1. LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick Photosynthesis Chapter 10

2. Figure 10.1 Photosynthesis is the process that converts solar energy into chemical energy. Directly or indirectly, photosynthesis nourishes almost the entire living world Autotrophs are organisms that harvest their own energy (almost always by photosynthesis).

3. (a) Plants (b)Multicellular alga (c)Unicellular protists (d) Cyanobacteria (e)Purple sulfur bacteria 10  m 1  m 40  m Figure 10.2 Fossil Fuels

4. Chloroplasts: The Sites of Photosynthesis in Plants Any green part of a plant can do photosynthesis, but most of it happens in the leaves. The green color is from chlorophyll, the green pigment within chloroplasts. Chloroplasts are found mainly in cells of the mesophyll, the interior tissue of the leaf. © 2011 Pearson Education, Inc.

5. Figure 10.4 Mesophyll Leaf cross section Chloroplasts Vein Stomata Chloroplast Mesophyll cell CO 2 O2O2 20  m Outer membrane Intermembrane space Inner membrane 1  m Thylakoid space Thylakoid Granum Stroma CO 2 enters and O 2 exits the leaf through microscopic pores called stomata. The chlorophyll is in the membranes of thylakoids (connected sacs in the chloroplast); thylakoids may be stacked in columns called grana. Chloroplasts also contain stroma, a dense interior fluid.

6. Tracking Atoms Through Photosynthesis Photosynthesis is a complex series of reactions that can be summarized as the following equation: Chloroplasts split H 2 O into hydrogen and oxygen –incorporating the electrons of hydrogen into sugar molecules –and releasing oxygen as a by-product 6 CO 2 + 12 H 2 O + Light energy  C 6 H 12 O 6 + 6 O 2 + 6 H 2 O © 2011 Pearson Education, Inc.

7. Figure 10.5 Reactants: Products: 6 CO 2 6 H 2 O 6 O 2 12 H 2 O C 6 H 12 O 6

8. Photosynthesis as a Redox Process Photosynthesis reverses the direction of electron flow compared to respiration. Photosynthesis is a redox process in which H 2 O is oxidized and CO 2 is reduced. Photosynthesis is an endergonic process; the energy boost is provided by light. © 2011 Pearson Education, Inc.

9. Figure 10.UN01 Energy  6 CO 2  6 H 2 O C 6 H 12 O 6  6 O 2 becomes reduced becomes oxidized

10. The Two Stages of Photosynthesis light reactions (the photo part) Calvin cycle (the synthesis part) © 2011 Pearson Education, Inc.

11. The light reactions (in the thylakoids) –Split H 2 O –Release O 2 –Reduce NADP + to NADPH –Generate ATP from ADP by photophosphorylation © 2011 Pearson Education, Inc.

12. The Calvin cycle (in the stroma) forms sugar from CO 2, using ATP and NADPH. The Calvin cycle begins with carbon fixation, incorporating CO 2 into organic molecules. © 2011 Pearson Education, Inc.

13. Light Light Reactions Chloroplast NADP  ADP + P i H2OH2O Figure 10.6-1

14. Light Light Reactions Chloroplast ATP NADPH NADP  ADP + P i H2OH2O O2O2 Figure 10.6-2

15. Light Light Reactions Calvin Cycle Chloroplast ATP NADPH NADP  ADP + P i H2OH2O CO 2 O2O2 Figure 10.6-3

16. Light Light Reactions Calvin Cycle Chloroplast [CH 2 O] (sugar) ATP NADPH NADP  ADP + P i H2OH2O CO 2 O2O2 Figure 10.6-4

17. Key Points from Sections 10.2 and 10.3 Light Reactions: –visible light –wavelength –electron excitation –photosystems Calvin Cycle: –carbon fixation –RuBP –G3P

18. Figure 10.7 Gamma rays X-rays UV Infrared Micro- waves Radio waves Visible light Shorter wavelength Longer wavelength Lower energy Higher energy 380 450500 550600650 700 750 nm 10 5 nm 10 3 nm 1 nm 10 3 nm 10 6 nm (10 9 nm) 10 3 m 1 m electromagnetic spectrum

19. Chloroplast Light Reflected light Absorbed light Transmitted light Granum Figure 10.8 Pigments are substances that absorb visible light. Different pigments absorb different wavelengths.

20. (b) Action spectrum (a) Absorption spectra Engelmann’s experiment (c) Chloro- phyll a Chlorophyll b Carotenoids Wavelength of light (nm) Absorption of light by chloroplast pigments Rate of photosynthesis (measured by O 2 release) Aerobic bacteria Filament of alga 400 500600700 400 500600700 400 500600700 RESULTS Figure 10.10 Chlorophyll a Accessory pigments: chlorophyll b carotenoids

21. Excitation of Chlorophyll by Light When a pigment absorbs light, an electron goes from a ground state to an excited state, which is unstable © 2011 Pearson Education, Inc.

22. Excited state Heat ee Photon (fluorescence) Ground state Photon Chlorophyll molecule Energy of electron (a) Excitation of isolated chlorophyll molecule (b) Fluorescence Figure 10.12 When a pigment absorbs light, it goes from a ground state to an excited state, which is unstable.

