Photosynthesis: Using Light to Make Food

1. 0 Chapter 7 Photosynthesis: Using Light to Make Food

2. Write 5 things that you ate in the past 24 hours. DO NOW

3. 0 Photosynthesis is the process by which certain organisms use light energy to make sugar and oxygen gas from carbon dioxide and water http://www.youtube.com/watch?v=C1_uez5WX1o Light energy CO2 H2O C6H12O6 O2 6 + 6 + 6 Carbon dioxide Water Glucose Oxygen gas PHOTOSYNTHESIS

4. 0 As the human demand for energy grows Fossil fuel supplies are dwindling Energy plantations Are being planted to serve as a renewable energy source

5. 0 • 7.1 Autotrophs are the producers of the biosphere • Plants are autotrophs • Producing their own food and sustaining themselves without eating other organisms AN OVERVIEW OF PHOTOSYNTHESIS

6. Producers Are autotrophs. Manufacture the biosphere's food supply. Make organic food molecules from simple raw materials. Sustain themselves without eating. Consumer Must eat in order to survive.

7. 0 Plants, algae, and some bacteria are photoautotrophs Produce organic molecules from inorganic molecules. Utilize light as their energy source Figure 7.1A–D

8. Mesophyll Cell Leaf Cross Section Leaf Mesophyll LM 2,600  Chloroplast 7.2 Photosynthesis occurs in chloroplasts In plants, photosynthesis occurs primarily in the leaves. Vein Stoma O2 CO2 Chloroplast Outer membrane TEM 9,750  Inner membrane Stroma Intermembrane space Stroma Grana Thylakoid Granum Thylakoid space Figure 7.2

9. Stomata (Stoma)-tiny pores on the underside of a leaf that allow carbon dioxide, oxygen, and water to enter/exit. Mesophyll-green tissue on the interior of the leaf Chloroplast-where photosynthesis occurs Chlorophyll-light-absorbing pigment

10. Chloroplasts Composed of two membranes with an intermembrane space Stroma- Thick fluid where sugars are made ThylakoidMembrane- system of interconnected membranous sacs. where chlorophyll is found Grana- disklike membranous sacs arranged in stacks.

12. Experiment 1 6 CO2 12 H2O C6H12O6 6 H2O + 6 O2 + + Not labeled Experiment 2 7.3 Plants produce O2 gas by splitting water The oxygen released into the air as a product of photosynthesis comes from water. 6 H2O + 6 O2 6 CO2 12 H2O C6H12O6 + + Labeled 6 CO2 12 H2O Reactants: Products: C6H12O6 6 O2 Figure 7.3A–C 6 H2O

13. 0 7.4 Photosynthesis is a redox process, as is cellular respiration In photosynthesis H2O is oxidized and CO2 is reduced Light is the source of energy that provides the boost for electrons during photosynthesis Reduction   6 O2 6 CO2 6 H2O C6H12O6 Oxidation Oxidation   C6H12O6 6 CO2 6 H2O 6 O2 Figure 7.4A, B Reduction

14. 0 7.5 Overview: Photosynthesis occurs in two stages linked by ATP and NADPH The complete process of photosynthesis consists of two linked sets of reactions The light reactions and the Calvin cycle

15. Light Reactions Occurs in the thylakoid membrane Convert light energy to chemical energy and produce O2 gas as a waste product ATP, NADPH, O2 are produced

16. Calvin Cycle Occurs in the stroma Cyclic series of reactions that assemble sugar molecules using CO2 and the energy-containing products of the light reactions. Glucose, ADP, NADP+ are produced. CarbonFixation- occurs when carbon and oxygen from CO2 are incorporated into an organic molecule.

17. 0 H2O CO2 Chloroplast Light NADP+ The light reactions Convert light energy to chemical energy and produce O2 The Calvin cycle assembles sugar molecules from CO2 Using ATP and NADPH from the light reactions ADP + P CALVIN CYCLE (in stroma) LIGHT REACTIONS (in thylakoids) ATP Electrons NADPH Figure 7.5 O Sugar

18. 0 THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY Increasing energy 1 nm 1 m 10–5 nm 10–3 nm 103 nm 106 nm 103 m Micro- waves Radio waves Gamma rays X-rays UV Infrared 7.6 Visible radiation drives the light reactions Certain wavelengths of visible light, absorbed by pigments, drive the light reactions of photosynthesis Light Reflected light Visible light 400 500 600 700 750 380 Wavelength (nm) Absorbed light Chloroplast 650 nm Transmitted light Figure 7.6A, B

19. Electromagnetic Energy- energy that travels in waves. Ex. Sunlight Chlorophyll a-Participates directly in the light reactions. Ex. Most plants are green because Chlorophyll a reflects green light. Chlorophyll b-Passes absorbed energy to chlorophyll a. Photon-fixed quantity of light energy

20. 0 7.7 Photosystems capture solar power Thylakoid membranes contain multiple photosystems, that absorb light energy, which excites electrons Figure 7.7A

21. 0 Each photosystem consists of Light-harvesting complexes of pigments A reaction center with a primary electron acceptor that receives excited electrons from a reaction-center chlorophyll The reaction centers of photosystem I and II absorb slightly different wavelengths of light. Photosystem Primary electron acceptor Reaction center Light-harvesting complexes Photon Excited state To electron transport chain e– Heat e– Thylakoid membrane Energy of electron Photon Photon (fluorescence) Ground state Figure 7.7B, C Pigment molecules Chlorophyll molecule Transfer of energy Chlorophyll a molecule

22. 0 7.8 In the light reactions, electron transport chains generate ATP and NADPH Two connected photosystems absorb photons of light and transfer the energy to chlorophyll. Electrons removed from water molecules pass from photosystem II to photosystem I to NADP+.

