2. Biology 10 Photosynthesis

3. 2 Introduction Photosynthesis is… –the process by which plants and some bacteria use chlorophyll, a green pigment, to trap sunlight energy. –The energy is used to synthesize carbohydrates

4. 3 Respiration The process by which living things convert the chemical energy in sugars into the energy used to fuel cellular activities

5. 4 ATP: Adenosine Triphosphate

6. 5 Electron Transfer The transfer of electrons is important in ATP production. Electron carriers –strip a hydrogen proton and its electron from a number of organic compounds Respiration –NAD + (becomes NADH) Photosynthesis –NADP + (becomes NADPH)

7. 6 Electron Transfer Oxidation - Loss of Electrons Reduction - Gain of Electrons LEO the lion goes GER OIL RIG

8. 7 General Equation There are two steps in photosynthesis –Light Dependent Reaction –Light Independent Reaction (Dark Reaction)

9. 8 General Outline Light Dependent Reaction Light Independent Reaction

10. 9 Chlorophyll A green chemical which traps sunlight energy Located in the chloroplast

11. 10 Chloroplast Parts Thylakoid –Disk –Granum = stack of disks –Grana = many stacks –site of light dependent reaction Stroma –gel surrounding the thylakoids –site of light independent reaction

12. 11 Thylakoid Location

13. 12 Pigments White light is composed of all colors –red, orange, yellow, green, blue, indigo, violet Chlorophyll –reflects green light –absorbs blue and red ends of the spectrum chlorophyll a -- blue green chlorophyll b -- green Other pigments absorb light energy from other parts of the spectrum.

14. 13 Absorption Spectrum for Chlorophyll

15. 14 Absorption Spectrum for Chlorophyll

16. 15 More on Pigments Pigments are organized into clusters called PHOTOSYSTEMS The purpose of the pigments is to absorb light energy. Q: What really happens when light is captured? A: Electrons from chlorophyll move to a HIGHER energy level.

17. 16 Light Dependent Reaction

18. 17 Light Dependent Reaction

19. 18 Light Dependent Reaction e - e -

20. 19 Light Dependent Reaction

21. 20 Light Dependent Reaction Preview Occurs on the thylakoid membrane. There are a few key points to understand: –Light is absorbed by a photosystem (excites an electron) –Electrons moves through ETS in a step by step fashion. Lost energy is used to pump H + into the lumen (inside) These H + ’s are used to produce ATP using the CF1 particle –Electrons are delivered to another photosystem. –Light again strikes this photosystem and electrons moves through another ETS –The electrons join up with NADP + and H + to form NADPH –ATP and NADPH go to the light independent reaction in the stroma.

22. 21 Thylakoid Location

23. 22 Light Dependent Reaction

24. 23 Light Dependent Reaction

25. 24 Light Dependent Reaction

26. 25 Light Dependent Reaction

27. 26 Light Dependent Reaction

28. 27 Light Dependent Reaction e - e -

29. 28 Light Dependent Reaction

30. 29 Light Dependent Reaction

31. 30 Light Dependent Reaction

32. 31 Light Dependent Reaction

33. 32 Light Dependent Reaction

34. 33 Light Dependent Reaction e - e -

35. 34 Light Dependent Reaction

36. 35 Light Dependent Reaction

37. 36

38. 37

39. 38

40. 39

41. 40 Light Dependent Reaction

42. 41 Light Dependent Reaction

43. 42 Light Dependent Reaction

44. 43 Light Dependent Reaction

45. 44 What happens to the H + in the Lumen?? Eventually, H + in the lumen will get so packed in that they will want to “leak” out. –diffusion The only spot they can find to get out of the lumen is a special hollow molecule called a CF1 Particle. This leads to the production of ATP

46. 45 Light Dependent Reaction

47. 46 Light Dependent Reaction

48. 47

49. 48 Wait a Minute... If light keeps on striking Photsystem 2, ejecting high energy electrons, won’t the chlorophyll eventually run out of electrons? Yes. Except that the electrons are replaced by using some from … H2OH2O

50. 49 Photolysis Photo = light lysis = break Photolysis = the breaking of a water molecule using light energy. –Occurs in the lumen of the thylakoid.

51. 50 Photolysis

52. Light Dependant Reaction Review Flash animation Photosynthesis 2 Photosynthesis Photophosphorylation

53. 52 Practice Using the thylakoid blank handout, label photons, electrons, NADP, H +, NADPH, ADP, P, ATP, CF1, photolysis, proton pump, photsystems 1 &2, thylakoid membrane, stroma, lumen...

54. Now... The Light Independent Reaction