipulative skills described.
Feona Crawford, Hong Kong 3/9/2016
IB BIOLOGY
Topic 3: Chemistry of life
Biology SL/H
Teacher: Feona Crawford
School: AISHK
Student Name: _____________________________
Lab Start date: ____________ Ended ___________
Total Time Spent on Lab: ___________ hours
Lab Title: __Fermentation of Yeast_________________________________________
Design
Data collection
and processing
Conclusion
and evaluation
Manipulative
Skills
Mark /6
Aspects
Not at all
Criteria
Completel
y
Partially
IB Syllabus Topic: ___Chemistry of Life____________________
Defining the problem and selecting
variables
Controlling variables
Developing a method to for collection
of data
Recording raw data
Processing raw data
Presents processed data
Concluding
Evaluates procedure(s)
Improving the investigation
Following instructions
Carries out techniques
Working safely
Achievement level
A complete is awarded 2 marks, a partial is awarded 1 mark and a not at all is
awarded 0 marks.
Feona Crawford, Hong Kong 3/9/2016
IB BIOLOGY
Feona Crawford, Hong Kong 3/9/2016
Topic 3: Chemistry of life