23. Photon Photon Photosystem II Photosystem I + H+ NADPH NADP+ Stroma 1 6 The excited electrons Are passed from the primary electron acceptor to electron transport chains e– 2 e– Thylakoid membrane 4 5 P700 P680 Thylakoid space 3 Electron transport chain Provides energy for synthesis of by chemiosmosis ATP H2O 1 O2 + 2 H+ 2 Figure 7.8A

24. e– ATP Electrons shuttle from photosystem II to I Providing energy to make ATP Electrons from photosystem I Reduce NADP+ to NADPH e– e– NADPH e– e– e– Mill makes ATP Photon e– Photon Photosystem II Photosystem I Figure 7.8B

25. As a result of the cascade of electrons down the electron transport chains of the light reactions, NADP+ is reduced to NADPH. Photosystem II regains electrons by splitting water, releasing O2 Water moleculesNADP+which is reduced toNADPH, the source of electrons in the Calvin Cycle

26. 7.9 Chemiosmosis powers ATP synthesis in the light reactions The electron transport chain pumps H+ into the thylakoid space The diffusion of H+ back across the membrane through ATP synthase powers the phosphorylation of ADP to produce ATP (photophosphorylation)

27. Chloroplast Stroma (low H+ concentration) H+ H+ Light Light ADP + P ATP H+ NADP+ H+ NADPH The final electron acceptor in oxidative phosphorylation is O2, while it is NADP+ in photophosphorylation. + H+ Thylakoid membrane H+ H+ H2O 1 H+ H+ H+ H+ + O2 H+ 2 H+ H+ 2 H+ Photosystem II Electron transport chain Photosystem I ATP synthase H+ Thylakoid space (high H+ concentration) Figure 7.9

28. Chemiosmosis • http://www.youtube.com/watch?v=eY1ReqiYwYs • Transition • http://www.youtube.com/watch?v=Bdc-fHn0zAU&feature=related

29. THE CALVIN CYCLE: CONVERTING CO2 TO SUGARS CO2 ATP NADPH Input 7.10 ATP and NADPH power sugar synthesis in the Calvin cycle The Calvin cycle occurs in the chloroplast’s stroma CALVIN CYCLE Output: G3P Figure 7.10A

30. 1 Input: 3 CO2 1 P 3 P P 6 RuBP 2 3-PGA 6 The cycle constructs G3P, an energy-rich molecule that a plant cell can then use to make glucose or other organic molecules. ATP 3 ADP 6 ADP + P CALVIN CYCLE 3 ATP 4 2 6 NADPH 3 6 NADP+ 5 P 6 P G3P G3P 3 4 Figure 7.10B Glucose and other compounds P 1 Output: G3P

31. PHOTOSYNTHESIS REVIEWED AND EXTENDED H2O CO2 Chloroplast Light NADP+ ADP P + 7.11 Review: Photosynthesis uses light energy to make food molecules The ultimate source of all the food we eat and the oxygen we breathe is photosynthesis. RUBP Photosystem II CALVIN CYCLE (in stroma) Electron transport chains 3-PGA Thylakoid membranes Photosystem I ATP Stroma Cellular respiration NADPH G3P Cellulose Starch O2 Sugars Other organic compounds Figure 7.11 LIGHT REACTIONS CALVIN CYCLE

32. 7.12 C4 and CAM plants have special adaptations that save water In C3 plants a drop in CO2 and rise in O2 when stomata close on hot dry days divert the Calvin cycle to photorespiration C4 and CAM plants help the plant conserve water and synthesize glucose efficiently under hot, dry conditions.

33. CO2 Mesophyll cell 4-C compound C4 plants first fix CO2 into a four-carbon compound that provides CO2 to the Calvin cycle CO2 CALVIN CYCLE Sugarcane 3-C sugar Bundle-sheath cell C4 plant Figure 7.12 (left half)

34. CO2 CO2 Night 4-C compound CAM plants open their stomata at night making a four-carbon compound used as a CO2 source during the day CO2 CALVIN CYCLE Pineapple 3-C sugar Day Figure 7.12 (right half) CAM plant

35. Do photosynthesizing plants have mitochondria? Why or why not? • Yes, to supply the plant with the ATP needed to power various cell activities.

36. PHOTOSYNTHESIS, SOLAR RADIATION, AND EARTH’S ATMOSPHERE CONNECTION 7.13 Photosynthesis moderates global warming Greenhouses used to grow plants Trap solar radiation, raising the temperature inside Figure 7.13A

37. Some heat energy escapes into space Sunlight ATMOSPHERE Excess CO2 in the atmosphere is contributing to global warming Radiant heat trapped by CO2 and other gases Figure 7.13B

38. Photosynthesis, which removes CO2 from the atmosphere, moderates this warming

39. TALKING ABOUT SCIENCE 7.14 Mario Molina talks about Earth’s protective ozone layer Figure 7.14A

40. Solar radiation converts O2 high in the atmosphere to ozone (O3) Which shields organisms on the Earth’s surface from the damaging UV radiation

41. Southern tip of South America Industrial chemicals called CFCs (chlorofluorocarbons) have caused dangerous thinning of the ozone layer But international restrictions on CFC use are allowing recovery Antarctica Figure 7.14B