Respiration and Photosynthesis Lab | My Assignment Tutor

Name: _______________________________________ Section Number: ____________Lab Partners: _______________________________________________________________________________Respiration and Photosynthesis LabPre-labRead through the handout, and do the prelab quiz on D2L.Safety NoteBe very gentle with animal specimens. These will be used for all labs this week, and some will be kept andreused for other courses this semester.Post-lab Clean UpPlace animal organisms and germinating seeds back on cart. Plant leaves and aluminum foil can be disposed ofin the trash. Turn off LabQuests, and remove CO2 probes. Put all items neatly back on cart ready for the nextclass to use.LabPurpose Use a carbon dioxide (CO2) gas sensor to monitor carbon dioxide concentrations Know the equation for aerobic respiration Demonstrate carbon dioxide production during respiration Know the equation for photosynthesis Demonstrate carbon dioxide uptake during photosynthesis Define the following terms: aerobic respiration, photosynthesis, electron transport system,chemoheterotroph, photoautotrophOverviewAll organisms need energy to drive metabolism in order to live. Most eukaryotic organisms do this strictlythrough aerobic respiration. Aerobic respiration is the breakdown of organic molecules (often sugars) in thepresence of oxygen to release energy and capture it in the form of ATP. The ATP produced can then be used torun anabolic pathways and other cellular functions necessary for the survival and reproduction of the organism.FIGURE 1 CELL RESPIRATION FORMULA1The complete breakdown of glucose involves multiple pathways, each with several steps. Through thesepathways, electrons originating from glucose are passed to various molecules, releasing energy with theirpassage. Oxygen acts as the final electron acceptor in aerobic respiration, forming water by acquiring theelectrons. The carbons from the glucose ultimately end up in CO2, which is released as a waste product.FIGURE 2 AEROBIC RESPIRATIONPhotosynthesis is another important metabolic pathway of some cells. Like respiration, photosynthesis uses anelectron transport chain to synthesize ATP and reduce electron carriers. Unlike respiration, these energymolecules are used to synthesize organic compounds, such as glucose.FIGURE 3 PHOTOSYNTHESIS FORMULAPhotosynthesis is a metabolic pathway that consists of two phases, each consisting of several steps. The firstphase is the “photo” phase, or the light reactions. During the light reactions, chlorophyll pigments absorb lightenergy, which excites electrons to an energy level above the ground state. If an electron is excited to a highenough level, it is expelled from the chlorophyll molecule and delivered to electron carriers along an electrontransport chain in the thylakoid membrane of chloroplasts. As the electrons are passed down the chain, protonsare pumped from one side of the membrane to another, creating a proton gradient. These protons then movedown their gradient, through ATP synthase located in the membrane, which drives the formation of ATP.Electrons moving down the electron transport chain in the light reactions ultimately are accepted by NADP+ tobecome NADPH, which is then able to take the electrons elsewhere to use them to do work.FIGURE 4 PHOTOSYNTHESIS2The second phase of photosynthesis is the “synthesis” phase or the light-independent reactions. The lightindependent reactions use the ATP and NADPH formed in the light reactions to fix carbon into organiccompounds. Specifically, glyceraldehyde-3-phosphate is formed, which is then converted into glucose, starch, orother biological molecules. The molecules can be used to form cell structures, do catalytic activity, or behydrolyzed to produce ATP for endergonic reactions.Animals and plants will be used in this experiment to study aerobic respiration and photosynthesis. You willdetermine how light affects the respiration and photosynthesis rates of these organisms by monitoring CO2production over time.There is a direct relationship between respiration rate and CO2 produced. There is a similar relationship betweenrate of photosynthesis and CO2 consumed. Rate is an occurrence per unit of time. A familiar rate is velocity,measured in miles/hour. In this experiment,Respiration Rate=CO2( ppm)time(s)where ppm = parts per million, s = seconds. For instance, the more glucose broken down in a five-minute timeperiod, the greater the rate of CO2 released.In the procedure today, you will be looking for the production of CO2 through respiration