23. Figure 10.13 (b) Structure of photosystem II (a) How a photosystem harvests light Thylakoid membrane Photon Photosystem STROMA Light- harvesting complexes Reaction- center complex Primary electron acceptor Transfer of energy Special pair of chlorophyll a molecules Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID) Chlorophyll STROMA Protein subunits THYLAKOID SPACE ee

24. Figure 10.13a (a) How a photosystem harvests light Thylakoid membrane Photon Photosystem STROMA Light- harvesting complexes Reaction- center complex Primary electron acceptor Transfer of energy Special pair of chlorophyll a molecules Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID) ee

25. Figure 10.13b (b) Structure of photosystem II Thylakoid membrane Chlorophyll STROMA Protein subunits THYLAKOID SPACE

26. Figure 10.14-1 Primary acceptor P680 Light Pigment molecules Photosystem II (PS II ) 1 2 ee

27. Figure 10.14-2 Primary acceptor H2OH2O O2O2 2 H  + 1/21/2 P680 Light Pigment molecules Photosystem II (PS II ) 1 23 ee ee ee

28. Figure 10.14-3 Cytochrome complex Primary acceptor H2OH2O O2O2 2 H  + 1/21/2 P680 Light Pigment molecules Photosystem II (PS II ) Pq Pc ATP 1 235 Electron transport chain ee ee ee 4

29. Figure 10.14-4 Cytochrome complex Primary acceptor H2OH2O O2O2 2 H  + 1/21/2 P680 Light Pigment molecules Photosystem II (PS II ) Photosystem I (PS I ) Pq Pc ATP 1 235 6 Electron transport chain P700 Light ee ee 4 ee ee

30. Figure 10.14-5 Cytochrome complex Primary acceptor H2OH2O O2O2 2 H  + 1/21/2 P680 Light Pigment molecules Photosystem II (PS II ) Photosystem I (PS I ) Pq Pc ATP 1 235 6 7 8 Electron transport chain P700 Light + H  NADP  NADPH NADP  reductase Fd ee ee ee ee 4 ee ee

31. Photosystem II Photosystem I Mill makes ATP ATP NADPH ee ee ee ee ee ee ee Photon Figure 10.15

32. Cyclic Electron Flow Cyclic electron flow uses only photosystem I and produces ATP, but not NADPH No oxygen is released Cyclic electron flow generates surplus ATP, satisfying the higher demand in the Calvin cycle © 2011 Pearson Education, Inc.

33. Figure 10.16 Photosystem I Primary acceptor Cytochrome complex Fd Pc ATP Primary acceptor Pq Fd NADPH NADP  reductase NADP  + H  Photosystem II Cyclic Electron Flow (the “fermentation” of photosynthesis)

34. Mitochondrion Chloroplast MITOCHONDRION STRUCTURE CHLOROPLAST STRUCTURE Intermembrane space Inner membrane Matrix Thylakoid space Thylakoid membrane Stroma Electron transport chain HH Diffusion ATP synthase HH ADP  P i KeyHigher [H  ] Lower [H  ] ATP Figure 10.17

35. Figure 10.18 STROMA (low H  concentration) THYLAKOID SPACE (high H  concentration) Light Photosystem II Cytochrome complex Photosystem I Light NADP  reductase NADP  + H  To Calvin Cycle ATP synthase Thylakoid membrane 2 13 NADPH Fd Pc Pq 4 H + +2 H + H+H+ ADP + P i ATP 1/21/2 H2OH2O O2O2

36. Carbon enters the cycle as CO 2 and leaves as a sugar named glyceraldehyde 3-phospate (G3P) For net synthesis of 1 G3P, the cycle must take place three times, fixing 3 molecules of CO 2 The Calvin cycle has three phases –Carbon fixation (catalyzed by rubisco) –Reduction –Regeneration of the CO 2 acceptor (RuBP) © 2011 Pearson Education, Inc. Concept 10.3: The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO 2 to sugar

37. Input 3 (Entering one at a time) CO 2 Phase 1: Carbon fixation Rubisco 3PP P6 Short-lived intermediate 3-Phosphoglycerate 3P P Ribulose bisphosphate (RuBP) Figure 10.19-1

38. Input 3 (Entering one at a time) CO 2 Phase 1: Carbon fixation Rubisco 3PP P6 Short-lived intermediate 3-Phosphoglycerate 6 6 ADP ATP 6PP 1,3-Bisphosphoglycerate Calvin Cycle 6 NADPH 6 NADP  6 P i6 P i 6P Phase 2: Reduction Glyceraldehyde 3-phosphate (G3P) 3P P Ribulose bisphosphate (RuBP) 1P G3P (a sugar) Output Glucose and other organic compounds Figure 10.19-2

39. Input 3 (Entering one at a time) CO 2 Phase 1: Carbon fixation Rubisco 3PP P6 Short-lived intermediate 3-Phosphoglycerate 6 6 ADP ATP 6PP 1,3-Bisphosphoglycerate Calvin Cycle 6 NADPH 6 NADP  6 P i6 P i 6P Phase 2: Reduction Glyceraldehyde 3-phosphate (G3P) P 5 G3P ATP 3 ADP Phase 3: Regeneration of the CO 2 acceptor (RuBP) 3P P Ribulose bisphosphate (RuBP) 1P G3P (a sugar) Output Glucose and other organic compounds 3 Figure 10.19-3

40. The Importance of Photosynthesis: A Review Light energy  chemical energy Sugar made in the chloroplasts  chemical energy (for cellular respiration) and carbon building blocks (for cells structures) Plants store excess sugar as starch in structures such as roots, tubers, seeds, and fruits. © 2011 Pearson Education, Inc.

41. Light Light Reactions: Photosystem II Electron transport chain Photosystem I Electron transport chain NADP  ADP + P i RuBP ATP NADPH 3-Phosphoglycerate Calvin Cycle G3P Starch (storage) Sucrose (export) Chloroplast H2OH2O CO 2 O2O2 Figure 10.22

42. Review Questions 1.What do the terms wavelength, visible spectrum, and photon mean? 2.What happens when an electron gets excited? 3.What is the difference between the two photosystems? 4.What is cyclic electron flow and when does it happen? 5.What is carbon fixation? 6.What are RuBP and G3P and how are they produced? 7.Compare and contrast cellular respiration and photosynthesis (at least 3 ways).