Computer
31C
Photosynthesis and Respiration
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.
C
op
y
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:
6 H2O + 6 CO2 + light energy C6H12O6 + 6 O2
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 + 6 O2 6 H2O + 6 CO2 + energy
OBJECTIVES
tio
In this experiment, you will
n
All organisms, including plants and animals, oxidize glucose for energy. Often, this energy is
used to convert ADP and phosphate into ATP.
 Use an O2 Gas Sensor to measure the amount of oxygen gas consumed or produced by a
Ev
al
ua
plant during respiration and photosynthesis.
 Use a CO2 Gas Sensor to measure the amount of carbon dioxide consumed or produced by
a plant during respiration and photosynthesis.
 Determine the rate of respiration and photosynthesis of a plant.
Figure 1
Biology with Vernier
31C - 1
Computer 31C
MATERIALS
computer
Vernier computer interface
Logger Pro
Vernier O2 Gas Sensor
Vernier CO2 Gas Sensor
BioChamber 2000
aluminum foil
ringstand
utility clamp
12-inch ring fluorescent lamp setup
spinach leaves
PROCEDURE
1. Wrap the BioChamber with aluminum foil so that no light will reach the leaves.
a. Wrap the outside of the chamber with foil.
b. Cover the lid with foil, poking the holes open to insert the sensors.
2. Cover the bottom of the chamber with one layer of fresh turgid spinach leaves. Remove any
stems that could interfere with an even lining of the bottom.
3. If your CO2 Gas Sensor has a switch, set it to the Low (0–10,000 ppm) setting. Connect the
CO2 Gas Sensor to Channel 1 and the O2 Gas to Channel 2 of the Vernier computer interface.
4. Prepare the computer for data collection by opening the file “31C Photo (CO2 and O2)” from
the Biology with Vernier folder of Logger Pro.
5. Secure the lid on the chamber and insert the sensors into the holes.
6. Wait five minutes for the sensors to equilibrate, then click
data collection.
to begin the 15-minute
7. When data collection is complete, determine the rate of respiration.
a. Click anywhere on the CO2 graph. Autoscale the data by clicking the Autoscale button on
the toolbar.
b. Move the cursor to the point where the data values begin to increase. Hold down the left
mouse button and drag the cursor to select the region of increasing CO2 gas concentration.
c. Click on the Linear Fit button, , to perform a linear regression. A box will appear with
the formula for a best fit line.
d. Record the slope of the line, m, as the rate of respiration in Table 1.
e. Close the linear regression box.
f. Repeat Steps 7a–e for the O2 graph, selecting the region of decreasing O2 concentration.
8. Store your data by choosing Store Latest Run from the Experiment menu.
9. Assemble the lamp as shown in Figure 1. Important: Do not turn the lamp on until
instructed to do so.
10. Remove the aluminum foil from the respiration chamber and invert the chamber to remove
the leaves and accumulated gases.
11. Line the bottom of the chamber with fresh turgid spinach leaves.
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Biology with Vernier
Photosynthesis and Respiration
12. Secure the lid on the chamber and insert the sensors into the holes.
13. Place the chamber inside the bulb and turn on the lamp.
14. Repeat Steps 6–7 to collect and analyze data.
15. Print a graph showing your photosynthesis and respiration data.
a. Label each curve by choosing Text Annotation from the Analyze menu. Enter
“Photosynthesis” in the edit box. Repeat to create an annotation for the “Respiration”
data. Drag each box to a position near its respective curve. Adjust the position of the lines
to indicate which curve is which.
b. Print a copy of the graph, with both data sets displayed.
16. Clean and dry the chamber.
DATA
Table 1
Leaves
CO2 rate of
production/consumption
(ppt/min)
O2 rate of
production/consumption
(ppt/min)
In the dark
In the light
QUESTIONS
1. Was either of the rate values for CO2 a positive number? If so, what is the biological
significance of this?
2. Was either of the rate values for O2 a negative number? If so, what is the biological
significance of this?
3. Do you have evidence that cellular respiration occurred in leaves? Explain.
4. Do you have evidence that photosynthesis occurred in leaves? Explain.
5. List five factors that might influence the rate of oxygen production or consumption in leaves.
Explain how you think each will affect the rate?
EXTENSIONS
1. Design and perform an experiment to test one of the factors that might influence the rate of
oxygen production or consumption in Question 5.
2. Compare the rates of photosynthesis and respiration among various types of plants.
Biology with Vernier
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Vernier Lab Safety Instructions Disclaimer
THIS IS AN EVALUATION COPY OF THE VERNIER STUDENT LAB.
This copy does not include:
z
Safety information
z
Essential instructor background information
z
Directions for preparing solutions
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Important tips for successfully doing these labs
The complete Biology with Vernier lab manual includes 31 labs and essential teacher
information. The full lab book is available for purchase at:
http://www.vernier.com/cmat/bwv.html
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