C6Hi (g) 6 H2O + 6 C02(g) + energy

Transcription

1 Experient Cell Respiration 110 Cell respiration refers to the process of converting the cheical energy of organic olecules into a for iediately usable by organiss. Glucose ay be oxidized copletely if sufficient oxygen is available, by the following equation: C6Hi (g) 6 H2O + 6 C02(g) + energy All organiss, including plants and anials, oxidize glucose for energy. Often, this energy is used to convert ADP and phosphate into ATP. To easure the rate of cell respiration, the pressure change due to the consuption of oxygen by peas will be easured. It is not possible to directly easure pressure changes due to oxygen, since the pressure sensor easures the total pressure change. Carbon dioxide is produced as oxygen is consued. The pressure due to CO2 ight cancel out any change due to the consuption of oxygen. To eliinate this proble, a cheical will be added that will selectively reove CO2. Potassiu hydroxide, KOH, will cheically react with CO2 by the following equation: 2 KOH + CO2 -> K2CO3 + H20 This will allow you to onitor pressure changes exclusively due to the consuption of oxygen. A respiroeter is the syste used to easure cell respiration. Pressure changes in the respiroeter are directly proportional to a change in the aount of gas in the respiroeter, providing the volue and the teperature of the respiroeter do not change. If you wish to copare the consuption of oxygen in two different respiroeters, as we will in this experient, you ust keep the volue and teperature of the air equal in each respiroeter. Both gerinating and non-gerinating peas will be tested. Additionally, cell respiration of gerinating peas at two different teperatures will be tested. OBJECTIVES In this experient, you will Use a coputer and a Gas Pressure Sensor to easure pressure changes. Study the effect of teperature on cell respiration. Deterine whether gerinated and non-gerinated peas respire. Copare the rates of cell respiration in gerinated and non-gerinated peas. Figure 1 Biology with Coputers 11C-1

2 MATERIALS coputer Vernier coputer interface LoggerPro 2 Vernier Gas Pressure Sensors 15% KOH in a dropper bottle 25 gerinating peas 25 non-gerinating peas 100 L graduated cylinder absorbent cotton forceps 2 utility claps glass beads ice non-absorbent cotton theroeter test tube rack tier with a second hand three 18 xl50 test tubes two 1-hole rubber stopper asseblies two 1 L beakers ring stand PROCEDURE 1. Connect the plastic tubing to the valve on the Gas Pressure Sensor. 2. Connect the Gas Pressure Sensor to the coputer interface. Prepare the coputer for data collection by opening the file "11C Cell Resp (Pressure)" fro the Biology with Coputers folder of LoggerPro. To test whether gerinating peas undergo cell respiration, you will need to set up two water baths. prepare a respiroeter for the gerinating peas. prepare a second, control respiroeter containing glass beads. 3. Set up two water baths, one at about 250C and one at about 10oC. Obtain two 1 liter beakers and place about 800 L of water in each. Add ice to attain the 10oC water bath. 4. To be sure the volues of air in all respiroeters are equal, you will need to easure the volue of the twenty-five peas that will be in the experiental respiroeter. The control respiroeter ust have an equal volue of glass beads (or other non-oxygen consuing aterial) to ake the air volue equal to the respiroeter with gerinating peas. Siilarly, glass beads will be used to account for any volue difference between the gerinating and non-gerinating peas. 5. Obtain three test tubes and label the "Tl", T2", and "T3".. 6. Place a 3 c wad of absorbent cotton in the botto of each test tube. Using a dropper pipette, carefully add a sufficient aount of KOH to the cotton to copletely saturate it. Do not put so uch that liquid can easily run out of the tube. Note: Do not allow any of the KOH to touch the sides of the test tube. The sides should be copletely dry, or the KOH ay daage the peas. CAUTION: Potassiu hydroxide solution is caustic. Avoid spilling it on your clothes or skin. 11C-2 Biology with Coputers

