1. Photosynthesis

2. Photosynthesis Photosynthesis is the way that plants make food from sunlight –You take in food which is digested and then transferred to cells for use by mitochondria –Plants can’t “eat” so they make food which is then transferred to the mitochondria –Mitochondria then transform the “food energy” into chemical energy

3. Photosynthesis Why does it matter? –Source of nearly all the energy on Earth –Process by which atmospheric gases are maintained in the ratios we need to survive

4. Photosynthesis Who photosynthesizes? Some bacteria

5. Photosynthesis Who photosynthesizes? Some bacteria Some protists

6. Photosynthesis Most plants

7. Photosynthesis Heterotroph: organism that must consume food Autotroph: organism that makes its own food (photosynthesis)

8. Photosynthesis 6 CO 2 + 6 H 2 O + light energy → C 6 H 12 O 6 + 6 O 2 Carbon dioxide WaterCarbohydrate Oxygen

9. Photosynthesis 6 CO 2 + 6 H 2 O + light energy → C 6 H 12 O 6 + 6 O 2 Carbon dioxide WaterCarbohydrate Oxygen

10. Vein Epidermis Mesophyll Guard cells Vein Stoma Epidermis

11. Photosynthesis Vein: water delivery

12. Photosynthesis Epidermis: water-proof covering of the surface of the leaf –Prevents unwanted loss of water and gases

13. Photosynthesis Stoma: Opening in the leaves –water exits –O 2 exits –CO 2 enters

14. Photosynthesis Stoma: Opening in the leaves –water exits –O 2 exits –CO 2 enters Transpiration

15. Photosynthesis Guard cells: surround stoma –Open and close stoma

16. Photosynthesis Mesophyll: central layer of cells –contains chloroplast-rich cells –site where most photosynthesis occurs

17. Photosynthesis

18. Photosynthesis 2 sets of reactions:

19. Photosynthesis –LIGHT DEPENDENT REACTIONS

20. Photosynthesis

21. Photosynthesis 2 sets of reactions: –LIGHT DEPENDENT REACTIONS –LIGHT INDEPENDENT REACTIONS (Calvin cycle)

22. Photosynthesis

23. Light Dependent Reactions

24. Thylakoids contain pigments

25. Light Dependent Reactions Pigments: molecules that absorb light energy

26. Light Dependent Reactions Pigments: molecules that absorb light energy –Electrons are energized by absorbing energy and “jumping” energy levels

27. Light Dependent Reactions Pigments: molecules that absorb light energy –Electrons are energized by absorbing energy and “jumping” energy levels –A specific amount of energy is required in order for the electron of a specific atom to jump and land in another energy level Ex. Long jumping versus hopscotch

28. Light Dependent Reactions Thylakoids contain the pigment chlorophyll –Chlorophylls a and b Absorb light on opposite ends of the visible light spectrum Between 500 and 600 nm light is reflected Why chlorophyll appears green

29. Light Dependent Reactions Thylakoids contain the pigment chlorophyll Absorbed Reflected

30. Light Dependent Reactions Thylakoids contain pigments called carotenoids –Absorb light below 550 nm –Appear red, orange, and yellow

31. Light Dependent Reactions Thylakoids contain pigments called carotenoids AbsorbedReflected

32. Light Dependent Reactions Thylakoids contain pigments –Which pigment is dominant in deciduous trees right now?

33. Light Dependent Reactions Pigment in the thylakoids form Photosystems –Network of pigments held together within a protein matrix –Channel energy absorbed from light to a specific pigment molecule: reaction center chlorophyll

34. Light Dependent Reactions Pigment in the thylakoids form Photosystems –Reaction center chlorophyll passes the energy (via an energized electron) to a primary electron acceptor: Ferredoxin

35. Light Dependent Reactions Process of replacing the electrons that follows this step depends on the organism: –Bacteria: cyclic –Algae and plants: non-cyclic

36. Light Dependent Reactions Cyclic phosphorylation –Bacteria –Contain only 1 photosystem: Photosystem I –From electron acceptor, electrons go through electron transport system from which ATP is produced –Electrons then return to Photosystem I

37. Light Dependent Reactions Non-cyclic phosphorylation –Algae and plants –Contain 2 photosystems: Photosystem I, and Photosystem II –PS II acts first

38. Light Dependent Reactions Non-cyclic phosphorylation –Photon of light energy excites electron which is passed from PS II to electron transport chain and then to PS I –Another photon of light re-excites the electron now in PS I which passes the electron to the primary electron acceptor and through a series of reactions

39. Light Dependent Reactions Non-cyclic phosphorylation –Electrons lost from PS II must be replaced PS II takes an electron from protein Z Protein Z then takes an electron from water by splitting a water molecule into H + ions and O H + ions are used later, O forms O 2 and is “exhaled”

40. Light Dependent Reactions Electron transport chains –Series of enzymes embedded in membrane called the cytochrome complex –Receive excited electrons from PS II and PS I –Electrons are passed from 1 molecule to the next

