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. Overview: The Process That Feeds the Biosphere _______________is the process that converts solar energy into chemical energy Directly or indirectly, photosynthesis __________ almost the entire living world © 2011 Pearson Education, Inc.

3. ______________ sustain themselves without eating anything derived from other organisms Autotrophs are the producers of the biosphere, producing ____________________ from CO 2 and other inorganic molecules Almost all plants are ____________________, using the energy of sunlight to make organic molecules © 2011 Pearson Education, Inc.

4. Photosynthesis occurs in __________________, certain other __________, and some __________ These organisms feed not only themselves but also most of the living world © 2011 Pearson Education, Inc.

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

6. ________________ obtain their organic material from other organisms Heterotrophs are the _________________ of the biosphere Almost all heterotrophs, including humans, depend on photoautotrophs for _____________ © 2011 Pearson Education, Inc.

7. The Earth’s supply of ________________ was formed from the remains of organisms that died hundreds of millions of years ago In a sense, fossil fuels represent stores of __________________ from the distant past © 2011 Pearson Education, Inc.

8. Concept 10.1: Photosynthesis converts light energy to the chemical energy of food ____________________ are structurally similar to and likely evolved from photosynthetic bacteria The ___________________________ of these cells allows for the chemical reactions of photosynthesis © 2011 Pearson Education, Inc.

9. Chloroplasts: The Sites of Photosynthesis in Plants __________________ are the major locations of photosynthesis Their green color is from _________________, the green pigment within chloroplasts Chloroplasts are found mainly in cells of the _______________, the interior tissue of the leaf Each mesophyll cell contains ____________ chloroplasts © 2011 Pearson Education, Inc.

10. CO 2 enters and O 2 exits the leaf through microscopic pores called _________________ The chlorophyll is in the membranes of _______________ (connected sacs in the chloroplast); thylakoids may be stacked in columns called grana Chloroplasts also contain ____________, a dense interior fluid © 2011 Pearson Education, Inc.

11. Mesophyll Leaf cross section Chloroplasts Vein Stomata Chloroplast Mesophyll cell CO 2 O2O2 20  m Figure 10.4a

12. Outer membrane Intermembrane space Inner membrane 1  m Thylakoid space Thylakoid Granum Stroma Chloroplast Figure 10.4b

13. Tracking Atoms Through Photosynthesis: Scientific Inquiry Photosynthesis is a complex series of reactions that can be summarized as the following equation: ___________________________________________ © 2011 Pearson Education, Inc.

14. The Splitting of Water Chloroplasts split ________ into hydrogen and oxygen, incorporating the electrons of hydrogen into ______________ molecules and releasing ______________ as a by-product © 2011 Pearson Education, Inc.

15. 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

16. Photosynthesis as a Redox Process Photosynthesis ________________ the direction of electron flow compared to respiration Photosynthesis is a redox process in which ______ is oxidized and __________ is reduced Photosynthesis is an ______________ process; the energy boost is provided by light © 2011 Pearson Education, Inc.

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

18. The Two Stages of Photosynthesis: A Preview Photosynthesis consists of the ______________ (the photo part) and ________________ (the synthesis part) The light reactions (in the thylakoids) –____________________ –Release __________ –Reduce ___________ to NADPH –Generate ATP from ADP by _______________________________ © 2011 Pearson Education, Inc.

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

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

21. Concept 10.2: The light reactions convert solar energy to the chemical energy of ATP and NADPH ______________ are solar-powered chemical factories Their thylakoids transform light energy into the chemical energy of _________ and __________ © 2011 Pearson Education, Inc.

22. The Nature of Sunlight Light is a form of electromagnetic energy, also called _________________________________ Like other electromagnetic energy, light travels in rhythmic _______________ ________________ is the distance between crests of waves _________________ determines the type of electromagnetic energy © 2011 Pearson Education, Inc.

23. The _____________________ is the entire range of electromagnetic energy, or radiation ________________________ consists of wavelengths (including those that drive photosynthesis) that produce colors we can see Light also behaves as though it consists of discrete particles, called ___________________ © 2011 Pearson Education, Inc.

24. 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

25. Photosynthetic Pigments: The Light Receptors ________________are substances that absorb visible light Different pigments absorb different __________ Wavelengths that are not absorbed are _____________ or _________________ Leaves appear green because chlorophyll ______________ and ______________ green light © 2011 Pearson Education, Inc.

26. Chloroplast Light Reflected light Absorbed light Transmitted light Granum Figure 10.8

27. A _____________________ measures a pigment’s ability to absorb various wavelengths This machine sends light through pigments and measures the fraction of light _____________ at each wavelength © 2011 Pearson Education, Inc.

