Photosynthesis…life’s basic Rx!

1. Photosynthesis…life’s basic Rx! • Basic questions • Some history • Some plant anatomy • Some biochemistry light reactions dark reactions photolysis

2. Basic questions?? • What do plants eat? • Why do plants need light? • Why do plants need water? • Why are plants green?

3. Some History…Greeks to …? • “what do plants eat”? • VanHelmont’s tree… • Priestly & phlogiston… • Lavoisier lost his head over some O2…well? • Englemann & bacteria? • Melvin Calvin 1948!

4. Summary of photosynthesis ??? • CO2, H2O and light go in… • Carbohydrate and O2 come out • 6CO2+6H2O • C6H12O6+O2

5. Anatomy of a leaf • Function(s)?? • Collect sunlight • Make ‘food’ • Move food to storage • Thus… • Structure related to function…

6. WHY ARE LEAVES GREEN??? ENLARGE

15. Summary of the chloroplast • Double membranes • Thylakoid disks called grana (chlorophyll) • Stroma • ETS • ‘loose’ enzymes

16. 2 sets of photosynthetic reactions • Light dependent • Light energy captured • 3 reactions • Light independent • Calvin cycle • Makes pyruvate (C3)

17. What is light? • What are photons? • Energy & photons

19. What is chlorophyll? • Plant pigment • Imbedded in membrane of thylakoid disks • Why green?

20. What colors are absorbed? • What colors reflected?

22. QUIZ • Why are leaves green? • Relate chloroplast to mitochondria • What is chlorophyll? • What cell organelle contains chlorophyll?

23. How is light ‘captured’? • How to ‘grab’ a photon? • How to ‘hold onto’ the ‘hot potato’ (energy of photon)

25. Quiz • What are the ‘ units’ of light? • What colors are ‘captured’? • How are photons ‘captured’?

26. 3 light dependent reactions • Photosystem I…cyclic photophosphorylation • Photosystem II…noncyclic photophosphorylation • photolysis

27. The Light Reactions (light dependent) • Cyclic Photo-phosphorylation (photosystem I) • Noncyclic Photo-phosphorylation (photosystem II) • Photolysis

28. Cyclic photophosphorylation

29. Cyclic photophosphorylation • Photon ‘excites’ e- • e- ‘absorbed’ • e- passed thru ETS • ATP generated via chemiosmosis • e- ‘recycled’

32. photosystem I

33. What’s produced in photo I? How is ATP made? What happens to the electron? ATP Chemiosmosis recycled Quiz

34. Noncyclic photophosporylation • NADH • Oxygen • ATP (chemiosmosis) • Electron IS NOT recycled

35. photolysis photosystem II

37. What is made? How is ATP made? What is the importance of O2? ATP, NADPH, O2 Chemisosmosis Free oxygen released thus changing the world…why?? Quiz: photosystem II + photolysis

38. Products of light reactions • ATP (via chemiosmosis) • NADPH • Oxygen • What happens to these? And… • What about night?

40. What happens during ‘dark’ Rx (light independent reactions) • CO2 from air is ‘fixed’… • ATP & NADPH carry energy from light Rx • C3…pyruvate (PGA) is formed • 2X ‘turns’=C6…? • C6>organic ‘stuff’

41. The Calvin-Benson Cycle • How to store ATP? • Why reinvent the wheel? • Long-term storage?

42. ribulose bisphosphate carboyxlase

44. Calvin cycle

45. Quiz-Dark reactions (Calvin cycle) • Why are these reactions called ‘dark’ • What are the products of the Calvin cycle? • Where in the chloroplast do these Rx occur? • What kinds of molecules can be made from PGAL (pyruvate)? • What is the most prevalent protein on the planet? Why is it so important?

46. Alternative pathways?? • Why is the former called C3pathway? • photorespiration…? • C4… • CAM • Not as efficient as C3 but, hey….beats nothing?

49. Photosynthesis summary

50. Energy flow in nature