The Effects of Cell Respiration on Bromothymol Blue By: Ethan Howard R.Matthews Introduction: This lab explains how cell respiration works using an indicator called Bromothymol blue. All living things undergo a process called Cell Respiration. This process occurs when food molecules are broken down into smaller particles. A main part of this process is that animals and humans take in oxygen and release carbon dioxide by breathing, which is easy to observe. The one thing different about breathing is that plants do not breathe like us animals do, so respiration in plants is not as easily observable as in animals. The equation that keeps animals and plants alive is Cell Respiration. The equation for this life dependent process for animals is, “ C6H12O6 + O2 → CO2 + H2O.” which is this the opposite of equation for plants in photosynthesis which is, “ 6CO2 + 6H2O → C6H12O6 + 6O2.” Purpose: The purpose of this investigation was to demonstrate that humans release carbon dioxide and to determine if plants release carbon dioxide as a product of respiration. Materials: The materials used for this lab are: Bromothymol blue 400mL beaker from the small test tubes Disposable pipet Parafilm® wax 4 Small test tubes Forceps 1 Straw disposed immediately after use. Cotton ball 10 rye seedlings obtained from the teacher Aluminum foil Labeling tape and pen Lab Safety: The safety rules that apply to this lab include: 1­7,13,15,20 Procedure: These are the steps to completing this lab: 1: Labeling tape is supplied to label the test tubes A, B, C, and D. 2: A pipetful of Bromothymol blue indicator is placed into each of the labeled test tubes (A, B, C, and D) and gently returned to the beaker. The beaker is served a test tube rack. 3: A straw is used to gently exhale carbon dioxide into test tube B. If the lab partners doing this step is anxious not to inhale any of the indicator solution, the teacher should be called over to do this step for the lab partners. The color of the indicator solution is recorded before 20 minutes. The test tubes are then returned to the beaker. 4: A small piece of cotton is placed into test tube C using the forceps provided. 10 seedlings are placed inserted on top of the cotton using the forceps again. Test tube C is covered with aluminum foil so light is not shinned into it. 5: All the test tubes are sealed using a piece of Parafilm® wax. 6: Test tube D is completely covered with aluminum foil after the color of the solution is recorded. 7: The color of the indicator solution is recorded in the “before” column of the data table. 8: After 24 hours have passed, the color change of the indicator solution is recorded onto the “after” column of the data table. 9: The Analysis Questions are answered and a formal lab write­up is completed. Results Table/Calculations Table: TEST TUBE Description of the Contents of the Test Tube Color of Bromothymol Indicator Solution ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
­­­ Before 20 minutes Color of Bromothymol Indicator Solution ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
­­­ After 20 minutes A B. blue blue blue B B. blue + exhale yellow green C B. blue + cotton + seeds blue yellow D B. blue + cotton blue blue The “Before” and “After” images can be found at the end of the lab report. Discussion: A. The report results addresses questions 1­5: 1: What is the purpose of using bromothymol solution? The purpose of using bromothymol solution is so that the presence of cell respiration could be indicated using a liquid color change. 2: Did the color of the indicator change after CO2 was exhaled into the test tube? The color of the indicator changed after CO2 was exhaled because it underwent cell respiration. 3: Did the color of the indicator change in the test tube that contained the seedlings? The color of the indicator changed in the test tube that contained seedings because the seedlings underwent cell respiration therefore changing the color of the indicator solution. 4: Compare the reaction that occured in the test tube that contained the seedlings with the one which was exhaled. Are they similar? Why or why not? The test tube that contained the seedlings and the test tube that was exhaled are very similar in the reaction because they were the only test tubes that have a color change in the Bromothymol blue. Therefore the seeds and exhaling made cell respiration occur. 5: Did cell respiration occur in this experiment? In which test tubes? How can you tell? Cell respiration occured in this experiment in test tube B and C. I can tell because these were the only test tubes that had a color change while test tube A and D stayed they same color, which is blue. B. Seedlings vs. adult plants addresses to questions 6­7. Interpreted data and report trends using actual data as evidence. 6: Why do you suppose seedlings were used in this experiment rather than adult plants? Using common sense, i suppose seedlings were used in this experiment rather than adult plants because the seedlings are small enough to fit into the small test tube, while adult plants are to big to fit. 7: How would your results have been affected if you had used more seedlings? Fewer seedlings? If more seedlings were used, than cell respiration would occur faster, but if fewer seedlings were used, than cell respiration would occur slower. The data received were color changes in the test tubes. Some of them changed color, while other did not. The reason why some had cell respiration occuring is because of exhaling CO2 or a form of plants, like what happened in test tubes B and C. The reason why some test tubes had no cell respiration occuring and no color change is because they did not contain something needed for cell respiration such as in test tube A, when only Bromothymol blue was added, and nothing else to made it undergo cell respiration or have a color change. In test tube D only Bromothymol blue and cotton was added. As observed, nothing changed in test tube D, so therefore, cotton did not change the indicators color or undergo cell respiration. C. The Cell Respiration summary addresses to questions 8­9: 8: Why is the process of cellular respiration common to all forms of life? The process of cellular respiration is common to all forms of life because it is how cells make waste. 9: Describe the 3 stages of cellular respiration. The first stage is called Glycolysis. This stage starts off with a glucose molecole of C6. It is broken into 2NADH + 4ATP + 2 pyrubic acids of C3 each by the means of inputing 2ATP. This gives a net of 2ATP. The second stage is called the Krebs Cycle. This stage continues on from the first stage where the 2 pyrubic acids both lose 1 carbon atom and those 2 carbon atoms are released as carbon dioxide as waste. Now that the pyrubic acids are broken into C2 each, they are called Acetate(2C). NADH than picks up the 2 acetate molecules and carries them to the mitochodrion. The acetate molecules are to big to get into the gates of the mitochondrion, so they break themselves apart into carbon dioxide in order to fit. Once their inside, they attach to C4 molecules called Oxaloacetic acid and those molecules break into C2 each. This cycle just happens again and again. The third stage is called the Electron Transport Chain (ETC). This stage transports H+ around cell membrane from the liquid part of the mitochondrion called the matrix into the cell membrane of the mitochondrion therefore making 38 ATP. D: The relation between autotrophs and heterotrophs addresses question 10: 10: Why do we need plants? Why do plants need animals? Describe the relationship between cellular respiration and photosynthesis. We need plants because they make oxygen for us to breathe. Plants need animals to make carbon dioxide for plants to breathe. The relationship between cellular respiration and photosynthesis is that cell respiration is the process of making waste, and photosynthesis is the process of making oxygen for animals to breathe and making carbon dioxide from animals so plants can breathe. E: Error sources and description of how errors will impact data: An error source in the lab could be if the seedlings were put into the test tube with carbon dioxide exhaled into the Bromothymol blue. This error would impact data because a wrong color change might occur and wrong results will be recorded. An error source could be if seedlings were not added to the test tube with cotton inside (test tube C). This error would impact data because if seedlings were not added to test tube C, than the color would not change and cellular respiration will not occur. Conclusion: The purpose of this investigation was to determine the effects of Cellular respiration on Bromothymol blue. The results suggests that cellular respiration occurs in plants and CO2. Works Cited: Ravgiala, R (2008) Cell Respiration Notesheet. Tyngsborough, MA: Tyngsborough School District.