IB Photosynthesis Vernier Exploration
Plants make sugar, storing the energy of the sun into chemical energy, by the process of photosynthesis. When they require energy, they can use the stored energy in the 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, oxygen, and other organic compounds. This process is often summarized by the following reaction:
6H2O + 6CO2 + 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 oxidized completely if sufficient oxygen is available by the following equation:
C6H12O6 + 6O2 6H2O + 6CO2 + ATP
All organisms, including plants and animals, oxidize glucose for energy .Often this energy is used to convert ADP and phosphate into ATP.
- Plant leaves
- Logger pro software
- 500 mL beaker
- Vernier CO2 gas sensor
- Aluminum foil
- 250 mL respiration chamber
- Write a hypothesis below comparing the two conditions being tested
- Connect the CO2 Gas Sensor to the Vernier interface.
- Prepare the computer for data collection by opening the file “31B Photosyn-Resp (CO2)” from the Biology with Vernier folder of Logger Pro.
- Obtain 6g of evergreen leaves (from outside); blot them dry, if damp, between two pieces of paper towel.
- Place the leaves into the respiration chamber, using forceps if necessary. Wrap the respiration chamber in aluminum foil so that no light reaches the leaves.
- Place the CO2 Gas Sensor into the bottle as shown in Figure 1. Gently twist the stopper on the shaft of the CO2 Gas sensor into the chamber opening. Do not twist the shaft of the CO2 Gas Sensor or you may damage it. Wait 3 minutes before proceeding to Step 6.
- Click Collect to begin data collection. Data will be collected for 10 minutes; the program file will automatically connect data for 10 minutes.
- When collection has finished, determine the rate of respiration:
- Move the mouse pointer to the point where the data values begin to increase. Hold down the left mouse button. Drag the pointer to the point where the data ceases to rise and release the mouse button.
- Click on the Linear Fit button, to perform a linear regression. A floating box will appear with the formula for a best fit line.
- Record the slope of the line, m, as the rate of respiration in Table 1.
- Close the linear regression floating box.
- Move your data to a stored run. To do this, choose Store Latest Run from the Experiment menu.
- Remove the aluminum foil from around the respiration chamber.
- Fill a 500 mL beaker with water (not the respiration chamber) and place it between the lamp and the respiration chamber. The flask will act as a heat shield to protect the plant leaves; ensure the emitted light is pointing directly at the leaves in the chamber.
- Turn the lamp on. Place the lamp as close to the beaker with water as possible, which will be located directly in front of respiration chamber. Do not let the lamp touch the tissue culture flask. Note the time. The lamp should be on for 3 minutes prior to the beginning data collection.
- After the three-minute time period is up, click connect to begin data collection. Data will be collect for 10 minutes; the program file will automatically connect data for 10 minutes.
- When data collection has finished, determine the rate of photosynthesis:
- Move the mouse pointer to the point where the data values begin to decrease. Hold down the left mouse button. Drag the pointer to the point where the data ceases to decline and release the mouse button.
- Click on the Linear Fit button, to perform a linear regression. Choose “Latest: CO2” and a floating box will appear with the formula for a best fit line.
- Record the slope of the line, m, as the rate of photosynthesis in Table 1.
- Close the linear regression floating box.
- Remove the plant leaves from the respiration chamber, using forceps if necessary. Clean and dry the respiration chamber.
- Share your data with the class by adding it here (and on website), don’t add units to your numbers).
- Using the class data and averages, found here (and on website), create a graph to show average rate of photosynthesis for the two conditions (light and dark). Be sure to include error bars and to complete a t-test to compare the results of the two different conditions.
DATA COLLECTION & ANALYSIS
Table 1. Rate of CO2 intake or released (ppt/min) in Dark & Light Conditions
Rate of CO2 intake or released (ppt/min)
In the Dark
Data Table for Graph
Insert the data table(s) of class data used for graphs here:
Insert your graph here (video that shows you how to do this):
Compose a conclusion and evaluation based on the class data (consult the Evaluation Checklist and presentation that indicates what should be include
Lab Standard: Analysis
Lab Standard: Evaluation
A full explanation of the lab standard rubric can be found here