Cellular Respiration Lab

Cellular Respiration: Using the Vernier LabQuest to detect CO2 gas production in germinating peas

DESIGN

Research Question:
What is the effect of temperature on CO2 gas production in germinating peas?

Background: The process of cellular respiration, which provides energy for cell growth and development, is an important part of life in germinating seeds. It converts the chemical energy of glucose into ATP. As a germinating seed respires, CO2 is produced as a byproduct. Therefore, the amount of CO2 produced from a respiring seed can be an indicator of the amount of activity that is taking place in its cells. Germinating peas in particular undergo cellular respiration in their early stages of development, as they are often buried
underground where there is no light present for photosynthesis to take place. For germinating peas, cellular respiration is a necessary component of growth and survival. The aim of this experiment is to investigate the effect of temperature of CO2 production in germinating peas.

Hypothesis: My hypothesis is that the germinating peas that are placed under a significantly cold temperature will, in general, produce less CO2 than the peas that are left at room temperature because this would denature the enzymes that are necessary for the cells of the peas to function.
Secondly, I predict that CO2 production will increase with temperature until a certain point. Germinating peas have an optimal temperature for respiration. However, when the temperature increases significantly past optimal, it is possible that enzymes will denature, hindering or perhaps fully halting CO2
production.

Variables

Experimental Variables Units used to measure
Independent variable: temperature Degrees Fahrenheit
Dependent variable: CO2 gas production in germinating peas PPM
Relevant controlled variables Effects of the variables on the outcome of the experiment if we ignored them Plan to control these variables
Size of peas Germinating peas can vary in size which can affect total CO2 production Peas will be handpicked to be about the same size so that no significantly small or larger peas are used.
Time peas have been germinating Peas that have been germinating at different lengths of time can have an effect on CO2 production because as they grow, they begin to rely more on photosynthesis and less on respiration All peas that are used will have been left to germinate for the same amount of time
Wait time before Labquest begins collecting data Time between equilibration and selecting ‘play’ on Labquest for data collection may vary. Data may be collected for different time periods in CO2 production. During the one-minute equilibration period, the Labquest will be set up so that data collection begins as close to the end of the equilibration period as possible.

Materials

- 5 LabQuest data collection programs
- 5 CO2 gas sensors
- 5 250 mL respiration chambers (bottles)
- Paper towels
- 125 germinating peas
- A few handfuls of glass beads
- Timer
- 5 plastic tubs
- Ice cubes
- One water bath
- Thermometer measuring degrees Fahrenheit

Methods

1. A total of 125 germinating peas will be obtained, being wary of size. I will attempt to pick peas that are all of a similar size.
2. I will separate the germinating peas into 5 groups of 25 and mass one group using water displacement. Then I will obtain this same mass of glass beads and place these in one group, labeling each group 1 through 6.
3. Preparing the peas:
a. Cold peas:
i. One group of 25 germinating peas will be soaked in a plastic tub filled with ice water for 15 minutes
1. The temperature of the water will be recorded in degrees Fahrenheit in Table 1. ii. One group of 25 germinating peas will be soaked in cold tap water for 15 minutes
1. The temperature of the water will be recorded in degrees Fahrenheit in Table 1.
b.
Warm peas:
i. One group of 25 germinating peas will be soaked in a hot water bath for 15 minutes
1. The temperature of this water will be recorded in degrees Fahrenheit in Table 1. ii. One group of 25 germinating peas will be soaked in warm tap water for 15 minutes
1. The temperature of the water will be recorded in degrees Fahrenheit in Table 1.

c. Room temperature peas:
i. One group of 25 germinating peas will be soaked in a tub filled with room temperature water for 15 minutes
1. The temperature of this water will be recorded in degrees Fahrenheit in Table 1. ii. The glass beads will be soaked in a tub filled with room temperature water for 15 minutes
1. The temperature of this water will be recorded in degrees Fahrenheit in Table 1.

4. I will locate the switch on the CO2 gas sensor to the low setting (0-10,000 parts per million [ppm])
5. Next, I will connect the gas sensor into one of the ports in the top of the Labquest
6. Using a stylus, the Labquest will be turned on. New will be selected from the file menu to start a new data collection
7. 25 room-temperature peas will be blotted dry between paper towels
8. The peas will be placed in the respiration
chamber
9. The CO2 gas sensor will be placed snugly into the top of the respiration chamber
10. Next, I will wait one minute for the peas to equilibrate (use a timer to ensure accurate equilibration time)
a. During this equilibration period, data collection will be set up
i. Select the meter icon on the Labquest screen using the stylus ii. Sensor and then Data collection will be selected iii. The collection length should be set to 300 seconds with a rate of 2 samples per second
11. After the minute allocated for equilibration is up, I will begin data collection by selecting the graph icon at the top of the screen and selecting Play.
12. When the data collection has finished, I will carefully remove the CO2 gas sensor from the respiration chamber and will fan the opening of the chamber for one minute
13. The peas will be then be returned to the teacher
14. Next, I will calculate a linear regression in order to find the rate of respiration:
a. Curve fit will be chosen from the analyze menu as the graph form data collection is displayed
b. Linear for fit equation will be selected. Statistics will be displayed in the form Statistics will be displayed in the form y=mx+b where x is the time in seconds, y is the CO2 concentration in ppm, m is the rate of respiration, and b is the y-intercept.
15. Rate of respiration will be recorded in Table 1.
16. Steps 4 through 15 will be repeated twice for a total of three trials per group.
17. Steps 4 through 16 will be repeated with each group of peas and glass beads.

Figure 1: Connecting CO2 gas sensors to LabQuest

RAW DATA

Table 1: CO2 production of germinating peas at varying temperatures Note: due to time constraints, groups 5 and 6 were not measured.

