What is the chemical formula for photosynthesis?

1. What is the chemical formula for photosynthesis? • What are the two main steps involved and where do they occur? • How do the reactants of photosynthesis enter the plant cell? • Agenda: • Chloroplast Structure • Photosynthesis and Pigments • Chromatography Lab • Homework: • 1. Finish reading Chp. 10

2. 6 CO2 + 6 H20 + light  C6H1206 + 6 02

3. Chapter 10 Photosynthesis CO 7 • Photosynthesis converts light energy to the chemical energy of food. • Organic molecules built by photosynthesis provide both the building blocks and energy for cells. • Autotrophs vs. Hetertrophs vs. Chemotrophs • Occurs in the chloroplasts • Chlorophylls and other pigments involved in absorption of solar energy reside within thylakoid membranes of chloroplasts

5. 6 CO2 + 6 H20 + light  C6H1206 + 6 02

6. 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.

7. 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. Very little green light is absorbed; most is reflected back; this is why leaves appear green.

8. 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.

9. C. Absorption and action spectrum - A spectrophotometer measures the amount of light that passes through a sample of pigments.1) As different wavelengths are passed through, some are absorbed.2) Graph of percent of light absorbed at each wavelength is absorption spectrum • .

10. 3) Photosynthesis produces oxygen; production of oxygen is used to measure the rate of photosynthesis. 4) Oxygen production and, therefore, photosynthetic activity is measured for plants under each specific wavelength; plotted on a graph, this produces an action spectrum. 5) Since the action spectrum resembles absorption spectrum, this indicates that chlorophylls contribute to photosynthesis.

12. Write a short paragraph (4-5 sentences) explaining the steps of photosynthesis. Make sure to include where in the plant cell the steps are occurring and what the beginning and end products are of each stage.

13. What does the visible light wavelength spectrum have to do with photosynthesis? What color of light is least effective in driving photosynthesis? Explain. Is photosynthesis and endergonic or exergonic reaction? Explain.

14. Explore Which wavelengths of light are most effective in driving photosynthesis? Students will get into groups of 3 and read Engelmann’s experiment in which he attempted to answer the above question. What if Englemann had placed a red-colored filter between the prism and the alga? How would the results have differed?

15. 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:

16. What you should know by now.. • The equation for photosynthesis 2.  The structure of a chloroplast 3.  Which spectrum(s) of light is used by plants and the pigments associated with light spectrum. 4.  The two stages of photosynthesis and their products **Things are about to get much more difficult**

17. 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 3.  PHOTOPHOSPHORYLATION = ATP production

18. 1. Light hits photosystem II and exites an electron, 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

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

20. 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

21. 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

22. 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)

23. Figure 7.7

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

25. Chemiosmosis Video/Animations Animation of Photosynthesis, Chemiosmosis (ATP Synthesis)

26. 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.

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

28. 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.

29. 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

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

31. 2. Each of two PGA molecules undergoes reduction to PGAL in two steps. 3. Light-dependent reactions provide NADPH (electrons) and ATP (energy) to reduce PGA to PGAL.

32. 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.

33. Figure 7.8

34. 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.

35. Exit Slip In the light reactions, what is the initial electron donor? Where do the electrons end up? To synthesize one glucose molecule, the Calvin cycle uses ____ molecules of CO2, ____ molecules of ATP, and ____ molecules of NADPH. Homework: Finish reading Chp. 10. Make sure to pay attention to the unit objectives.

36. Figure 7.9

37. 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.

38. C4 plants C3 plants and CAM plants use an alternate pathway to FIX carbon dioxide from the air. Figure 7.10

39. Figure 7.11

40. Quick Practice

41. Quick Practice grana thylakoid stroma O2

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

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