28. Figure 10.9 White light Refracting prism Chlorophyll solution Photoelectric tube Galvanometer Slit moves to pass light of selected wavelength. Green light High transmittance (low absorption): Chlorophyll absorbs very little green light. Blue light Low transmittance (high absorption): Chlorophyll absorbs most blue light. TECHNIQUE

29. An _____________________ is a graph plotting a pigment’s light absorption versus wavelength The absorption spectrum of _______________ suggests that violet-blue and red light work best for photosynthesis An ____________________ profiles the relative effectiveness of different wavelengths of radiation in driving a process © 2011 Pearson Education, Inc.

30. (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

31. The action spectrum of photosynthesis was first demonstrated in 1883 by Theodor W. _______________ In his experiment, he exposed different segments of a filamentous alga to different wavelengths Areas receiving wavelengths favorable to photosynthesis produced excess _______ He used the growth of aerobic bacteria clustered along the alga as a measure of O 2 production © 2011 Pearson Education, Inc.

32. _________________ is the main photosynthetic pigment Accessory pigments, such as ______________, broaden the spectrum used for photosynthesis Accessory pigments called _______________ absorb excessive light that would damage chlorophyll © 2011 Pearson Education, Inc.

33. Figure 10.11 Hydrocarbon tail (H atoms not shown) Porphyrin ring CH 3 CH 3 in chlorophyll a CHO in chlorophyll b

34. Excitation of Chlorophyll by Light When a pigment absorbs light, it goes from a ____________ state to an _____________ state, which is unstable When excited electrons fall back to the ground state, photons are given off, an afterglow called ____________________ If illuminated, an isolated solution of chlorophyll will fluoresce, giving off _________________ © 2011 Pearson Education, Inc.

35. Figure 10.12 Excited state Heat ee Photon (fluorescence) Ground state Photon Chlorophyll molecule Energy of electron (a) Excitation of isolated chlorophyll molecule (b) Fluorescence

36. A Photosystem: A Reaction-Center Complex Associated with Light-Harvesting Complexes A ________________ consists of a ______________ _______________ (a type of protein complex) surrounded by light-harvesting complexes The ___________________________ (pigment molecules bound to proteins) transfer the energy of photons to the reaction center © 2011 Pearson Education, Inc.

37. 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

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

39. A _____________________________ in the reaction center accepts excited electrons and is reduced as a result Solar-powered transfer of an electron from a _____________________ molecule to the _________________________ is the first step of the light reactions © 2011 Pearson Education, Inc.

40. There are _______ types of photosystems in the thylakoid membrane _____________________ functions first (the numbers reflect order of discovery) and is best at absorbing a wavelength of ______________ The reaction-center chlorophyll a of PS II is called ____________ © 2011 Pearson Education, Inc.

41. ____________________ is best at absorbing a wavelength of ________________ The reaction-center chlorophyll a of PS I is called _______________ © 2011 Pearson Education, Inc.

42. Linear Electron Flow During the light reactions, there are two possible routes for electron flow: ________ and _______ ________________________, the primary pathway, involves both photosystems and produces ATP and NADPH using light energy © 2011 Pearson Education, Inc.

43. A photon hits a pigment and its energy is passed among pigment molecules until it excites ______ An excited electron from P680 is transferred to the _________________________________ (we now call it ___________) © 2011 Pearson Education, Inc.

44. P680 + is a very strong ______________ agent __________ is split by enzymes, and the electrons are transferred from the hydrogen atoms to P680 +, thus reducing it to P680 ____________ is released as a by-product of this reaction © 2011 Pearson Education, Inc.

45. Each electron “__________” down an electron transport chain from the primary electron acceptor of PS II to PS I Energy released by the fall drives the creation of a _______________ across the thylakoid membrane Diffusion of H + (protons) across the membrane drives __________________ © 2011 Pearson Education, Inc.

46. In _________ (like PS II), transferred light energy excites P700, which loses an electron to an electron acceptor ____________ (P700 that is missing an electron) accepts an electron passed down from PS II via the electron transport chain © 2011 Pearson Education, Inc.

47. Each electron “falls” down an electron transport chain from the primary electron acceptor of PS I to the protein _____________ The electrons are then transferred to _____________ and reduce it to __________ The electrons of NADPH are available for the reactions of the ______________ cycle This process also removes an _____ from the stroma © 2011 Pearson Education, Inc.

48. 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

49. 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

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

51. Figure 10.16 Photosystem I Primary acceptor Cytochrome complex Fd Pc ATP Primary acceptor Pq Fd NADPH NADP  reductase NADP  + H  Photosystem II

52. Some organisms such as ____________________ have PS I but not PS II ____________________ is thought to have evolved before linear electron flow Cyclic electron flow may protect cells from ______________________ © 2011 Pearson Education, Inc.

