Cell Respiration

Cell Respiration Samantha A. Price AP Biology 10-26-09 Lab #3

Introduction: If the temperature is lower, then there will be less respiration preformed. The experiment calls for dormant seeds. These seed are living but do not have sufficient conditions to grow into plants. Seeds contain an embryo plant and a food supply surrounded by a seed coat. When conditions are met, germination occurs and the rate of respiration increases (Lab sheet overview). Aerobic cellular respiration is the release of energy form organic compounds by metabolic chemical oxidation in the mitochondria within each cell. Cellular respiration involves a series of enzyme-mediated reactions. Cellular respiration can be measured in three ways consumption of O2, production of CO2, or release of energy during cellular respiration. All of these measurement methods can be seen when looking at the equation for cellular respiration. C6H12O6+6O2  6CO2+6H2O+686 kilocalories of energy/mole of glucose oxidized

PV=nRT must also be understood to conduct this experiment (P being pressure of the gas, V being the volume of the gas, n being the number of molecules of gas, R being the gas constant, and T the temperature of the gas in degrees Kelvin). This simple equation tells important concepts about gas such as: 1. If the temperature and pressure are kept constant, then the volume of the gas is directly proportional to the number of molecules of the gas. 2. If the temperature and volume remain constant, then the pressure of the gas changes in direct proportion to the number of molecules of gas present. 3. If the number of gas molecules and the temperature remain constant, then the pressure is inversely proportional to the volume. 4. If the temperature changes ant the number of gas molecules is kept constant, then either the pressure or volume (or both) will change in direct proportion to the temperature. Keeping in mind that both gasses and fluids flow from regions of high pressure to reasons of low pressure. Materials & Procedures: • • • • • • • • • • • • •

Tub 3 graduated cylinders Glass beads Germinating peas Cotton that is absorbent Cotton that isn’t absorbent KOH Dry Peas 3 weights 3 pipettes Thermometer Sling 3 stoppers

1. Both a room-temperature bath (by convention, 25ºC) and a 10ºC bath should be set up immediately to allow time for the temperature of each to adjust. Add ice to attain 10ºC. 2. Respirometer 1: Obtain a 100m: graduated cylinder and fill it 50mL of H2O. Drop 25 germinating peas in the graduated cylinder and determine the amount of water that was displaces (which is equivalent to the volume of the peas). Record the volume of the 25 germinating peas. Remove these peas and place them on a paper towel. They will be used in respirometer 1. PEA VOLUME __5__ mL 3. Respirometer 2: Refill the graduated cylinder with 50mL of H2O. Drop 25 dried peas (not germinating) into the graduated cylinder and then add enough glass beads to attain a volume equivalent to that of the expanded germinating peas. Remove these peas and beads and place them on a paper towel. They will be used in respirometer 2. 4. Respirometer 3: Refill the graduated cylinder with 50 mL of H2O. Determine how many glass beads would be required to attain a volume equivalent to that of the germinations peas. Remove these beads and place them on a paper towel. They will be used in respirometer 3. 5. To assemble the three respirometers, obtain 3 vials, each with an attached stopper and pipette. Place a small piece of cotton in the bottom of each vial and, using a dropper, moisten the cotton with 15% KOH. Make sure that the respirometer vials are dry on the insides. Do not get KOH on the sides of the respirometer. Place a small wad of nonabsorbent cotton on top of the KOHsoaked absorbent cotton making sure that amounts of KOH are the same for each respirometer.

6. Place the 1st set of germinating peas, dry peas plus beads, and beads in vials 1,2, and 3, respectively. Insert the stopper fitted with calibrated pipette. Place a weighted collar on each end of vial.

7. Make a sling of making tape attached to each side of each of the water baths to hold the pipettes out of the water during an equilibration period of seven minutes. Vials being either at room temperature or 10ºC. 8. After the equilibration period of seven minutes, immerse all respirometers entirely in their water baths. Water will enter the pipettes for a short distance and then stop. If the water continues to move into a pipette, check for leaks in the

respirometer. Work swiftly and arrange the pipettes so that they can be read through the water at the beginning of the experiment. They should not be shifted during the experiment. Hands should be kept out of the water bath after the experiment has started. Make sure that a constant temperature is maintained. 9. Allow the respirometers to equilibrate for three more minutes and then record, to the nearest 0.01 mL, the initial position of water in each pipette (time)). Check the temperature in both baths and record in table. Ever 5 min for 20 min, take reading of the water’s position in each pipette and record the data in table.