41. Light Dependent Reactions Electron transport chains –Energy from the electrons energized in PS II powers a proton pump –Proton pump pumps protons into the thylakoid space –Results in high concentration of protons in the thylakoid space –Concentration gradient powers ATPase

42. Light Dependent Reactions Electron transport chains –ATPase allows protons back out of membrane –Rush of protons provides enough energy to attach a phosphate to an ADP forming –This process is called chemiosmosis ATP

43. Light Dependent Reactions Electron transport chains –Energy from the electrons energized in PS I is passed to a reduction complex –At the reduction complex NAD + is transformed into NADH

44. Light Dependent Reactions Electron transport chains –NAD + is an electron acceptor: it holds on to the energy from the electrons until it can be used to bind a phosphate group to an ADP

45. Light Dependent Reactions Electron transport chains – and NADH produced leave the thylakoid to participate in the next set of reactions: the light independent reactions or Calvin cycle ATP

46. Light Dependent Reactions Ferredoxin

47. Light Dependent Reactions Ferredoxin Z

48. Light Dependent Reactions Ferredoxin Energy is taken from the electrons and is used to make ATP from ADP Z

49. Light Dependent Reactions Feredoxin Ferredoxin Energy is taken from the electrons and is used to make ATP from ADP Z

50. Light Dependent Reactions Ferredoxin Energy is taken from the electrons and is used to make ATP from ADP Energy is taken from the electrons and is used to make NADPH from NADP Z

51. Light Dependent Reactions Ferredoxin Energy is taken from the electrons and is used to make ATP from ADP Energy is taken from the electrons and is used to make NADPH from NADP ATP and NADPH leave the thylakoid and enter the stroma where they are used in the Calvin cycle Z

52. Light Dependent Reactions Light 2e - Ferredoxin Water molecule is split by protein Z H2OH2O O 2H + + 2e - Photosystem II Electron Transport System Energy is removed from the electrons as they move down the ETC. The energy is used to pump p + into thylakoid. p + s power ATPase which converts ADP to ATP ADP + P i + Energy → ATP 2e - Ferredoxin Electron Transport System NADPH + H + 2e - NADP + + 2H + Light ATP and NADPH leave thylakoid and enter stroma to be used in the Calvin cycle Oxygen is released as a by-product Z Cytochrome complex NADPH reductase Photosystem I

53. Light Independent Reactions (Calvin cycle)

54. Calvin cycle Uses ATP and NADPH produced in the light-dependent reactions Also uses CO 2 taken in through stoma Requires no sunlight Produces carbohydrate which is used by mitochondria in respiration

55. Calvin cycle (3 PGA) (From light dependent reactions)

56. Calvin cycle (3 PGA) (From light dependent reactions) (From light dependent reactions)

57. Calvin cycle (PGA) (From light dependent reactions) (From light dependent reactions) (From light dependent reactions)

58. Calvin cycle RuBP CO 2 Rubisco 3 PGA ATP NADPH ADP NADP + PiPi G3P Output for use by mitochondria in respiration G3P (carbohydrate) G3P ATP ADP 1,3 Bisphosphoglycerate CARBON FIXATION REDUCTION REGENERATION OF RuBP

59. Calvin cycle 3 CO 2 + 3 RuBP → 6 PGA

60. Calvin cycle 3 CO 2 + 3 RuBP → 6 PGA ↓ Rubisco

61. Calvin cycle 3 CO 2 + 3 RuBP → 6 PGA → → 6 G3P ↓ Rubisco

62. Calvin cycle 3 CO 2 + 3 RuBP → 6 PGA → → 6 G3P ↓ Rubisco ↓ 6 ATP

63. Calvin cycle 3 CO 2 + 3 RuBP → 6 PGA → → 6 G3P ↓ Rubisco ↓ 6 ATP ↓ 6 NADPH

64. Calvin cycle 3 CO 2 + 3 RuBP → 6 PGA → → 6 G3P ↓ Rubisco ↓ 6 ATP ↓ 6 NADPH output ↓

65. Calvin cycle 3 CO 2 + 3 RuBP → 6 PGA → → 6 G3P → 3 RuBP ↓ Rubisco ↓ 6 ATP ↓ 6 NADPH output ↓

66. Calvin cycle 3 CO 2 + 3 RuBP → 6 PGA → → 6 G3P → 3 RuBP ↓ Rubisco ↓ 6 ATP ↓ 6 NADPH output ↓ ↓ ATP

67. Calvin cycle 3 CO 2 + 3 RuBP → 6 PGA → → 6 G3P → 3 RuBP ↓ Rubisco ↓ 6 ATP ↓ 6 NADPH output ↓ ↓ ATP

68. Calvin cycle 3 CO 2 + 3 RuBP → 6 PGA

69. Photosynthesis

70. Calvin cycle