1 Investigate Photosynthesis and Cellular Respiration with Algae BeadsA ThINQ! Investigation Inspire your students – tomorrow’s researchers CCTCA 2017 – Calgary, AB
2 Life Science Education – Biotechnology Explorer ConsultantBio-Rad (Canada) Life Science Education – Biotechnology Explorer Consultant Bob Malyk BSc. MEd. Senior Biology Teacher (retired) Ridley College St. Catharines, Ontario ThINQ! about it
3 Today you get to think like a student…ThINQ! about it
4 Workshop Outcomes How can you use immobilized algae cells to demonstrate the capture of CO2 from the environment during photosynthesis and the release of CO2 into the environment during cellular respiration? How can you take quantitative and qualitative measurements of photosynthesis and cellular respiration rates, to illustrate CO2 movement? How can you engage students in an authentic inquiry activity that applies concepts relating to photosynthesis and cellular respiration into one lab?
5 Think About it! How difficult is it for your students to make the connection between photosynthesis and cellular respiration? Develop questions about their relationship?
6 This Photosynthesis & Cellular Respiration Kit helps to bridge the connection!Kit Design: Applicable to Biology (Gen Bio -AP) and Environmental Sciences with a teaching emphasis on inquiry-based experiments. For 32 students. Cost $ Algae Beads: Live algae (Scenedesmus obliquus) are immobilized in alginate as “beads”. The algae can photosynthesize and respire while beaded. Indicator: Colorimetric pH indicator allows for qualitative and quantitative data collection.
7 Algae Beads are AWESOME!Beads are easy for students to handle and move! Algae can be reused for multiple Experiments! Algae beads have a long shelf-life & require minimal prep! Algae beads are easy to dispose!
8 Taxonomy Scenedesmus obliquusThere are 74 taxonomically accepted species of Scenedesmus. Scenedesmus is one of the most common freshwater genera Scenedesmus sp. can exist as unicells; they are also frequently found in coenobia of four or eight cells Scenedesmus obliquus is notable for the non-standard coding of its mitochondrial DNA which may represent an intermediate form in the evolution of green algal mitochondrial DNA Scenedesmus obliquus
9 Setting the Stage for Inquiry: Observations + Background = Question100,000’s of algae cells are encapsulated together into a bead. Each bead is permeable to gases such as CO2 and O2. We have a solution that is CO2 sensitive. The solution changes color in the presence of CO2. CO2 O2
10 Developing Investigation Questions!What questions can we ask about Photosynthesis &/or Cellular Respiration using Algae Beads & the CO2 indicator solution? Their relationship? Think Hypothesize Investigate
11 Let’s Investigate Steps 1-2: Transfer Algae beads to cuvetteSteps 3-5: Wash Algae beads with 1 ml of distilled water (not tap H2O – why?) Step 6: Add 1 ml of CO2 Indicator to Algae beads and cap. Step 7: Set Algae Beads in condition of choice. (light or dark) Step 8: Collect data at 5 minute intervals Step 9: Interpret results after 30 minutes Step 10: Continue to expose Algae beads to separate conditions and discuss results
12 Quick Guide 1. Label one empty cuvette LIGHT, and the other cuvette DARK. Label each cuvette so that it does, not obstruct light reaching the algae beads. 2. Label a transfer pipet ALGAE and convert it into a scoop by Use of scissors to cut a transfer pipet at the 250μl mark and make a diagonal cut to create a scoop-like opening. Use this pipet, which now has an enlarged opening, to transfer 20 algae beads into each of the light and dark cuvettes.
13 Quick Guide 3. Label a new transfer pipet EXCESS and use it to remove and discard the liquid that transferred along with the beads. 4. Label a new transfer pipet WASH and use it to add 1ml of distilled water to each of the cuvettes. Let the algae beads incubate in the water for 5 min. to allow indicator within the bead to wash out.
14 Quick Guide 5. Use the WASH transfer pipet to remove the water from the cuvette. Discard the water into the waste container. 6. Label a new transfer pipet INDICATOR and use it to transfer 1 ml of CO2 indicator to each cuvette. Cap cuvettes tightly.
15 Quick Guide 7. Wrap the cuvette labeled DARK in aluminum foil. Place both the cuvettes labeled LIGHT and DARK on their sides 15–25 cm from the lamp. Ensure that the beads are distributed evenly throughout the cuvette and the clear side of the cuvette faces the light.
16 Quick Guide 8. Collect data starting at time = 0 min. Every 5 min, thoroughly mix the CO2 indicator in the cuvettes and determine the color. This can be done by comparing the color of the CO2 indicator in your cuvette to the provided Indicator Color Guide, or by reading the absorbance at 550 nm in a spectrophotometer (make sure your teacher has zeroed the machine). Be quick about taking this reading and immediately return the cuvettes to the experimental conditions until all time points have been measured. 9. If enough time remains after the last time point, switch the LIGHT and DARK cuvettes. Place the cuvette labeled LIGHT in the dark and the cuvette labeled DARK in the light. Continue to record pH or A550 every 5 min.
17 Cell Respiration and PhotosynthesisAnd now presenting… Bio-Rad presents: Cell Respiration and Photosynthesis
18 Sample Results
19 CO2 Indicator Solution pH indicator: CO2 + H2O H2CO3 HCO3- + H+Predictions? Light > Dark > CO2 + H2O H2CO HCO3- + H+ Photosynthesis Respiration Atmospheric CO2 CO2 in solution Predictions? Light > photosynthesis > CO2 consumption > less H+ > pH increases > purple Dark > cellular respiration > CO2 production > more H+ > pH decreases > yellow
20 Lab Overview Activity (* = Stopping Point) Time requiredWhen performed Equilibrate CO2 Indicator Activate algae & aliquot CO2 indicator 15-20 min 3 days prior to lab 1 day prior to lab Lab Investigation #1 & #2 (Microscopy & PS/CR comparison) 30-50 min Day 1 or First Lab *Store beads up to 2 weeks in refrigerator 10 min After Lab 1 Lab Investigation #3 (Effects of Light Color on PS rate) Day 2 or Second Lab * Lab Investigation #4 (Effects of Light Intensity on PS rate) Day 3 or Third Lab Lab Investigation #5 or #6 (Temperature & Mini Ecosystem) Day 4 or Fourth Lab
21 Extensions: Where can we go from here?For this investigation, you investigated the link between photosynthesis and cellular respiration in algae beads exposed to light and dark. What other environmental variables might affect photosynthesis and cellular respiration?
22 Discussion points to consider!What types of organisms likely live at the bottom of the Gulf where the water is most hypoxic? What cellular processes are affected by decreased oxygen levels? What environmental factors can affect the levels of dissolved oxygen in the Gulf waters?
23 What is inquiry? What did we model?Confirmation Students confirm a principle through an activity in which the results are known in advance (“cookbook” lab) Students investigate a teacher-presented question through a prescribed process Structured Students investigate a teacher-presented question using student-designed/selected procedures Guided Students investigate questions that are student-formulated Open
24 What are the benefits of inquiry?Through inquiry, students: Ask questions Make predictions Design plans to investigate answers to the questions Apply mathematical routines to analyze data Develop and refine testable explanations for observed phenomena Ask new questions for further investigation
25 More questions to consider!Phytoplankton (microscopic algae) are primary producers in the Gulf. What environmental factors sustain their growth? What do they produce in return? What is the connection among the substrates and products of photosynthesis and cellular respiration? Why are phytoplankton the ultimate cause of the Dead Zone in the Gulf of Mexico?
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