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Copy of Lab 6: Cellular Respiration
Transcript of Copy of Lab 6: Cellular Respiration
Chaminade Julienne High School
In this experiment, cellular respiration was affected by different factors, such as temperature. The purpose of this experiment is to measure the rate of oxygen consumption during cellular respiration. The study was done by using respirometers, or O2 gas sensors, to measure the rate at which water was entering the end after oxygen was being absorbed by the peas. The results were not very precise, having the data for the warm water proving to have less cellular respiration than the cold, but room temperature was correct according to our hypothesis. INTRODUCTION/Background Information
This experiment was done to explore the rate of cellular respiration by measuring the amount of oxygen consumption. Since there needed to be a controlled environment, respirometers were used to assure that the environment was as controlled as possible. Each respirometer had the same volume inside of it, which assured that one more variable was controlled. Since the dead peas had less volume, glass beads were added to it to make the volume the same to the germinating peas (volume was measured by the displacement of water in a graduated cylinder).
It was then hypothesized from this information that germinating peas would absorb more oxygen because they are just starting to live and need to perform cellular respiration to stay alive (Campbell). This was not true for the dead peas. Also, the increase in temperature, the more likely the peas would absorb oxygen, because the plant needs to maintain homeostasis. In lower temperatures, the molecules will be less likely to move and therefore less oxygen absorbed. Likewise, black eyed peas would absorb more oxygen because they have a greater surface area to volume ratio (packet. Will germinating or non-germinating peas affect the rate of oxygen absorption?
Hypothesis: The germinating peas will absorb more oxygen than non-germinating peas will.
1. Safety goggles, aprons, gloves
2. Germinating peas
3. Non-germinating peas
4. Glass beads
5. 3 rubber stoppers attached to
6. 3 glass cylinders with washers
7. Absorbent cotton
8. Non-absorbent cotton
9. 15% solution KOH
10. Food coloring
12. Graduated cylinder Will temperature affect the rate of oxygen absorption?
Hypothesis: As temperature increases, so will oxygen absorption increase.
Will using black eyed peas instead of regular peas affect the rate of cellular respiration?
Hypothesis: The black eyed peas will absorb more oxygen because they have a larger SA to volume ratio. References and Acknowledgments
Campbell, N.A., & Reece J.B. (2005). AP Edition: Biology. San Francisco, CA.
The College Board. (2012). AP Biology Investigative Labs: an Inquiry-Based Approach. New York, NY.
Ooten, A. Personal communication, October 18, 2012. Discussion
The results were that germinating peas absorbed more Co2 than non-germinating peas. This happened because the germinating peas were still growing, proving a need to absorb oxygen. Where the dead peas did not need to absorb oxygen because they were already dead. Temperature affects the peas, because, to stay alive, cellular respiration needs to be performed. Therefore, more oxygen would be absorbed when the plants were in warm water than when they were in cold water because the plants need to maintain homeostasis and the molecules of anything move faster in warm water versus cold water. In effect, cold water would make the molecules slow down and not work as efficiently.
This proves our data. Germinating peas absorbed much more oxygen, cumulatively, than non-germinating peas. Temperature decreased, and so did the absorption of oxygen. Vice versa, temperature increased and so did the absorption of oxygen. The black eyed peas was not tested, so there was no way of collecting data for that experiment.
Places where there could have been error, for example in the use of KOH. There was possibly not enough used, skewing the results of the absorption of oxygen. Also, there could have been some counting that was off when attempting to make the volume in each cylinder the exact same.
Ways to improve the experiment would be to make the displacement of volume even more exact or making sure that the KOH was soaking the absorbent cotton and that the amount of drops were counted accurately. Also, when displacing the peas, make sure not to leave them in the water too long, just in case they absorb the water and change the volume or ability to perform cellular respiration. To expand the experiment, another enzyme could have been used, different peas could have been used, invertebrates also could have been used instead of peas. A final way to differentiate the experiment would be to use a different, preferably longer, time period to measure rate of oxygen consumption.
There is also another factor to this. If the data shows that cellular respiration occurs more when an organism is placed in a cold environment, then how do molecules move faster causing cellular respiration to occur when the water is hot instead of being cold? At room temperature and warm temperature, cellular respiration would still be occurring, but just not as drastically than at colder temperatures. Conclusion
In conclusion, germinating peas absorb more oxygen (perform more cellular respiration) than non-germinating peas. Temperature can affect the rate of absorption
of oxygen, with higher temperatures causing
more absorption (more cellular respiration), and lower temperatures causing less absorption (less respiration). QUESTIONS TO ANSWER
1. Using the general gas law (state this law!) and your experience in this lab, give the variables that had to be controlled for your data to be valid. State the controls used for each variable and any means used to correct for the influence of a variable(s).
Pv= nRT. The variables were the volume inside the respirometer, shown in our displacing of the peas and then the adding of glass beads to keep the volume constant to correct any faulty results. Then temperature, which the respirometers had to get used to before the whole system could be completely placed in the water, and which could be measured only after oxygen had been absorbed. N, or number of moles, had to stay the same, so when CO2 was absorbed, O2 was taken in. No matter is created no destroyed. Pressure had to stay the same, so when there was less pressure inside of the respirometer, water was sucked in from the end.
2. From your graph, calculate the rate of oxygen consumption for each treatment:
a. Germ at room temp: 0
b. Germ at colder temp: 0.032
c. Germ at warmer temp: -0.002
d. Non Germ at room temp: -0.0016
e. Nongerm at colder temp: 0.004
f. Nongerm at warmer temp: -0.0014
3. If you used the same experimental design to compare the rates of respiration of a 25 g reptile and 25 g mammal at 10 degrees C, what results would you expect? Explain your reasoning.
The results I would expect would be that the mammal would absorb more oxygen, because, to maintain homeostasis and stay warm. The reptile, being cold blooded, only adapts to his environment but still absorbs a small amount of oxygen, but significantly less than the mammal.
4. If respiration in a small mammal were studied at both room temperature (21C) and 10C, what results would you predict? Explain your reasoning.
At 10C, the mammal would be performing more cellular respiration to stay warm and maintain homeostasis. At room temperature, though, the mammal would still be performing some cellular respiration and absorbing some oxygen, but less than it would at 10C. Methods
1. Place about 15 drops of KOH on the absorbent cotton
2. Push this down into the glass cylinder with the washers then take the non-absorbent cotton and push it down on top (do this two more times)
3. Count out 25 germinating peas
4. Take 25 mL of water in a graduated cylinder, put the 25 germinating peas into the cylinder to measure water displacement (record data)
5. Count out 25 non-germinating peas and put glass beads in the graduated cylinder along with the peas to get the same displacement as the germinating peas
6. Do the same for the glass beads to get the same displacement as the germinating peas
7. Put each amount of peas and/or glass beads in the glass holders and put the rubber stoppers in on top
8. Place in water (room temperature) and place the tips above the water in a tape sling
9. Put food coloring in the tip to show how far the water travels down
10. Place respirometers completely in the water, and record data every 5 minutes for 25 minutes