Results, Data Collection & Analysis:

Time Temp ºC (min)

10

0 5 10 15 20

Beads Alone

Germinating Peas Dry Peas and Beads Dif Reading at time Diff Reading at time f Corrected Diff Reading at time Diff Corrected Diff 5.1 NA 5.5 NA NA 2.9 NA NA 5.1 0 5.4 0.1 0.1 2.9 0 0 5.2 -0.1 5.2 0.3 0.4 3.1 0.2 -0.1 5.5 -0.4 5.2 0.3 0.7 3.6 -0.7 -0.3 5.6 -0.5 5.4 0.1 0.6 4.3 -1.4 -0.9

Figure 1 (team Sarah table of data)

Room temp 10ºC Team Tag Team Fro Team Emily Team Sarah Time (min) Peas Peas and beads Peas Peas and beads Peas Peas and beads Peas Peas and beads 5 -1.3 -1.4 0.1 0 -2.7 -3 0.1 0 10 -2.5 -2.5 -0.2 -0.2 -0.5 -0.2 0.4 -0.1 15 -3.2 -4.6 -0.5 -0.3 -3.3 -3 0.7 -0.3 20 -4.7 -7.1 -0.1 -0.4 -4.8 -3.9 0.6 -0.9

Figure 2 (class data)

Average at Room Average at 10ºC temp (18ºC) Time (min) Peas Peas and beads Peas Peas and beads 5 1.4 1.5 0.7 0.7 10 0.45 0.15 1.35 1.35 15 1.85 1.65 1.85 2.45 20 2.7 2.4 2.85 3.75

Figure 3 (average of class data)

Peas at 10ºC preformed less respiration than those at room temperature . Discussion & Conclusions: This experiment shows that the lower the temperature the less reparation is preformed. Though the data proves the hypothesis there were some errors in the group’s data (making not that the group is a 3rd party group that the data and notes were taken from). There was a leak in the pipettes and the type of pea could also be an error factor because northern gown peas germinate better at colder temperatures because their DNA is adapted to the temperatures. Literature Citaion: 1. Lab sheet 2. Class discussion Questions: 1. In this activity you are investigating both effect of germination versus no germination and warm temp versus cold temp on respiration rate. Identify two hypotheses being tested in this activity. a. If the temp is colder then the seeds will germinate less. b. Cellular respiration will occur in the germination peas because the peas are growing. Cellular respiration will hardly occur in the non-germination peas, because they aren’t growing, but there may be some bacteria on the outside of the peas. 2. This activity uses a number of controls. What condition must remain constant? Why? a. Volume, temp, beads, water temp, dormant seeds

It must remain constant so one can prove a hypothesis with various temperatures in other group’s testing. 3. Describe and explain the relationship between the amount of O2 consumed and time. a. As time increases O2 consumed, on average, increased as well. 4. Why is it necessary to correct the reading from the peas with the reading from the beads? a. Correcting for volume being taken up and what reparation would be done even without the peas due to bacteria and other tings also doing respiration. 5. Explain the effect of germination (versus non-germination) on pea sees respiration. a. Germination raises the respiration in peas. 6. What is the purpose of KOH in this experiment? a. It combines with CO2 to form a solid precipitate (KCO3). This also creates a pressure vacuum. 7. Why did the vial have to be completely sealed around the stopper? a. Water moved in the wrong direction due to gas build up in the vial before moving ingot the pipette because of an insufficient seal. 8. If you used the same experimental design to compare the rates of respiration of a 25g reptile and 25g mammal at 10ºC, what results would you expect? Explain your reasoning. a. The mammal’s cellular respiration would increase because it is trying to maintain its body temp (homeostasis). The reptiles respiration would slow because it’s a cold blooded animal and cannot adapt to cold temperatures. 9. If respiration in a small mammal were studied at both room temperature and 10ºC what results would you predict? Explain your reasoning. a. The small mammal needs to stay warm to survive, so it has to do more cellular respiration just to remain warm. 10. Explain why water moved into the respirometers’ pipettes. a. Water moves to areas of lower pressure when temp and volume are constant. Oxygen is consumed during respiration. Volume goes down, CO2 turns to solid. Gas volume in tube goes down and pressure goes down.