Respiration of Sugars by Yeast

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Respiration of Sugars by Yeast

What is the effect of the type of sugar on the amount of carbon dioxide released by Yeast during aerobic respiration?

If the type of sugar is changed, the amount of carbon dioxide created will then increase because sugar is needed to for respiration so occur. If Fructose is added to the Yeast it will then respire the most Co2 because fructose is the largest sugar, its like using a hundred dollar bill instead of single dollars.

A. Background Information (:
Yeast are able to metabolize some foods, but not others. In order for an organism to make use of a potential source of food, it must be capable of transporting the food into its cells. It must also have the proper enzymes capable of breaking the food’s chemical bonds in a useful way. Sugars are vital to all living organisms. Yeast are capable of using some, but not all sugars as a food source. Yeast can metabolize sugar in two ways, aerobically, with the aid of oxygen, or anaerobically, without oxygen.

Figure 1

In this lab, you will try to determine whether yeast are capable of metabolizing a variety of sugars. When yeast respire aerobically, oxygen gas is consumed and carbon dioxide, CO2, is produced. You will use a CO2 Gas Sensor to monitor the production of carbon dioxide as yeast respire using different sugars. The four sugars that will be tested are glucose (blood sugar), sucrose (table sugar), fructose (fruit sugar), and lactose (milk sugar). B. VARIABLES

manipulated: Type of Sugar
Responding: Amount of CO2
Controlled variables: Test tubes, Same amount of sugar, Similar Yeast cells, Ambient temperature C. MATERIALS LabPro interface
600 mL beaker (for water bath)

Palm handheld
Beral pipets

Data Pro program
hot and cold water

Vernier CO2 Gas Sensor

250 mL respiration chamber
four 10 X 100 mm test tubes

5% glucose, sucrose, Water, and fructose sugar solution
yeast suspension

Graphical Analysis or Logger Pro (optional)


1. Prepare a water bath for the yeast. A water bath is simply a large beaker of water at a certain temperature. This ensures that the yeast will remain at a constant and controlled temperature. To prepare the water bath, obtain some warm and cool water from your teacher. Combine the warm and cool water into the 600 mL beaker until it reaches 38 – 40°C. The beaker should be filled with about 300 – 400 mL of water. Leave the thermometer in the water bath during the course of the experiment to monitor the temperature of the water bath.

2. Obtain four test tubes and label them G, S, F, and L.

3. Obtain the four sugar solutions: glucose, sucrose, fructose, and lactose.

Place 2 mL of the glucose solution in test tube G.
Place 2 mL of the sucrose solution in test tube S.
Place 2 mL of the fructose solution in test tube F.
Place 2 mL of the lactose solution in test tube L.

4. Obtain the yeast suspension. Gently swirl the yeast suspension to mix the yeast that settles to the bottom. Put 2 mL of yeast into each of the four test tubes. Gently swirl each test tube to mix the yeast into the sugar solution.

5. Set the four test tubes into the water bath.

6. Incubate the test tubes for 10 minutes in the water bath. Keep the temperature of the water bath constant. If you need to add more hot or cold water, first remove as much water as you will add, or the beaker may overflow. Use a Beral pipet to remove excess water. While the test tubes are incubating, proceed to Step 7.

7. Plug the CO2 Gas Sensor into Channel 1 of the LabPro interface. Connect the handheld to the LabPro using the interface cable. Firmly press in the cable ends.

8. Press the power button on the handheld to turn it on. To start Data Pro, tap the Data Pro icon on the Applications screen. Choose New from the Data Pro menu or tap to reset the program....
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