Photosynthesis

1. Photosynthesis Watch this: http://youtu.be/g78utcLQrJ4

2. Chapter 7 Photosynthesis CO 7 Name a plant you have seen recently.

3. Brainstorm... What are some careers or college majors related to plants? U of I - College of Agriculture

4. What is a plant anyway?7.1 Photosynthetic Organisms A. Photosynthesis transforms solar energy B. Organic molecules built by photosynthesis provide both the building blocks and energy for cells.

5. C. Plants use the raw materials: carbon dioxide and water D. Chloroplasts carry out photosynthesis Figure 7.1b

6. E. Chlorophylls and other pigments involved in absorption of solar energy reside within thylakoid membranes of chloroplasts Figure 7.1c

7. Figure 7.2

8. Quick Check - FIVE OR FEWER 1.  Plant 2.  Thylakoid 3.  Photosynthesis 4.  Organic Molecules

9. 7.2 Plants as Solar Energy ConvertersA. Solar Radiation - Only 42% of solar radiation that hits the earth’s atmosphere reaches surface; most is visible light.

10. B. Photosynthetic Pigments - Pigments found in chlorophyll absorb various portions of visible light; absorption spectrum. 1. Two major photosynthetic pigments are chlorophyll a and chlorophyll b.2. Both chlorophylls absorb violet, blue, and red wavelengths best.3.  Most green is reflected back; this is why leaves appear green.

11. 4. Carotenoids are yellow-orange pigments which absorb light in violet, blue, and green regions.5. When chlorophyll breaks down in fall, the yellow-orange pigments in leaves show through.

12. Fall Foliage Slideshow

13. Fall Leaves • Why do leaves turn orange/red/brown in the fall? • What are the major pigments which absorb light? • Why do leaves appear green?

14. D. Photosynthetic Reaction 1. In 1930 C. B. van Niel showed that O2 given off by photosynthesis comes from water and not from CO2.2. The net equation reads:

15. E. Two Sets of Reactions in Photosynthesis1. Light reactions cannot take place unless light is present. They are the energy-capturing reactions.

16. b. Chlorophyl within thylakoid membranes absorbs solar energy and energizes electrons. c. Energized electrons move down the electron transport system; energy is captures and used for ATP production. d. Energized electrons are also taken up by NADP+, becoming NADPH.

17. 2. Calvin Cycle Reactions a. These reactions take place in the stroma; can occur in either the light or the dark. b. These are synthesis reactions that use NADPH and ATP to reduce CO2.

18. What you should know by now.. 1.  The equation for photosynthesis.  Write it! 2.  The structure of a chloroplast.  Sketch it! 3.  Compare the two stages of photosynthesis and their products.  Chart it! **Things are about to get much more difficult**

19. 7.3 The Light Reactions 1.  Two paths operate within the thylakoid membrane                          noncyclic              and                cyclic                           *straight line                       *in a circle 2.  Both paths use ATP, but the noncyclic also produces NADPH (this is where we pick up electrons!) 3.  PHOTOPHOSPHORYLATION = ATP production (phosphorylation means adding a P to ADP  ATP)

20. 1. Light hits photosystem II (yes, II comes before I)and exites an electron in H20 2.  The primary electron acceptor passes the electron down the ETC and generates ATP 3. Light is required for PSI, but not water, it generates NADPH

21. Something trivial....Photosystem I and Photosystem II are named based on when they were discovered, PSI was established first.

22. We use these electrons to go to the Calvin Cycle Figure 7.5 We’ve used our electrons here to form ATP

23. Indicate which system  (PS1 or PS2 or BOTH) ____1.  Splits water ____2.  Produces NADPH____3.  Has an electron transport chain ____4.  Requires light ____5.  Utilizes a primary electron acceptor ____6.  Occurs in the thylakoid ____7.  Requires the input of H20 ____8.  The cyclic path____9.  Uses chlorophyll ____10.  Releases oxygen

24. Are you still confused?    This is pretty hard to visualize, but through the magic of technology, we can watch these processes as animations McGraw Hill Animation Forest Biology - The Light Reactions

25. 7.3   Light Reactions    A.  Two Pathways    B.  Noncyclic    C.  Cyclic    D.   ATP Production  -->  CHEMIOSMOSIS       When H20 is split, two H+ remain            These H+ are pumped from the stroma into the thylakoid             This creates a gradient used to produce ATP from ADP ATP is the whole point of Photosystem II and will be used to power the Light Independent Reactions (Calvin Cycle)

26. Figure 7.7

28. Chemiosmosis is difficult to visualize.So... you get to color it! Yay!  coloring!

29. The Calvin Cycle   Also called *The Light Independent Reactions *The Dark Reactions *Named after Melvin Calvin, who used a radioactive isotope of carbon to trace the reactions.

30. The Calvin Cycle is a series of reactions producing carbohydrates.carbon dioxide fixation, carbon dioxide reduction, and regeneration of RuBP. FIXATIONREDUCTIONREGENERATION

31. B. Fixation of Carbon Dioxide 1. CO2 fixation is the attachment of CO2 to an organic compound called RuBP. 2. RuBP (ribulose bisphosphate) is a five-carbon molecule that combines with carbon dioxide.

32. 3. The enzyme RuBP carboxylase (rubisco) speeds this reaction; this enzyme comprises 20–50% of the protein content of chloroplasts, probably since it is a slow enzyme. Calvin Cycle Animation

33. 1. With reduction of carbon dioxide, a PGA  (3-phosphoglycerate [C3]) molecule forms. C. Reduction of Carbon Dioxide

34. D. Regeneration of RuBP 1. Every three turns of Calvin cycle, five molecules of PGAL are used to re-form three molecules of RuBP. 2. Every three turns of Calvin cycle, there is net gain of one PGAL molecule; five PGAL regenerate three molecules of RuBP.

35. Figure 7.8

36. E. The Importance of the Calvin Cycle 1. PGAL, the product of the Calvin Cycle can be converted into all sorts of other molecules. 2. Glucose phosphate is one result of PGAL metabolism; it is a common energy molecule.

37. Figure 7.9

38. Factors the Affect Photosynthesis 1. Light Quality (color)2. Light intensity3. Light Period4. Carbon Dioxide Availability5. Water Availability

39. In order for photosynthesis to occur, plants must open tiny pores on their leaves called STOMATA. Opening these pores can lead to loss of water.

40. Alternative Pathways The Calvin Cycle is the MOST Common Pathway for Carbon Fixation. Plant Species that fix Carbon EXCLUSIVELY through the Calvin Cycle are known as C3 PLANTS.  Plants in hot dry environments have a problem with water loss, so they keep their stomata partly closed... this results in CO2  deficit (Used in Calvin Cycle), and the level of O2 RISES                 (as Light reactions Split Water Molecules).

41. C4 plants and CAM (Crassulacean acid metabolism) plants use an alternate pathway to FIX carbon dioxide from the air. Figure 7.10

42. THE CAM PATHWAY - Plants that use the CAM Pathway open their stomata at night and close during the day. At night, CAM Plants take in CO2 and fix into organic compounds. During the day, CO2 is released from these Compounds and enters the Calvin Cycle. Because they have their stomata open only at night, they grow slow. Figure 7.11

43. Quick Practice

44. Quick Practice grana thylakoid stroma O2

45. Light & H2O CO2 ADP Pg 129b NADP ATP NADPH O2 glucose

46. A = photosystem IIB = photosystem I C = H20 D = Electron Transport Chain E = ATP Synthase AB = ATP AC = phospholipids AD = light (energy)