or the uptake of CO2through photosynthesis. We will compare metabolic activity in various animals and plants, both in the light andin the dark. Production or uptake of CO2 will be determined by measuring CO2 using a gas chamber, a CO2 gassensor, and the LabQuest2 monitor.Hypothesis and PredictionBefore you begin the experiment, read through the procedure, and develop a clear hypothesis to explain therelationship between type of metabolism and type of organism. Generate specific predictions from yourhypothesis, including predictions for what will happen in the light vs. dark for each organism.Record your hypothesis (explanation or why) and predictions (what you think the specific results will be) in theResults section of your lab report.Materials per group of 3-4 students An animal (choose from: millipede, earthworm, 5-10 cockroaches, 5-10 mealworm larvae, 5-10mealworm adults) A green plant (freshly plucked leaf, spinach leaf) 5-10 geminating seeds 600 mL beaker 2 Weigh boats LabQuest 2 CO2 probe Respiration chamber (#6 rubber stopper) Piece of aluminum foil large enough to completely cover a chamber with probe insertedMaterials to share as class Electronic balance3 Flood lights Large beakers filled with water as heat sinksProcedureProduction of CO2 during aerobic respirationObservation of the uptake of CO2 during photosynthesisThese procedures will be run using the exact same set-ups as each other, except one set will be run in light, andone run in the dark. We will compare these results to determine if respiration or photosynthesis is occurring.Set up Equipment Before the Experiment:1. Plug in CO2 probe to LabQuest2. Insert the probe into the opening of the plastic respiration chamber. The Lab Quest shouldautomatically detect that the CO2 probe has been connected.3. Allow 90 seconds for warm up.4. Insert the pointer from the Lab Quest into the calibration hole on the side of the CO2 probe until the redlight blinks. The concentration of CO2 will appear on the display screen of the Lab Quest. Allow 30 seconds for the reading to stabilize. The probe reading should stabilize to about 380 ppm.Determine Mass of Organisms5. Weigh an empty 500 mL covered beaker. Record this in Table 1 in the Results section.6. Obtain one type of any of the following organisms: 1 millipede, 1 earthworm, 5-10 cockroaches, 5-10mealworm larvae, 5-10 mealworm adults. Each group should choose a different organism. Place theorganisms in the 500 mL beaker.7. Weigh the organisms in the 500 mL covered beaker. Record in Table 1.8. Determine the mass of the organisms without the beaker. Record their mass in grams (g) in the table.9. Select a green leaf organism, such as spinach or philodendron. You may weigh these in a weigh boatrather than a beaker since it is unlikely the plants will crawl away. Record the mass in grams in the table.10. Weigh 5-10 germinating seeds in a weigh boat. Record mass in the table.11. Transfer masses for each type of organism to Table 3 in the Results section.Determine Rate of Metabolism12. Carefully remove the probe from the respiration chamber, and transfer the animals to the chamber.13. Reinsert the probe. Be sure probe is placed snugly in the chamber opening, and all other openings areclosed. (If the chamber you are using has two openings, a #6 rubber stopper may be used to close thenon-screw cap end).414. Press “Play,” or the green triangle on the LabQuest screen to begin data collection.15. Collect data for 3 minutes. You should see a linear graph plotted on the Lab Quest’s screen of CO2 (ppm)vs. Time (sec).16. At the end of 3 minutes, press “Stop” or the red square on the screen.17. Take the probe out of the chamber and fan fresh air into the chamber to make sure animals do notsuffocate (not necessary for the plant specimens).18. Use the pointer to select either the entire screen or part of the graph that is the most linear. To selectonly a portion of the graph, use the green pointer to click and drag a section of the graph on the screen.19. After selecting a linear portion of the graph you can find the slope of the line (which representsrespiration rate) by following the below sequence: Press: Analyze Curve Fit CO2 Select “Linear” from pull down menu OK/EnterWhere y = mx + b is the general equation for linear curves, m is the slope with units of ppm/sec. Apositive slope indicates that CO2 has been produced, and a negative slope indicates that CO2 has beenconsumed. Record the slope, including the sign, in the column titled Slope 1 of Table 2 in the Resultssection.20. Repeat steps 13-18, to get 2-3 