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CELL RESPIRATION A.P. LAB # 5 INTRODUCTION/BACKGROUND INFORMATION: In this lab our objective was to measure the rate of aerobic respiration over a time period of twenty minutes for germinating and nongerminating pea seeds. In this experiment we tested and measured the relative volume of oxygen consumption by the germinating and nongerminating peas in two different temperatures, a 25 degree Celsius atmosphere, and a 10 degree Celsius atmosphere. Aerobic cellular respiration is the release of energy from organic compounds by metabolic chemical oxidation, and it involves many enzyme-catalyzed reactions. There are three ways in which cellular respiration can be measured, but in this lab we focused on measuring oxygen consumption over a certain period of time using a respirometer. The respirometer was attached to our vials and the carbon dioxide produced during the cellular respiration was removed by potassium hydroxide (KOH) which we put in the bottom of our vials, however, not touching the peas. To make our data collection more accurate, we had a control vial filled with glass beads and this helped in keeping our data exact. MATERIALS: See lab packet 5 for the materials. PROCEDURE: See lab packet 5 for the procedure. DATA: Raw data from this lab is in the lab packet, and the graph and table are attached on page 8. ANALYSIS: 1. In this activity we investigated both the effect of germination versus nongermination and warm temperature versus cold temperature on respiration rate. Two hypotheses being tested in this activity are; the germinating peas will have a much higher rate of cellular respiration than the nongerminating (dry) peas, and the respiration rate will be higher in a warmer temperature versus a colder temperature. 2. This activity used many controls. They conditions that had to remain constant were temperature, volume, amount of cotton, amount of KOH, size of the respirometer, and the number of peas in each respirometer. Temperature must remain constant within the experiment because it will change the pressure in the respirometer. Total volume must remain constant because we wouldn’t be able to compare the three experiments if the volumes were not identical. Amount of cotton in each respirometer must remain constant because if not the volumes for each respirometer would be different. There needed to be the same amount of KOH in each respirometer so that the same amount of carbon dioxide is being removed from the vials. The size of the respirometers must be constant so that the volume is the same and temperature would be dispersed evenly. The number of peas in each respirometer must be constant so we can compare the three experiments, if one had more germinating peas, the volume would be different but also the oxygen consumption would change. 3. The independent variable was Time in minutes and the dependent variable was oxygen consumption in milliliters. The graph for this section is in the lab packet. 4. As the time increased, the amount of oxygen consumed also increased. From the data and the graph we can see an upwards trend of oxygen consumption versus time. The germinating peas had a much higher rate of cellular respiration than the nongerminating peas because in the graph the amount of oxygen consumption increased faster as time increased than the dry peas. 5. Condition Show Calculations Here Rate (mL Oxygen / minute) Germinating Peas / 10°C Germinating Peas / Room Temperature Dry Peas / 10°C Dry Peas / Room Temperature 6. It is necessary to correct the readings from the peas with the readings from the beads because the bead readings were the controls and they detected any change in volume due to atmospheric pressure changes or temperature changes caused by human error (letting the temperature fall, letting the sealed top come loose, etc.). If we did not correct the readings from the peas with the readings from the beads, none of the error factors would be taken into consideration when measuring the rate of respiration and the rate of respiration would therefore be inaccurate. 7. The effect on germination versus nongermination on pea seed respiration is very important. Germinating pea’s respirate at a faster rate than the nongerminating peas which is shown by their larger amounts of oxygen consumption. Nongerminating peas respirate somewhat, but not at the fast rate that germinating peas do. 8. I predict that as the temperature rises, the amount of O2 consumption would increase up until the peas begin approaching higher temperatures. When the peas start to approach higher temperatures, the enzymes involved in cellular respiration will have a harder time breaking down substances because they would denature when exposed to high heat as they are proteins. The peas will increase in oxygen consumption until they reach a peak at which they would perform cellular respiration at the optimum level, and then the oxygen consumption would decrease because the temperature would be too high for the enzymes involved in cellular respiration to function. The predicted graph is in the lab packet. 