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# Investigation05 en

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### Investigation05 en

1. 1. Biology teacher support material Investigation 5 Designed Lab Metabolism of Yeast in Different Temperatures Research Question: How will the different temperatures (5 C° 26 C° 40 C° and 80 C°)affect the amount of CO2 produced by the reaction of yeast? Hypothesis: If the temperature is increased, the enzymes present in the yeast solution will gain the energy from the heat to overcome the activation energy. Also, the average kinetic energy of yeast and glucose will increase. Therefore, the rate of reaction will be increased and CO2 will be produced more at the higher temperature. Variables: Independent: temperature of yeast solution and glucose solution Dependent: metabolism rate and the amount of CO2 Controlled: room temperature, atmosphere, temperatures of solutions, gas sensor Materials: CO2 Gas Sensor Hot plate Thermometer Four 200ml beakers Three 10ml measuring cylinders Three syringes Eight test tubes Distilled water Ice cube Four thermometers Stop watch Yeast 1% glucose Procedure: 1. Prepare four 200ml beakers with 150ml of distilled water 2. Place two of the beakers on the hot plate, and increase the water temperature until 80 C° and 40 C° 3. Leave the third beaker at the room temperature, and put ice cubes in the fourth beaker to lower the temperature until 5 C° 4. Meanwhile, prepare four sets of 15ml yeast solution and 9ml 1% glucose solution in each different test tube; use measuring cylinders and syringes to measure the amount of each solutions 5. Place each set of 15ml yeast solution and 9ml 1% glucose solution in the beakers with different temperatures, 5 °C, 26 °C (room temperature), 40 °C and 80 °C 6. Wait for l0 minutes to stabilize the temperatures of the yeast and glucose solutions at set temperatures by using thermometer 7. In the meantime, set up the computer and CO2 Gas Sensor to collect the data 8. After 10 minutes, take out yeast and glucose solutions from 5 °C,and pour them in the 250ml gas sampling bottle 9. Stabilize the gas sensor. for 100 seconds, and as soon as two solutions are poured, close the bottle with the gas sensor tube and press start button to collect data© International Baccalaureate Organization 2007
2. 2. Biology teacher support materialInvestigation 5 10. After observing 7 minutes, press stop button to stop collecting the data 11. Repeat steps 8-10 for solutions with different temperatures 12. Record the collected data2 © International Baccalaureate Organization 2007
3. 3. Biology teacher support material Investigation 5 Results: Data Collection: Graph1: The rate of yeast metabolism and the amount of CO2 Yeast Metabolism 4000 3000 CO2 (ppm) 2000 1000 0 50 100 150 200 250 300 350 400 450 500 Time (s) Table 1: The change in the amount of CO2 over time 80°C 40°C 26°C 5°C Time (s) C02 (ppm) Time (s) C02 (ppm) Time (s) C02 (ppm) Time (s) C02 (ppm) 0 1227 0 1214 0 1104 0 1056 20 1202 20 1202 20 1110 20 1056 40 1202 40 1188 40 1104 40 1056 60 1182 60 1163 60 1105 60 1066 80 1075 80 1233 80 1086 80 1160 100 1214 100 1696 100 1220 100 1153 120 1268 120 2011 120 1391 120 1202 140 1299 140 2240 140 1444 140 1250 160 1309 160 2389 160 1527 160 1290 180 1329 180 2502 180 1607 180 1329 200 1339 200 2610 200 1633 200 1369 220 1349 220 2723 220 1761 220 1388 240 1369 240 2841 240 1810 240 1408 260 1368 260 2905 260 1849 260 1427 280 1378 280 2952 280 1878 280 1437 300 1388 300 2997 300 1917 300 1454 320 1398 320 3049 320 1946 320 1466 340 1398 340 3097 340 1976 340 1476 360 1407 360 3147 360 2004 360 1496 380 1417 380 3206 380 2035 380 1506 400 1417 400 3265 400 2055 400 1525 420 1427 420 3334 420 2084 420 1534 440 1436 440 3413 440 2113 440 1547 460 1446 460 3492 460 2142 460 1564 480 1446 480 3539 480 2171 480 1574 *Note: The metabolic reaction starts from 100th second as this period is used to show the stability of the sensor© International Baccalaureate Organization 2007
4. 4. Biology teacher support materialInvestigation 5 Table 2: Total change in the amount of CO2 (100sec to 160 sec) 80°C 40°C 26°C 5°C 232 ppm 1843 ppm 951 ppm 421 ppm Table 3 Initial rate of reaction (100sec to 160sec) Temperature 80°C 40°C 26°C 5°C Calculation 1309 -1214 = 95 2389 -1696 = 693 1527 -1220 = 307 1290 -1153 = 137 CO2 (ppm/min) 95 693 307 137 Before the sample solutions were poured in the 250ml bottle, the CO2 sensor was stabilized for 100 seconds.. After 100 seconds, the sample solutions were poured, as the procedure indicates, the yeast started to metabolize sugars, which was indicated by the use of oxygen (O2); therefore, resulting in the release of carbon dioxide (CO2), The CO2 Gas Sensor measures carbon dioxide gas by monitoring the amount of infrared radiation absorbed by carbon dioxide molecules (Aerobic Respiration). In the experiment, four sets of samples in different temperatures, 5 °C, 26 °C, 40 °C, 80 °C, were prepared, and the result shows that the optimum temperature of yeast for metabolizing sugar (glucose) is 40 °C,. At 7minutes, the concentration of CO2 reached 3538.6 ppm. The yeast was also reactive in the room temperature, 26 °C, with the result of 2l70.87ppm at 7minutes. However, at 5 °C, and 80 °C, the concentration of CO2 stayed low, and barely increased over 7minutes, l573.76ppm and l445.8ppm. Discussion: The result supports the hypothesis, which states that as the temperature increases the metabolism reaction rate of yeast will increase; therefore it will result in a higher carbon dioxide concentration in the bottle. The chemical equation for the yeast metabolism is as follows: C6H1206 + 6 O2 6H20 + 6C02 +Energy Glucose + Oxygen Water + Carbon Dioxide +Energy At the temperature of 40 °C, the amount of CO2 increased immediately after the yeast and the glucose was mixed in the bottle. The rate of reaction was faster than other solutions because at the higher temperature, the activation energy to overcome the activation barrier to initiate the chemical reaction is higher. Hence, the initial rate of reaction, such as 307ppm/min, is the fastest. Also at higher temperature, more energy is converted to the kinetic energy; thus, the average kinetic energy becomes higher. Both yeast and glucose molecules move faster, and collide to each other more frequently at higher average kinetic energy. Therefore, the yeast metabolized sugar in glucose faster at 40 °C, and produced the most amount of l843ppm. Similarly, at the room temperature, the metabolism occurred immediately after both solutions were mixed in the bottle. However, the total amount of carbon dioxide at 7minutes was slightly less than 40 °C, On the other hand, at the lower temperature such as 5 °C, the average kinetic energy is much lower than at 40 °C,. Thus, only the low amount of carbon dioxide was produced because the metabolism barely occurred. The total amount of carbon dioxide was l573.76ppm at 7minutes. However, when the temperature of glucose and yeast was increased to 80°C,, the metabolism reaction hardly occurred. The reason for this result is that even though the glucose solution maintained higher average kinetic energy, most of the yeast in the yeast solution was dead by the temperature at 80 °C,. Hence, the total amount of carbon dioxide produced at 7minutes was l445.8ppm, which is the similar result as 5°C, • The result of this experiment is fairly valid according to the common results from the internet. The optimum temperature of yeast from the experiment could be estimated around 30- 40°C,, and the internet sources state that the optimum temperature is between 20-40°C, (AEM). Therefore, the result of this experiment is reliable. However, there are some sources of errors in the experiment. First of all, there is uncertainty in the use of technology such as CO2 Gas Sensor. While © International Baccalaureate Organization 2007
5. 5. Biology teacher support material Investigation 5 the carbon dioxide in the bottle was stabilized for the first minute, the initial amount of carbon dioxide was different each time. The uncertainty of the Gas Sensor is about ± 150 ppm. Therefore, there is a slight invalidity with the use of Gas Sensor but the result shows reliable numbers, therefore, the error could be reduced by controlling the atmosphere as much as possible. Another source of error is the temperature change of solutions after taking out test tubes from the beakers and poured solutions into the Gas Sensor bottle. When the solution was poured into the bottle, the temperature might have increased or decreased to the room temperature and could have affected to the result. Therefore, the error could be reduced by placing the bottle in the ideal temperature so that the temperature is always controlled. In addition, there are some limitations in this experiment. One of the limitations is that there was only limited number of CO2 Gas Sensor available. Thus, the bottle of CO2 Gas Sensor had to be washed and dried for each samples. Another limitation is the limited time to finish the experiment, thus the experiment could not be repeated to acquire more accurate results. In addition, the maximum amount of CO2 that can be measured by the sensor is 5000ppm, and the respiration of yeast did not reach plateau at the maximum time; therefore, there is clearly mechanical limitation and errors in procedure in this experiment. To reduce the error, the amount of yeast solution and glucose could be reduced to minimize the maximum potential amount of CO2 that can be produced by the respiration. Most significantly, the multiple trials of the experiment should not be ignored in order to gain the validity of the experiment. Conclusion: The samples from 40 C° produced the highest amount of carbon dioxide from the metabolism reaction. However, the optimum temperature for the yeast is limited to 30-40 C° because the yeast dies in the high temperature. Therefore, the result of the experiment supports part of the hypothesis, which states that if the temperature is increased, the average kinetic energy of yeast and glucose will increase, therefore, the rate of reaction will be increased and CO2 will be produced more. Sources: Aerobic Respiration. http://faculty.uca.edu/~march/biol/aer_resp/co2_sensor.htm AEM. http://aem.asm.org/cgi/content/full/69/3/1861© International Baccalaureate Organization 2007 5