1. Photosynthesis

2. Introduction 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
Photosynthesis consists of two independent pathways called the light-dependent reaction (light reaction) and the light-independent reaction (dark reaction).

4. Introduction
Light Reactions: the energy in sunlight is trapped, O2 is released, and both ATP and NADPH + H+ (hydrogen-carrier molecule) are formed
Dark Reactions: the ATP and NADPH + H+ react with CO2 from the atmosphere and form glucose
The entire process results in the transformation of light energy from the sun into energy stored in the bonds of the glucose molecule.

6. Structure of a Chloroplast
The light reactions take place in the thylakoid membrane
The dark reactions take place in the stroma

7. Structure of a Chloroplast

10. Electromagnetic Spectrum

11. Why are plants green?

12. Pigments Pigments are light-absorbing compounds.
Pigments appear colored because they absorb light of certain wavelengths and reflect that of others.
Chlorophyll a is the primary pigment in green plants that absorbs red and blue/violet light and reflects green light.

13. Structure of Chlorophyll

14. Accessory Pigments
Chloroplasts also contain other pigments called accessory pigments.
Accessory pigments trap wavelengths of light that cannot be absorbed by chlorophyll a and then transfer the energy to chlorophyll a molecules for use in photosynthesis. In this way, accessory pigments enable plants to use a greater amount of the sun’s energy than is available to chlorophyll alone.

17. Light Reaction

18. Light Reaction Also called Light Dependent Reaction
Pigments that are in the chloroplasts intercept light and begin the light reactions of photosynthesis.
The light reactions occur in two photosystems (located in the thylakoid membrane):
Photosystem: a unit of several hundred chlorophyll a molecules and associated acceptor molecules
-photosystem I (PSI)
-photosystem II (PSII)

19. Photosystems

20. Excited Electrons

21. NADPH
NADP+ is an electron acceptor
NADP+ + 2 e- + 2 H NADPH + H+

22. ATP Synthase

23. Primary Electron Acceptor ETC Proton Pump Thylakoid Lumen ATP Synthase
PSI
PSII
Thylakoid
Lumen
Water (H2O)
Oxygen (O2)
Hydrogen Ion (H+)
Electron
ATP Synthase

24. Step 1

25. Step 2

26. Step 3

27. Step 3

28. Step 3

29. Step 3

30. Step 3

31. Step 3

32. ~ e
low
high
Step 4

33. Step 4

34. Step 4

35. Step 4

36. Step 4

37. Step 4

38. Step 5

39. Step 5

40. Step 5

41. Step 5

42. Step 5

43. NADP+
NADPH
+ H+
Step 5

44. high
low
Step 6

45. Step 6

46. Step 6

47. Step 6

48. Step 6

49. ADP + P ~ e
Chemiosmosis
ATP
Step 6

50. NADP+
ADP + P
Reactants

51. O2 is
released
into the
atmosphere
NADPH
+ H+ DR
ATP
Products

53. Dark Reaction

54. Dark Reaction
The dark reaction is also known as the Calvin Cycle, after an American scientist (Melvin Calvin) who figured out the pathway.
The dark reaction is also known as the C3 Cycle because the first stable products of this pathway are molecules that contain three carbon atoms.
The Calvin Cycle occurs in the stroma.

55. ~ ~ 6 CO2 unstable compound 6 RuBP 6 ATP 12 PGA e 12 ATP 6 ADP + P e
10 PGAL
12 ADP + P
Glucose C
12 PGAL C
12 NADPH + H+ e-
2 PGAL C
12 NADP+

58. The following slides are
ONLY for Level I!

59. The C4 Cycle

60. C4
vs.
CAM

61. Hint for Level I Test Short Answer Question

62. The End!