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Quiz

Quiz. Which lab did you like? Why? (25pts) Which lab did you learn the most from? (25pts) Which lab did you not like? Why? (25pts) How do you think the labs could be improved? (25pts). How?. Why?. Photosynthesis & e - transport. Pathway thinking. What is DCPIP?. What are its uses

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Quiz

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  1. Quiz Which lab did you like? Why? (25pts) Which lab did you learn the most from? (25pts) Which lab did you not like? Why? (25pts) How do you think the labs could be improved? (25pts)

  2. How? Why? Photosynthesis &e- transport • Pathway thinking

  3. What is DCPIP? • What are its uses • What does it ‘indicate’

  4. X1 X2 Following the Scientific Approach: Predicting

  5. The experiment’s afoot! • Hypothesis I: The herbicide (‘X’) acts before DCPIP has a chance to nab the electron • Hypothesis II: The herbicide (‘X’) acts after DCPIP has a chance to nab the electron

  6. NO reduction of DCPIP (stays blue) X1 If we get this result, are we ready to publish a conclusion?

  7. X2 • Rampant reduction of DCPIP (turns clear) If we get this result, are we ready to publish a conclusion?

  8. Technical Aspects 1 • What do you want? • Round 1 – KEEP the LIQUID • Round 2 – KEEP the CHUNK • Part B • Step 9 – three minutes • Step 11 – five minutes • **DON’T change the speed on the centrifuge • MAKE THE CHANGE* • Page 13-10, STEP 6: target absorbance should be 0.1 instead of 0.2 specified in the manual

  9. Corrections Continued • PART C, STEP 6 • Adjust the concentration of your chloroplast solution so that it would have an absorbance of 0.1, not 0.2 • Ask me if you still have questions about how to do this after reading the lab manual carefully

  10. Technical Aspects 2 • How long do you let it go? • At what point in time will the chloroplast-induced reduction have taken place, but the random reduction not yet have occurred at significant levels? • How often do you need to measure the absorbance? • When will you start measuring the absorbance? • How will you know you can stop making measurements?

  11. Technical Aspects 3 • What does herbicide ‘need’ to ‘do its thing’? • What’s happening to DCPIP sitting in the tube prior to the experiment starting? • What happens to results if tubes are not thoroughly mixed? • Is there a difference between 600 & 660 nm? Should you pay attention to which the protocol calls for when? • If you have a tube that’s supposed to be ‘dark’, where should it be most/all of the time?

  12. LASTLY Your chloroplast preparation Dilute into ACETONE 3 2 Read at 660 1 4 Apply your calculated dilution to the preparation (dilute using BUFFER, not acetone!!!) Your experimental material! Compare reading to 0.1 Dilute the original material by the ratio (actual reading/0.1)

  13. DO NOT DO YOUR EXPERIMENT IN ACETONE!!! (that is only for the dilution calculation)

  14. More reminders… • DO NOT DO YOUR EXPERIMENT IN ACETONE!!! (that is only for the dilution calculation) • Measure the absorbance of the acetone + chloroplast solution at 660 nm (only use the spec that are marked with a post-it for that) • Measure the absorbance for the rest of your experiment at 600 nm (any spec. in the room will work for that)

  15. Thinking thoughts • Why is acetone used? • Why do you think the stock chloroplast solution must be diluted? • Why is the chlorophyll concentration an important factor?

  16. More thoughts • Where should your tubes be relative to the lights? • Should you allow your contents to settle to the bottom of the tube? • Is it advantageous to have the tubes vertical this week?

  17. Homework • Whence the herbicide conclusions? • Description of tube contents, purposes, model for events therein (per the rubric)

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