9. The purpose of KOH in this experiment is to remove carbon dioxide gas from the vials so not to disrupt the reading of oxygen consumption. They KOH does this by forming solid potassium carbonate, and this makes sure that the carbon dioxide gas does not interfere with the change of volume of gas in the respirometer for the amount of oxygen consumed. 10. The vial had to be completely sealed around the stopper for many important reasons. A loose stopper would have allowed water to leak into the vial. If water leaked into the vial, it would change the volume of the vial and ruin the data collected for that vial. If water leaked in pressure would also be affected, and if these important variables were altered, especially since they needed to remain constant, the data collected would be invalid and lead to an inaccurate conclusion of the experiment. 11. If I were to use the same experimental design to compare rates of respiration of a 25 g mammal and a 25 g reptile, I would expect the 25 g mammal to consume more oxygen than then 25 g reptile. I think this because the mammal is warm blooded, and just like the germinating peas in the warmer temperature, the oxygen consumption was higher in warmer temperatures. The reptile, however, is cold blooded so oxygen consumption would not be as high and similarly the rate of respiration would not be as high as in the mammal. The germinating peas were more active than the nongerminating peas which mean they needed, like the mammal, more oxygen consumed to have enough energy, in the mammal’s case, to have enough energy to stay warm. The cold blooded reptile can maintain a lower body temperature with less consumption of oxygen so this reaffirms that the 25 g reptile would consume less oxygen than the 25 g mammal. 12. If respiration in a small mammal were studied at both room temperature (21°C) and 10°C, I would predict the results to show that the respiration of the small mammal at 10°C would require more oxygen consumption than the small mammal at room temperature. I would predict this because of the mammal’s need to increase its body temperature to stay living. The small mammal at room temperature could maintain itself longer than the mammal at 10°C would be able to, and therefore the mammal at room temperature would need less energy, less oxygen consumed to run cellular respiration quickly, to maintain a stable body temperature. 13. The water moved into the respirometer’s pipettes because during the cellular respiration process, the oxygen is consumed and the carbon dioxide is produced. The production of carbon dioxide would react with KOH and form potassium carbonate. The volume of gas lost by the oxygen would then be replaced with water until the vial is once again full which is why the water would move into the respirometer’s pipettes. 14. If I designed an experiment to examine the rates of cellular respiration with peas that have been germinating or different lengths of time: 0, 24, 48, and 72 hours, I would expect results similar to the current lab. In the new experiment I would change the materials used. Because the objective is to find the rate for germinating peas, there would be no use for nongerminating peas. However, I would keep the vial with the glass beads as a control vial in case there is a pressure change. I would use only water baths at room temperature and the vials with the peas, cotton, KOH, and glass would be placed into the tubs to find out the oxygen consumption. During this time, several other vials would be tested for the amount of oxygen consumption for peas germinating for 0, 24, 48, and 72 hours. I think the result should be similar to the current lab because peas that have been germinating for a longer period of time would require more oxygen consumption during cellular respiration. Therefore, the newly germinating peas would show less O2 consumption when compared with the ones that had been germinating for longer. CONCLUSION: In this lab, our aim was to find the rate of aerobic respiration over a time period of twenty minutes for germinating and nongerminating pea seeds. In this experiment we measured the relative volume of oxygen consumption by the peas in a 25 degree Celsius atmosphere, and a 10 degree Celsius atmosphere. After doing this lab, we were able to calculate the rate of cellular respiration from experimental data, relate gas production to respiration rate, and understand the effect of temperature on the rate of cellular respiration in germinating versus nongerminating seeds in a controlled experiment. We also learned how to find the corrected difference which led us to have more accurate data. Overall we found that germinating pea’s respirate at a faster rate than the nongerminating peas which is shown by their larger amounts of oxygen consumption and therefore we found that nongerminating peas respirate somewhat, but not at the fast rate of germinating peas. This lab was helpful in reaffirming cellular respiration as extremely important to sustain life, I feel much more confident with the information because of this lab.
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