Peas or glass beads? Temperature of water in degrees Celsius (+/- 1) Rate of respiration:
CO2 production in ppm/s
(+/- 100ppm) Average rate of respiration
(+/- 100 ppm) Trial 1 Trial 2 Trial 3 Trial 1 Trial 2 Trial 3
Group 1
Group 2
Group 3
Group 4
Group 5
Group 6

PROCESSED DATA

Table 2: Averaged CO2 production of germinating peas at varying temperatures

Peas or glass beads? Average temperature of water in degrees Celsius (+/- 1) Average rate of respiration: CO2 production in ppm/s
(+/- 100 ppm)
Group 1 Peas 41 4.304
Group 2 Peas 8 3.857
Group 3 Peas 19 3.287
Group 4 Glass beads 19 0.358

CONCLUSION

The effect of temperature on CO2 gas production in germinating peas is that as temperature increases, the amount of CO2 produced from germinating peas increases. This was correctly predicted in the hypothesis. However, CO2 also increased when there was a decrease in temperature. As shown in Table 2, of the three ranges that tested germinating peas, the room temperature peas produced the least CO2. Peas that had been soaked in water at a temperature of 40 degrees Celsius yielded an average rate of respiration of 4.304 CO2 ppm per second, while the peas that had been soaked in water at 8 degrees Celsius showed an average rate of respiration of 3.857 CO2 ppm per second. The peas that had been soaked in room temperature water, on the other hand, respired at a rate of 3.287 ppm per second. This disproves the original prediction that a decrease in temperature slows cellular respiration in germinating peas. This decrease in CO2 production may be due to a variety of reasons. The fact that the group soaked in warm water respired the most is logical. Enzymes that catalyze reactions inside the cells of the peas have an optimum temperature, where activity increases until a certain temperature, where, if exceeded, enzymes that are required for the metabolic processes of the cell are denatured (‘Enzymes’). Additionally, molecules generally tend to move faster at higher temperatures, which would have supported an increase in enzymatic activity when the peas had been soaked in warm water (Banas). A higher amount of carbon dioxide respired from the peas suggests that the optimal temperature had not been surpassed- the cells of the peas were still active and respiring. The increase in CO2 production implies that the optimum temperature for the cells of the peas tends to be warmer.

The fact that the peas soaked in water at 8 degrees Celsius respired on average at a rate of 0.67 ppm/s faster than the peas soaked in room temperature water, however, does not support the theory that an increase in temperature caused an increase in CO2 production, nor does it support the hypothesis. This may be due to a variety of reasons. Firstly, as shown in Table 1, both the room temperature peas and the cold peas tended to be much more inconsistent in CO2 production when compared to the warm peas. Each trial of the cold peas decreased significantly from the trial before it, yielding a difference of 5.07 ppm/s between the trial 1 and trial 3. Room temperature peas also showed inconsistent results- trial 1 indicated a rate of 4.144 ppm/s, while the rate of trial 3 was 3.116 ppm/s less. The control group of glass beads, on the other hand, was much more consistent. Very little CO2 was produced from the control group, as expected. The unexplained decrease in CO2 production, combined with a much more consistent control group, suggests that there were issues with reliability in the execution of the experiment.

EVALUATION AND IMPROVEMENTS

There are a number of improvements that could be made in the experiment that could improve reliability of the data. The main weakness in this experiment was lack of time. The peas were left for about 72 hours to germinate, which was an adequate amount of time, however there was not enough time during class to test all five groups of germinating peas as well as a control group. Instead, three groups were tested at a range of temperatures, and one control group was tried at room temperature. If I were doing this experiment again, I might complete it at home so that I would have much more time to test all the temperatures that I had planned to. This lack of time may have decreased reliability of the results in other ways. While the respiration chambers were being set up, my lab partner and I were hurried. This caused us to knock over the respiration chambers a few times as data was being collected, which may have skewed results. An overall longer amount of time to _ the experiment would have allowed more time to complete additional trials, as well. As shown in Table 1, raw data, there were major variations in rate of respiration between trials. For example, in Group 2, Trial 1 yielded a rate of 6.338 ppm/s, while Trial 2 yielded a rate of 1.268 ppm/s. These fluctuations may have been caused by changing temperatures in the classroom, as volume of a gas is greatly affected by the surrounding air temperature.

One other major weakness of the experiment was that the one-minute equilibration period that was allowed while the data collection software was being set up did not happen as planned. This equilibration period was supposed to allow the peas some time to begin respiring at a steady rate before data collection began. The LabQuest that we chose was not receiving data from the fourth probe, so we had to find another LabQuest, plug it in again, and prepare it to collect data. This caused the equilibration period during the first experimental trial to last four minutes more than the originally planned one minute. While this may not have greatly affected the rate of respiration, it would have caused data collection to begin when much more CO2 had been given time to accumulate in the respiration chamber. This is shown in comparing Figure 2 (graph for trial one) and Figure 3 (graph for trial 2). In trial one, for example, the intercept with the y-axis for probe one was 3031 ppm, while the y-intercept for probe two was 1867 ppm. As the y-axis shows the amount of CO2 present in the respiration chamber when data collection begins, this suggests that equilibration time has an effect on the amount of CO2 in the chamber. To prevent against this error in the future, I would test the LabQuest that I planned to use to ensure equilibration time is kept as a constant.

WORKS CITED

Banas, Timothy. "The Effect of Temperature on Pea Respiration." GardenGuides. N.p., n.d. Web. 17 Dec. 2013.

"Enzymes." Chemistry for Biologists:. N.p., n.d. Web. 16 Dec. 2013.