Photosynthesis and Cellular Respiration
Background: Plants make sugar, storing the energy of the sun into chemical energy, by the process of photosynthesis. When they require energy, they can tap the stored energy in sugar by a process called cellular respiration.
The process of photosynthesis involves the use of light energy to convert carbon dioxide and water into sugar and oxygen.
PHOTOSYNTHESIS 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
Cellular respiration refers to the process of converting the chemical energy of organic molecules into a form immediately usable by organisms. Glucose may be broken down if oxygen is available by the following equation:
CELLULAR RESPIRATION C6H12O6 + 6O2 → 6H2O + 6CO2 + energy
Objectives: In this experiment, you will
1. Use a carbon dioxide sensor to measure the amount of carbon dioxide consumed or produced by a plant during cellular respiration and photosynthesis.
2. Determine the rate of respiration and photosynthesis of a plant.
3. Determine if the color of light impacts the rate of photosynthesis in a plant.
Materials:
Labquest Carbon Dioxide Sensor Plant leaves (spinach or parsley)
Lamp Aluminum Foil Heat sink (beaker filled with water)
Biochamber
Procedure:
No Light
1. Check that the CO2 sensor is set to LOW (0-10,000 ppm). Connect the CO2 sensor to Channel 1 of the Labquest.
2. Obtain 2 spinach leaves. Blot them dry if damp.
3. Place the leaves into the Biochamber. Wrap the chamber in aluminum foil so that no light reaches the leaves.
4. Place the CO2 sensor into the neck of the respiration chamber as shown below. Wait three minutes before proceeding to step 5.
5. Record the CO2 level every minute for 10 minutes. Copy your data into the provided data table.
Photosynthesis with Ambient Light
6. Remove the aluminum foil from around the chamber.
7. Let the leaves acclimate to the light for 3 minutes.
8. After the three minutes, begin data collection. Record the CO2 level every minute for 10 minutes. Copy your data into the provided data table.
Photosynthesis with White Light
9. Place the chamber in front of the lamp with a heat sink between the lamp and the chamber.
10. The lamp should be on for 3 minutes prior to beginning data collection.
11. After the three minutes begin data collection. Record the CO2 level every minute for 10 minutes. Copy your data into the provided data table.
Data Analysis
1. Graph the results of your three experiments.
2. Determine the rate of photosynthesis on the 3 experiments (CO2 consumed / min).
3. Write the rates below the graph.
Lab Questions: Write the answers to your questions in your lab notebook.
1. Would the number of leaves affect your data? Why or why not?
2. Do you have evidence that photosynthesis occurred in the spinach leaves? Explain.
3. Do you have evidence that cellular respiration occurred in the spinach leaves? Explain.
4. List 5 factors that might influence the rate of carbon dioxide consumption in the leaves.
Table 1: Carbon Dioxide Output and Consumption in Spinach Leaves
Treatment / Carbon Dioxide (ppm)0 min / 1 min / 2 min / 3 min / 4 min / 5 min / 6 min / 7 min / 8 min / 9 min / 10 min
No Light
Ambient Light
White Light
Table 1: Carbon Dioxide Output and Consumption in Spinach Leaves
Treatment / Carbon Dioxide (ppm)0 min / 1 min / 2 min / 3 min / 4 min / 5 min / 6 min / 7 min / 8 min / 9 min / 10 min
No Light
Ambient Light
White Light
Table 1: Carbon Dioxide Output and Consumption in Spinach Leaves
Treatment / Carbon Dioxide (ppm)0 min / 1 min / 2 min / 3 min / 4 min / 5 min / 6 min / 7 min / 8 min / 9 min / 10 min
No Light
Ambient Light
White Light
Table 1: Carbon Dioxide Output and Consumption in Spinach Leaves
Treatment / Carbon Dioxide (ppm)0 min / 1 min / 2 min / 3 min / 4 min / 5 min / 6 min / 7 min / 8 min / 9 min / 10 min
No Light
Ambient Light
White Light
Modified from Investigating Biology through Inquiry, Vernier