Esciencelabs Respiration

Respiration Procedures

Procedure 1:

1. Mix ¼ tsp of yeast into 175 mL of warm (40-43 C) water in a 250 mL beaker. Stir until dissolved.

2. Label the big and small test tubes 1-5.

3. In a 250 mL beaker, mix the 1 gram packet of Equal with 100 mL of water. In another 250 mL, mix the 1 gram packet of Splenda with 100 mL of water. In another 250 mL beaker, mix half of the 4 gram packet of sugar with 200 mL of water.

4. Fill the smaller test tubes with 15 mL solution as follows:

• Tube 1: 1% glucose solution

• Tube 2: 1% sucrose solution

• Tube 3: 1% Equal solution

• Tube 4: 1% Splenda solution

• Tube 5: 1% sugar solution

5. Then, fill each tube to the top with the yeast solution.

6. Slide the corresponding larger tube over the small tube and invert it as practiced. This will mix the yeast and sugar solutions.

7. Place respirometers in the test tube rack, and measure the initial air space in the rounded bottom of the internal tube. Record these values in Table 1.

8. Allow the test tubes to sit in a warm place (~37 C) for one hour.

9. At the end of the respiration period, measure the air space in the internal tubes, and record in Table 1.

Table 1: Gas production

Tube

Initial gas height (mm)

Final gas height (mm)

Net change

1

7 mm

8.5 mm

1.5 mm

2

7 mm

9 mm

2 mm

3

5 mm

5 mm

0 mm

4

4 mm

4 mm

0 mm

5

5 mm

6 mm

1 mm

Questions

1. Hypothesize why some substances were not metabolized, while others were. Research the chemical formula of Equal and Splenda and explain how it would affect respiration.

2. If you have evidence of respiration, Identify the gas that was produced. Suggest two methods for positively identifying this gas.

3. How do the results of this experiment relate to the role yeast plays in baking?

4. What would you expect to see if the yeasts’ metabolism was slowed down? How could this be done?

5. Indicate sources of error and suggest improvement.

Procedure 2:

1. Fill two beakers with...