Transcript
Pre-Lab Questions Why is cellular respiration necessary for living organisms? Cellular respiration is necessary for living because it’s the process where glucose is converted into usable energy. Why is fermentation less effective than respiration? The reason that fermentation is less effective than respiration is because it does not completely break down glucose molecules. What is the purpose of glycolysis? Provide pyruvate for the trichloroacetic acid cycle by turned glucose into pyruvate, so it can enter into the Krebs cycle to produce more energy. How many ATP molecules are produced in aerobic respiration? How many ATP molecules are produced during fermentation and glycolysis? Ideally, aerobic respiration will produce 38 ATP molecules. When glucose undergoes fermentation there is a net gain of 2 ATP molecules. Experiment 1: Fermentation by Yeast Data Tables Table 1: Yeast Fermentation Data Tube Initial Gas Height (mm) Final Gas Height (mm) Net Change 1 7 8.5 1.5 2 7 9 2 3 5 5 0 4 4 4 0 5 5 6 1 Post-Lab Questions Include your hypothesis from Step 1 here. Be sure to include at least one piece of scientific reasoning in your hypothesis to support your predictions. I believe that fermentation will result from the production of carbon dioxide, which will cause an increase in the final gas height. Did you notice a difference in the rate of respiration between the various sugars? Did the artificial sugar provide a good starting material for fermentation? Yes, I did notice a difference; the artificial sugars did not provide good starting material for fermentation. We can conclude this because, there was no change in the height of gas. Was anaerobic fermentation occurring? How do you know (use scientific reasoning)? Yes, anaerobic respiration did occur. We know this because there is an increase of height in the gas column., showing us that aerobic fermentation is occurring because of the production of carbon dioxide. If you observed respiration, identify the gas that was produced. Suggest two methods you could use for positively identifying this gas. I believe that the gas produced was carbon dioxide, you can infer this because of the bubble formation and the change in height of the gas column. Hypothesize why some of the sugar or sweetener solutions were not metabolized, while others were. Research the chemical formula of Equal® and Splenda® and explain how it would affect yeast respiration. I believe that the enzyme theobromine was the reason that the sugars stopped from metabolizing. I believe that equal is unable to be metabolized, and Splenda is metabolized in the gut. How do the results of this experiment relate to the role yeast plays in baking? Fermentation in yeast produces ethanol and CO2; CO2 allows the bread to rise. What would you expect to see if the yeast cell metabolism slowed down? How could this be done? Heat speeds up the process of metabolism while the cold slows it down. Indicate sources of error and suggest improvements (for example, what types of controls could be added?). You could add temperature as a control group to this experiment to ensure that the surroundings have been the same. Experiment 2: Aerobic Respiration in Beans Data Tables Table 2: Bromothymol Blue Color Change Over Time for Pinto Beans Time Pre-Soaked Pinto Beans Dry Pinto Beans No Pinto Beans 0 min Blue Blue Blue 30 min Blue-Green Blue Blue 60 min Green Blue Blue 90 min Bright Green Blue Blue 120 min Bright Green Blue Blue 150 min Light Green Blue Blue 180 min Yellow Green Blue Blue 24 hours Yellow Blue Blue Table 3: Bromothymol Blue Color Change Over Time for Kidney Time Pre-Soaked Kidney Beans Dry Kidney Beans No Kidney Beans 0 min Blue Blue Blue 30 min Blue Green Blue Blue 60 min Green Blue Blue 90 min Bright Green Blue Blue 120 min Bright green Blue Blue 150 min Light Green Blue Blue 180 min Yellow Green Blue Blue 24 hours Yellow Blue Blue Post-Lab Questions How did the color of the bromothymol blue solution in each beaker change over time in each condition? For the beakers that contain no beans or unsoaked beans, the solution remained blue. In the beaker containing soaked kidney beans the solution turns from blue to green, from green to yellow. What is the mechanism driving the bromothymol blue solution color change? In the case of the soaked kidney beans, carbon dioxide is released into the water turning it into a weak acid, creating a color change in the bromothymol. What can be inferred from the color change of the bromothymol blue solution? The bromothymol solution changes color when there is an acid present in the beaker. In this case the only beaker to change colors was the one with soaked kidney beans. From this, we can infer that cellular respiration has occurred in beaker with soaked kidney beans. What evidence do you have to support that cellular respiration occurred in the beans? Explain your answer. We can identify that cellular respiration has occurred in the soaked kidney bean beaker. CO2 was released during respiration in the water containing the soaked beans, creating a reaction form carbonic acid. The bromothymol’s blue color reacted with the acid and changed its color from blue-to-green-to-yellow over time. What are the controls in this experiment, and what variables do they eliminate? Why is it important to have a control for this experiment? The control group in this experiment would be the beaker with dry beans, and the one with no beans. It is always important to have a control group in your experiment because we can tell the differences between the changes in reaction. In this case, it’s important to be able to see the release of CO2 to be able to tell if respiration has occurred. If this experiment were conducted at 0 °C, what difference would you see in the rate of respiration? Why? At 0 o C respiration would happen at an extremely slow rate, because low or cold temperatures inhibit respiration. The release of CO2, and the change of color would vastly be slower compared to the room temperature that the experiment was performed. Would you expect to find CO2 in your breath? Why? Yes, we breathe out carbon dioxide as a product of cellular respiration and the foods we eat. Carbs, fats, and proteins are transformed into glucose which then gives energy to our cells. What else could you incorporate into this experiment to verify that the gas is responsible for the color change? Design an experiment that shows the steps required. For this experiment we can actually look back at question 6, the temperature. A change in temperature could be used during this experiment to verify that the gas is responsible o the color change, and not any other outside forces.
