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Respirometer Lab

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Matt whalen

on 11 December 2013

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Transcript of Respirometer Lab

Materials and Methods
Analysis and Conclusion
Oxygen Respirometer Lab
To conduct our experiment, we first started off with pre-constructed respirometers. They were made out of syringes with hollow glass tubes attached to the end. We then placed absorbent cotton into the respirometer. We used the glass rod to push it down into the very bottom. Then we used a pipette to put 5 drops of potassium hydroxide (KOH) on to the cotton. After that we placed non absorbent cotton into the end and then placed 5 barley seeds into the respirometer. We filled a cup with slightly warm water, allowed it to equilibrate to the room temperature, then submerged our complete respirometer with the barley seeds in the water. We used a pipette to place a single drop of red dye into the tip of the respirometer and began our stopwatch. At 30 second intervals we measured how much oxygen had respired using a ruler and measuring in millimeters. We kept measuring until 4 minutes had passed, 50 mm of oxygen had respired, or the respiration ceased. We repeated this test twice and recorded our results. We then repeated the process, but cut the barley seeds in half using a razor. We used the same number of seeds, all cut in half, totaling 10 half seeds. The exact process was the same except for this detail. Also a negative control test was conducted with cork to ensure the accuracy of the results.
Every cell in a living object must be responsible for the energy exchanges in that organism. The conversion of Oxygen and Glucose to Carbon Dioxide, Water, and energy (in the form of ATP) is the exchange known as cellular respiration. In order to learn more about these processes, specifically rates of cellular respiration, we conducted an experiment to see how it could be manipulated or affected.
Our hypothesis was centered around the effects of surface area on respiration rate. In our initial baseline tests, we used whole seeds to measure respiration. We decided that we wanted to test how increasing the surface area of the seeds would change how quickly they respired. It is pretty well established that an increase in surface area in cells will increase their rate of exchange with their environments.
Based on our last lab experiments, we found that increasing the surface area of agar blocks had the same effect. We were intrigued by this process and wanted to see if it would hold true for barley seeds. Since we were cutting an entire seed in half, it is not increasing the surface area of many cells. Rather, it increases the surface area of the seed as a whole, and exposes many cells on the inside of the seed to the outside environment. We hypothesized that this would produce results similar to those we found in our previous experiment, and that the rate of respiration would increase, if only slightly.
Our baseline results indicated that our respirometers were working correctly. We conducted two baseline tests that respired at similar rates. This seemed to show that there was a semi-constant rate of respiration for the 5 barley seeds. We also did a negative control test using cork to ensure that our respirometers were not supplying false data. The cork did not cause a change in 02 levels and therefore supported our findings.
Hypothesis Tests
The results of our tests at first seemed to support our hypothesis. The seeds with increased surface area respired much more quickly than the first baseline, and almost as quickly as the second. We expected it to follow this trend, but after two minutes the seeds with more surface area stopped respiring almost completely. The consumed oxygen levels tapered off at about 37 mm and 27 mm for the first and second tests respectively. When compared side-by-side, it is clearly visible that there a drop in respiration rate for the surface area tests. Instead of following what we hypothesized, they actually did almost the opposite. They started off with a fast rate of respiration and ended much slower, whereas the baseline tests remained at a fairly constant rate throughout the duration of tests. We believe that the reason this happened could be attributed to design flaws in our experiments, mistakes in executing them, or a flawed hypothesis from the start. No matter what the cause, it seems that our hypothesis was disproved.
As seen in the graph, the surface area tests started off pretty quickly. Each of the surface area tests started off faster than the first baseline, and were slightly slower than the second baseline. However, even though they got off to a strong start, after a minute and a half they started to respire much slowly. After two and a half minutes there was very little change until the end of the tests.
The surface area tests started off at a quick rate of respiration. However, following the two minute mark, they quickly dropped off and became almost, or completely, stagnant.
Our experiment was conducted with the goal of gathering data about rates of respiration, and seeing what changes and effects could be made. We used respirometers to measure how quickly oxygen respired in barley seeds. We conducted two baseline tests, as well as a negative control test. We then formulated a hypothesis which was focused on increasing respiration in correlation with an increased surface area. We tested this hypothesis twice, in the same manner as the baseline. After we had finished and gathered all our data, we analyzed it to see what our findings showed and what interpretations could be made. Our findings ultimately did not support our hypothesis, but there was still much that we discovered about influencing cellular respiration.
Our hypothesis that larger surface area increases the rate of respiration was disproved after the results of our testing were analyzed. This means that in this particular instance, surface area did not affect the cellular respiration rate. Outside factors could have tampered with our results. Water temperature made the respiration rate increase if the water was too cold and made the rate slow down if it was too warm. We learned that the environment in which the testing was completed in could have played a role in the results which were achieved. Also the factors of the ideal gas laws (temperature and pressure) came into play and our group did not consider them as much as we should have. In future tests having a standard exact water temperature could possibly contribute to achieving more accurate results.
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