Effect of Different Isomers of Sugar on Yeast Respiration
Author(s): Tom Schuster, Rosalie Van Zyl, & Harold Coller
Longitudinal Study
SED 695B; Fall 2005

Research Question:

Students are often confused by the term isomer. Eventually, they memorize a definition and know that isomers share atomic composition, but vary in their structures. What are the consequences for organisms? Can organisms use any molecule for energy as long as they have the same chemical formulas? Or does the structure of each molecule affect the usefulness of a molecule? In this investigation, it is determined that not all sugar is the same. Only certain configurations of sugar molecules can be used by yeast.


Three Monomers Shown Below--Three Dimers Shown Above

sugars

A Possible Setup
setup

Standards addressed:

Biology/Life Sciences
Cell Biology
1. The fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism’s cells. As a basis for understanding this concept:
b. Students know enzymes are proteins that catalyze biochemical reactions without altering the reaction equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of the surroundings.
g. Students know the role of the mitochondria in making stored chemical-bond energy available to cells by completing the breakdown of glucose to carbon
dioxide.
h. Students know most macromolecules (polysaccharides, nucleic acids, proteins,
lipids) in cells and organisms are synthesized from a small collection of simple
precursors.

Investigation and Experimentation
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform
investigations. Students will:
d. Formulate explanations by using logic and evidence.
Independent variable
Dependent variables
Controls
Series
Time (minutes)

Carbon Dioxide Production
Sugar concentration
Yeast
Water
Temperature
Monosaccharides:
Dextrose (Glucose)
Levulose (Fructose)
Galactose
Disaccharides:
Sucrose
Maltose
Lactose

source bottles

Procedures:

  1. Fill the six eudiometers with colored tap water (colored water is easier to read). Invert each in a 600mL or larger beaker on a ring stand.
  2. Create 10% solutions of each of the six sugars. (add 10.0g sugar to 90.0mL purified water) each in a 250mL Erlenmeyer flask. Label each flask.
  3. Assemble #5 stoppers with glass and rubber tubing.
  4. Measure six 1.0g portions of yeast. Place each portion in a different flask.
  5. Install the stopper apparatus into each test tube. Insert the unattached end of each rubber tube into the corresponding inverted eudiometer.
  6. Start the clock. Record the volume of carbon dioxide produced at 5 or 10 minute increments until no more gas can be measured.
  7. Graph data as indicated in the example below.

Materials:

Labware:

  • Electronic Balance
  • Weighing Dishes or Paper
  • 6 x 600mL beakers or larger
  • ring stands with clamps
  • 100mL Graduated Cylinder
  • 6 x 250mL Erlenmeyer Flasks
  • 6 x single-hole #5 Rubber Stoppers
  • 6 x 4" Glass Tubing
  • 6 x 10" Lengths Rubber Tubing
  • 6 x 100mL Eudiometers
  • 540mL Purified Water
  • Tap Water (for displacement)
  • Food Coloring (optional)
  • Clock

Consumables:

  • 2 x 7g Packages Dry Yeast
  • 10g Dextrose (Glucose)
  • 10g Levulose (Fructose)
  • 10g Galactose
  • 10g Sucrose
  • 10g Maltose
  • 10g Lactose
 
 
Saccharide
Formula
 Structure
Dextrose
(carbon ring)
mono
D-Fructose
(linear)
mono
Galactose
(carbon ring)
mono
Sucrose
(glucose + fructose)
dimer
Maltose
(glucose + glucose)
dimer
Lactose
(glucose + galactose)
dimer

Sugars are simple carbohydrates. Also called saccharides, the come in two forms: monosaccharides and disaccharides. Monosaccharides have the chemical formula
mono
and Disaccharides have the chemical formula
dimer.
However, many different configurations exist for each of the two kinds. These different configuration of atoms are called isomers. Isomers of sugars are important to life because organisms have evolved various enzymes to access the energy in each form. Some organisms are therefore better at getting at some forms of sugar than other forms because of the enzymes that they can use.

 
 
data
 This table shows the data collected every 5 minutes until no more gas could be collected.
 
 
graph
Clearly, maltose is the best for yeast metabolism. Remember, yeast is made of two glucose molecules. Glucose (aka dextrose) is a close second. Fructose is in third place. Interestingly, sucrose, made of glucose and fructose, does not perform well. Perhaps yeast do not have an enzyme to access sucrose's energy. Fructose, galactose, and lactose produced very little, if any cellular respiration in yeast.
monomersdimers

It is interesting to note that, not only do these sugars look different, but they also have distinct odors.

 
yeast
 Each gram of yeast contains about 1 billion cells. That's 1,000,000,000 cells!
 

References & Links:

General info on yeast
Fleischmann's Yest Home Site
Cellular Respiration and Yeast