repetitions of the data. Record the slopes in columns titled Slope 2 andSlope 3, respectively of Table 2. Calculate the average for each set of conditions, and record in the lastcolumn of Table 2, and transfer the same values to column 3 (Average Slope) in Table 3. The conditionsto be tested are (if all are available): Animal in light Animal in dark Green plant in light Green plant in dark Germinating seeds in light Germinating seeds in darkDark conditions should be performed by wrapping the respiration chamber in aluminum foil during datacollection. Light conditions should be performed under the full light of the room which can be enhancedusing flood lights. If flood lights are used, they get quite hot. A larger beaker filled with water should beplaced between the flood light and the organism to prevent overheating (and killing) the organism. Ithas also helped to let the leaves sit under the flood light for 1-3 minutes before beginning the readings.21. OPTIONAL: Save your data on a USB drive for all samples (if available) Insert USB drive into LabQuest Select FILE > Export > select USB symbol at topo Name sample being export (example: mealworm/light, group 1)o Press OK5o Remove USB drive and repeat for remaining sampleso Share data with all members of group22. In order to standardize the respiration rate per unit of mass, divide the slope of the line by the mass ofthe animal or seeds. The units are ppm/sec/g, which is a measure of the concentration of CO2 producedper second per gram of animal or seed. Record this value in Table 3.23. Graph the results of average respiration rates for all samples. Be sure to include a descriptive title andproper axes labels.When you are done collecting data, place animal organisms and germinating seeds back on cart. Plant leavesand aluminum foil can be disposed of in the trash. Turn off LabQuests, and remove CO2 probes. Put all itemsneatly back in kit trays and on cart ready for the next class to use. Wipe down benches before you leave.The remaining pages contain the results sections and conclusion questions that are to be submitted.6Name: ____________________________________________________________________ Section: __________Lab Partner(s): _______________________________________________________________________________Respiration and Photosynthesis Lab ReportUse the Overview and Procedures sections above to help you complete the questions below. Makesure to answer the questions fully. Scan or take pictures of the following pages once completed andcreate a PDF file. Submit the PDF to the assignment folder on D2L by the due date.Hypothesis and PredictionBefore you begin the experiment, read through the procedure, and develop a clear hypothesis toexplain the relationship between type of metabolism and type of organism. Generate specificpredictions from your hypothesis, including predictions for what will happen in the light vs. dark foreach organism.Hypothesis (explanation or why):Prediction (what you think the specific results will be):ResultsTABLE 1: MASS OF ORGANISM Organism NameMass Of Beaker/Boat (g)Mass Of Beaker/Boat +Organism (g)Mass Of Organism (g)1234 7TABLE 2: CO2 LEVELS OVER TIME ChamberConditionSlope 1 (ppm/sec)Slope 2 (ppm/sec)Slope 3 (ppm/sec)Average Slope (ppm/sec)1Animal in light2Animal in dark3Plant in light4Plant in dark5Seeds in light6Seeds in dark78 TABLE 3: CALCULATION OF RESPIRATION RATES OF ORGANISMS OrganismsMass of organism (g)Average slope (ppm/sec)Average Respiration rate(ppm/sec/g)Animal in lightAnimal in darkPlant in lightPlant in darkSeeds in lightSeeds in dark Conclusions1. What are the products of respiration?2. What are the reactants of photosynthesis?3. What changes in CO2, if any, do you expect to see in each chamber?8A. Animal in lightB. Animal in darkC. Green plant in lightD. Green plant in darkE. Germinating seeds in lightF. Germinating seeds in dark4. Your calculated respiration rates should have either positive or negative signs, depending on thedifferent conditions tested. Describe what a positive or negative sign indicates: respiration orphotosynthesis, and why this is the case for each.5. Which chamber(s) show respiration?6. Which chamber(s) show photosynthesis?7. Does cellular respiration occur simultaneously with photosynthesis in plants? How could you determinethe relative rates of each, using the data from today’s lab?8. Why is it important to calculate the respiration rate per mass of organism, rather than just comparingoverall CO2 changes between each organism?910


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