3 Cell Respiration 7. Prepare the test tube containing gerinating peas (Tl): a. Add 50 L of water to a 100 L graduated cylinder. b. Place 25 gerinating peas into the water. c. Measure the volue of the peas by water displaceent. Record that volue in Table 1. d. Gently reove the peas fro the graduated cylinder and blot the dry with a paper towel. e. Add a sall wad of non-absorbent dry cotton to the botto of the test tube to prevent the peas fro touching the KOH saturated cotton. f. Add these gerinating peas to the respiroeter labeled "Tl". 8. Prepare the test tube containing non-gerinating peas (T2): a. Refill the graduated cylinder with 50 L of water. b. Place 25 non-gerinating peas into the water Peas c. Measure the volue of the peas by water displaceent. Record the i rn t-i -i Cotton non-absorbent volue in Table 1. d. Add a sufficient nuber of glass beads to the non-gerinating peas and water until they displace exactly the sae volue of water as the gerinating peas. Cotton with KOH e. Gently reove the peas and glass beads fro the graduated cylinder and dry the with a paper towel. tigure z f. Add a sall wad of dry non-absorbent cotton to the botto of the test tube to prevent the peas fro touching the KOH saturated cotton. g. Add the non-gerinating peas and glass beads to the respiroeter labeled "T2". 9. Prepare the test tube containing glass beads (T3): a. Refill the graduated cylinder with 50 L of water. b. Add a sufficient nuber of glass beads to the water until they displace exactly the sae volue of water as the gerinating peas. c. Reove the glass beads fro the graduated cylinder and dry the. d. Add a sall wad of dry non-absorbent cotton to the botto of the test tube to prevent the peas fro touching the KOH saturated cotton. e. Add the glass beads to the respiroeter labeled "T3". Part I Gerinating peas, roo teperature 10. Insert a single-holed rubber-stopper into test tube Tl and T3. Note: Firly twist the stopper for an airtight fit. Secure each test tube with a utility clap and ring-stand as shown in Figure 1. Biology with Coputers lie-3

4 Experient 11C Arrange test tubes T1 and T3 in the war water bath using the apparatus shown in Figure 1. Incubate the test tube for 10 inutes in the water bath. Be sure to keep the teperature of the water bath constant. If you need to add ore hot or cold water, first reove about as uch water as you will be adding, or the beaker ay overflow. Use a basting bulb to reove excess water. Record the resulting teperature of the water bath once incubation has finished in Table 2. Note: Be sure the tubes are suberged to an equal depth, just up to the rubber stoppers. The teperature of the air in the tube ust be constant for this experient to work well. When incubation has finished, connect the free-end of the plastic tubing to the connector in the rubber stopper as shown in Figure 3. Click 1collect to begin data collection. Maintain the teperature of the water bath during the course of the experient. ip flp 14. Data collection will end after 20 inutes. Monitor the pressure readings displayed in the live readouts on the toolbar. If the pressure exceeds 130 kpa, the pressure inside the tube will be too great and the rubber stopper is likely to pop off. Disconnect the plastic tubing fro the Gas Pressure Sensor if the pressure exceeds 130 kpa. 15. The rate of respiration can be easured by exaining the slope of the pressure change vs. tie plot at the right of the screen. Calculate a linear regression for Figure 3 the pressure change vs. tie graph: a. Click on the Pressure Change vs. Tie graph to select it. b. Click the linear Fit button, 0, to perfor a linear regression. A floating box will appear with the forula for a best fit line. c. Record the slope of the line,, in Table 3 as the rate of oxygen consuption by gerinating peas. d. Close the linear regression floating box. 16. Move your data to a stored data run. To do this, choose Store Latest Run fro the Experient enu. Part II Non-gerinating peas, roo teperature 17. Disconnect the plastic tubing connectors fro the rubber stoppers. Reove the rubber stopper fro each test tube. up «p w 18. Repeat Steps 10-16, using test tubes T2 and T3. Part III Gerinating peas, cool teperatures 19. Disconnect the plastic tubing connectors fro the rubber stoppers. Reove the rubber stopper fro each test tube. & 20. Repeat Steps 10-16, using test tubes T1 and T3 in a cold water bath. 21. If instructed by your teacher, ake a printout of the graph with each of the three trials. lie-4 Biology with Coputers

5 Cell Respiration DATA Table 1 Peas Volue (L) Gerinating Non-gerinating Table 2 Water bath Teperature (0C) war cool Table 3 Peas Rate of Respiration (kpa/in) Gerinated, roo teperature Non-gerinated, roo teperature Gerinated, cool teperature QUESTIONS 1. Do you have evidence that cell respiration occurred in peas? Explain. 2. What is the effect of gerination on the rate of cell respiration in peas? 3. What is the effect of teperature on the rate of cell respiration in peas? 4. What was the role of the control respiroeter in each series of experients? 5. Why do gerinating peas undergo cell respiration? EXTENSIONS 1. Copare the respiration rate aong various types of seeds. 2. Copare the respiration rate aong seeds that have gerinated for different tie periods, such as 1, 3, and 5 days. 3. Copare the respiration rate aong various types of sall anials, such as insects or earthwors. Biology with Coputers lie-5