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Photosynthesis

Photosynthesis. Introduction. 6 CO 2 + 6 H 2 O + light energy → C 6 H 12 O 6 + 6 O 2 Photosynthesis consists of two independent pathways called the light-dependent reaction (light reaction) and the light-independent reaction (dark reaction). Introduction.

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Photosynthesis

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  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).

  3. 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.

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

  5. Structure of a Chloroplast

  6. Electromagnetic Spectrum

  7. Why are plants green?

  8. 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.

  9. Structure of Chlorophyll

  10. 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.

  11. Light Reaction

  12. 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)

  13. Photosystems

  14. Excited Electrons

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

  16. ATP Synthase

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

  18. Step 1

  19. Step 2

  20. Step 3

  21. Step 3

  22. Step 3

  23. Step 3

  24. Step 3

  25. Step 3

  26. ~ e low high Step 4

  27. Step 4

  28. Step 4

  29. Step 4

  30. Step 4

  31. Step 4

  32. Step 5

  33. Step 5

  34. Step 5

  35. Step 5

  36. Step 5

  37. NADP+ NADPH + H+ Step 5

  38. high low Step 6

  39. Step 6

  40. Step 6

  41. Step 6

  42. Step 6

  43. ADP + P ~ e Chemiosmosis ATP Step 6

  44. NADP+ ADP + P Reactants

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

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