53. A Comparison of Chemiosmosis in Chloroplasts and Mitochondria Chloroplasts and mitochondria generate ATP by ________________, but use different sources of energy Mitochondria transfer _________________ from food to ATP; chloroplasts transform ____________ into the chemical energy of ATP __________________ of chemiosmosis differs between chloroplasts and mitochondria but also shows similarities © 2011 Pearson Education, Inc.

54. In mitochondria, protons are pumped to the _________________ and drive ATP synthesis as they diffuse back into the mitochondrial matrix In chloroplasts, protons are pumped into the ________________ and drive ATP synthesis as they diffuse back into the stroma © 2011 Pearson Education, Inc.

55. 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

56. _______________________ are produced on the side facing the stroma, where the ______________________ takes place In summary, light reactions ________________ and increase the potential energy of electrons by moving them from ____________________ © 2011 Pearson Education, Inc.

57. 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

58. Concept 10.3: The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO 2 to sugar The _________________, like the citric acid cycle, regenerates its starting material after molecules enter and leave the cycle The cycle builds ___________ from smaller molecules by using __________ and the reducing power of electrons carried by ______________ © 2011 Pearson Education, Inc.

59. Carbon enters the cycle as CO 2 and leaves as a sugar named ________________________ For net synthesis of 1 G3P, the cycle must take place ___________, fixing ___ molecules of CO 2 The Calvin cycle has three phases –_______________ (catalyzed by _________) –_______________ –____________________________________ © 2011 Pearson Education, Inc.

60. 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

61. Concept 10.4: Alternative mechanisms of carbon fixation have evolved in hot, arid climates _________________ is a problem for plants, sometimes requiring trade-offs with other metabolic processes, especially photosynthesis On hot, dry days, plants close ________, which conserves _____ but also limits _____________ The closing of stomata reduces access to ______ and causes __________ to build up These conditions favor an apparently wasteful process called __________________________ © 2011 Pearson Education, Inc.

62. Photorespiration: An Evolutionary Relic? In most plants (_____________), initial fixation of CO 2, via ____________, forms a ___________ compound (3-phosphoglycerate) In photorespiration, rubisco adds ____ instead of _____ in the Calvin cycle, producing a ______________ compound Photorespiration consumes ____ and ______________ and releases ______ without producing ATP or sugar © 2011 Pearson Education, Inc.

63. Photorespiration may be an evolutionary relic because rubisco first evolved at a time when the atmosphere had far less O 2 and more CO 2 Photorespiration limits damaging products of light reactions that build up in the absence of the Calvin cycle In many plants, photorespiration is a problem because on a hot, dry day it can drain as much as ______ of the carbon fixed by the Calvin cycle © 2011 Pearson Education, Inc.

64. C 4 Plants ______________ minimize the cost of photorespiration by incorporating CO 2 into ______________ compounds in mesophyll cells This step requires the enzyme _____________ PEP carboxylase has a higher affinity for _____ than rubisco does; it can __________ even when CO 2 concentrations are low These four-carbon compounds are exported to ______________, where they release ______ that is then used in the Calvin cycle © 2011 Pearson Education, Inc.

65. Figure 10.20 C 4 leaf anatomy The C 4 pathway Photosynthetic cells of C 4 plant leaf Mesophyll cell Bundle- sheath cell Vein (vascular tissue) Stoma Mesophyll cell PEP carboxylase CO 2 Oxaloacetate (4C) PEP (3C) Malate (4C) Pyruvate (3C) CO 2 Bundle- sheath cell Calvin Cycle Sugar Vascular tissue ADP ATP

66. In the last 150 years since the Industrial Revolution, _________ levels have risen greatly Increasing levels of CO 2 may affect C 3 and C 4 plants differently, perhaps changing the ______________________ of these species The effects of such changes are unpredictable and a cause for concern © 2011 Pearson Education, Inc.

67. CAM Plants Some plants, including ________________, use _______________________________ to fix carbon ________________ open their stomata at night, incorporating CO 2 into organic acids ________________ close during the _______, and CO 2 is released from organic acids and used in the Calvin cycle © 2011 Pearson Education, Inc.

68. Sugarcane Mesophyll cell Bundle- sheath cell C4C4 CO 2 Organic acid CO 2 Calvin Cycle Sugar (a) Spatial separation of steps (b) Temporal separation of steps CO 2 Organic acid CO 2 Calvin Cycle Sugar Day Night CAM Pineapple CO 2 incorporated (carbon fixation) CO 2 released to the Calvin cycle 21 Figure 10.21

69. The Importance of Photosynthesis: A Review The energy entering chloroplasts as sunlight gets stored as _____________________________ Sugar made in the chloroplasts supplies chemical energy and carbon skeletons to synthesize the organic molecules of cells Plants store excess sugar as _________ in structures such as ________________________ In addition to food production, photosynthesis produces the _____ in our atmosphere © 2011 Pearson Education, Inc.