AP LAB 5 – CELLULAR RESPIRATION – 5th Period
Yeasts are single-celled organisms that belong to the fungus kingdom, a kingdom consisting of eukaryotic heterotrophs. Yeast break down glucose and
other carbohydrates to produce ATP. Yeasts are facultative anaerobes . . . they are capable of switching to alcoholic fermentation when oxygen is not
available. Both aerobic and anaerobic pathways produce CO2 as a waste product, which can then be used to determine relative rates of energy
production. In this experiment, we will compare the rate of CO2 production in set-ups using a higher concentration of sucrose, a greater
concentration of yeast cells, and a 5% lactose solution to a set-up using a 7% yeast solution and 5% sucrose solution.
Hypothesis: Predict the rate of energy production in the three test set-ups as compared to the control set-up before proceeding.
Materials:
5% sucrose
10% sucrose
5% lactose
test tubes (4)
7% yeast solution
14% yeast solution
test tube rack
ruler
small vials (4)
Procedure:
1. Label the four vials A, B, C, & D.
2. The test tubes will be set up as follows:
Test Tube
Yeast
Carbohydrate
A
10 mL of 7%
5% sucrose
B
10 mL of 7%
10% sucrose
C
10 mL of 7%
5% lactose
D
10 mL of 14%
5% sucrose
3. Use a graduated cylinder to measure 10 mLs of the 7% yeast solution for test tubes A, B, and C. Add 10 mLs of 14% yeast solution to test tube D.
4. Use a clean pipet to add the correct sugar solution to your test tube until the test tube is filled to the brim.
5. Each student must be responsible for one test tube set-up In order to do the next step correctly. The tubes must be inverted at the same time.
 Hold the test tube upright and lower the vial over it.
 Hold the test tube and vial together firmly.
 Turn them both over so the test tube stands upside down in the vial.
 Do not remove the test tube!
 Put the four vials in a safe place so they will not get knocked over!
*AP Testers - Record results in Data Table Provided*
**Non-AP Testers – Construct a Data Table to record results**
6. At 4 minute intervals, measure the height of the CO2 foam in each tube to the nearest mm. Caution: make sure you are measuring foam and not
settled yeast cells!
7. Observe and measure the CO2 foam every 4 minutes for a total of 20 minutes.
8. After the last measurement, discard the contents of the tubes and wash all materials thoroughly.
Data:
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Record CO2 measurements in Data Table 1.
Calculate the respiration rate for your table data by using the following formula: Respiration Rate (mm/min) = Δ y / Δ x
Calculate class average respiration rates using data provided.
Construct a line graph consisting of four lines to represent CO2 production in each of the four set-ups using your individual data from Table 1.
Analysis: Please answer in complete sentences!
1. What is the first step in all energy production? Provide an overview of this step, including its location in yeast cells.
2. Initially, while oxygen is still present in the tube, oxidative respiration is taking place. Describe the steps involved, including the location of each
step.
3. Explain the difference between substrate level and oxidative phosphorylation. How many ATP are gained from each in cellular respiration?
4. When oxygen is depleted, what energy pathway do the yeasts cells use? Specifically, what is the purpose of this pathway? Where does it occur?
5. For sucrose and lactose . . .
 Identify the monomers of each.
 What type of reaction joins them together? (Both names required)
 What functional groups are common to both? Provide the name and structural formula for them.
6. Identify three controlled variables in this experiment.
*Please answer the following as part of the Conclusion, if doing a formal lab write-up or as #7 for Biology AP testers.*
Provide an explanation for the respiration rate in each test set-up as compared to the control.