Exploring Photosynthesis: From Light to Glucose

1. Do Now • What does a chloroplast look like? • How do plants obtain energy? • What is the formula for glucose? • How do autotrophs obtain energy? • How do heterotrophs obtain energy?

2. Chapter 6 Photosynthesis: Capturing and Converting Energy

3. Energy – the ability to do work

4. Photosynthesis • Plants use the energy of sunlight to produce carbohydrates • Energy is now in the chemical bonds

5. Jan Van Helmont • Where does a tree’s increased mass come from? • Seedling – 5 years – soil same mass – tree gained 75 kg • Conclusion  water “hydrate”

6. Priestly • Candle and a jar  candle goes out – no oxygen • Candle + jar + plant  candle does not go out

7. Ingenhousz • Oxygen produced in light

8. Equation for Photosynthesis

11. Requirements for Photosynthesis

12. 1. Sunlight • Autotrophs – can use sunlight to make food • Ex. Plants obtain energy • Heterotrophs – obtain energy by eating other organisms • Ex. Animals • All organisms on earth depend on the sun for energy

13. Sunlight is “white” light • Many wavelengths of light • ROYGBIV – visible spectrum

14. 2. Pigments • Colored substances that absorb or reflect light • Photosynthesis begins when light is absorbed by pigments • Chlorophyll – principle pigment of green plants • Absorbs red and blue and reflects green light

15. Chromatography • Paper chromatography is a way to separate chemical components of a solution. • How it Works • A drop of solution is placed at the bottom of a paper. • The paper is put in a solvent (tip only). • The solvent rises through the paper. • As it rises it carries the solution with it. • The parts of the solution move at different speeds depending on their mass. Lighter molecules move faster.

16. 3. Energy Storing Compounds • Like solar cells • Electrons are raised to higher energy levels – then trapped in bonds • Two ways that energy from the sun is trapped in chemical bonds

17. High energy e- are passed to an electron carrier • (NADP +)  NADPH • Electron carrier – a molecule that can accept a pair of high energy electrons and later transfer them with most of their energy to another compound • Conversion of NADP+ to NADPH – one way that energy from the sun can be trapped in a chemical form

18. Second way light energy is trapped  ATP (Adenosine Triphosphate) – 3 phosphates • Fig 6-6 • Green plants produce ATP in photosynthesis • ATP energy storage compound used by every cell

19. Producing ATP • AMP (mono) – one phosphate • AMP + P  ADP (two – di) • ADP + P  ATP • Energy is stored in the P bonds • Energy is released when P bonds are broken

22. Section 9.1 Summary – pages 221-224 Forming and Breaking Down ATP P P P Adenosine Adenosine triphosphate (ATP) P P Adenosine diphosphate (ADP) P P Adenosine

23. 6-2 Photosynthesis: The Light and Dark Reactions • Light Reaction – energy of sunlight captured to make energy storing compounds • ATP and NADPH • Short term energy storage

24. Section 9.2 Summary – pages 225-230 Sun Light-Dependent Reactions Light energy transfers to chlorophyll. At each step along the transport chain, the electrons lose energy. Chlorophyll passes energy down through the electron transport chain. Energized electrons provide energy that splits H2O to ADP bonds P forming ATP oxygen released H+ NADP+ NADPH for the use in light-independent reactions

25. Dark Reaction – energy from ATP and NADPH to make glucose (100 x the energy) • Long term energy storage

26. The Light Reactions

27. Chloroplast • Parts of a chloroplast • Stroma – “cytoplasm” • Grana – pancake • Thylakoid – stacks of pancakes (grana) • Thylakoid = photosynthetic membrane

29. 4 Parts of the Light Reaction • Light absorption • Electron transport • Oxygen production • ATP formation

30. Photosystems • Clusters of pigment molecules that capture energy from the sun • Two in plants – Photosystems I and II

31. Photosynthesis – plants - autotrophs • Occurs in the chloroplast • Absorbs light • Light reaction occurs in the thylakoid (photosynthetic environment) – needs sun to occur

32. Light Absorption • Photosystem I & II – absorb sunlight • Pigment molecules pass the energy to other pigment molecules • Reach a special pair of chlorophyll molecules in the reaction center • High energy electrons released and passed to many electron carriers

33. Electron Transport • Electron transport – electron transport chain • e- passed from one carrier to another (bucket brigade) • Passed to electron carrier NADP+ • NADPH

34. Electron Transport Chain

35. NADPH – restoring electrons • Water is split (photolysis) • 2 H2O  4 H+ + O2 + 4 e- • Oxygen is released • 4 e- go to the chloroplast • 4 H+ are used to make ATP

37. ATP Formation • 4 H+ released inside the membrane • H+ build up • Inside positive – outside is negative (charge difference is a source of energy) • Enzymes use this energy to • attach P to ADP  ATP

39. The Dark Reaction or Calvin Cycle

40. The Dark Reaction or Calvin Cycle • Does not need sunlight to happen • Often happens with sunlight • Uses products of the light reaction (ATP + NADPH) • This series of reactions is particularly critical to living things • Carbon dioxide is used to build complex organic molecules  glucose

41. Dark Reaction or Calvin Cycle • Occurs in the stroma • 5 C sugar (RuBP) + CO2 • This reaction is slow and is catalyzed by rubisco • Next two 3 C sugars are produced (PGA) • ATP and NADPH from the light reaction are used to convert PGA eventually into PGAL (3 C) – products P + ADP and NADP+ • PGAL can use some ATP and become RuBP (5 C) • After several turns of the cycle 2 PGAL can leave and form glucose

44. 6-3 Glycolysis and Respiration

45. Enables organisms to release energy in glucose • Breaks down food molecules • C6H12O6 + 6O2 6CO2 + 6H2O + energy (ATP) • 1 g of glucose  3811 calories • 1 cal = amount of heat energy to raise • 1 g of water 1 OC

46. Glycolysis • occurs in the cytoplasm • Changes a molecule of glucose into many different molecules step by step

47. Glucose (6 C) • 2 ATP are used to make 2-3-C PGAL • PGAL is converted into pyruvic acid and 4 ATP and 2 NADH are produced • Pyruvic acid can enter aerobic or anaerobic respiration based on whether there is oxygen available or not

48. Presence of Oxygen – Cellular Respiration • Aerobic oxygen needed • Takes place in the mitochondria • Krebs cycle (Citric Acid Cycle) • Starts with Pyruvic acid • Carbon dioxide is removed • Acetyl CoA is produced • Citric acid is then produced • 9 reactions • 9 intermediate • citric acid is produced and the cycle begins again • Carbon dioxide is released • Make FADH2 and NADH

49. FADH2 and NADH go to the inner membrane of the mitochondria • Electrons passed to enzymes • Electron transport chain • At the end – enzyme combines • H+ + O2  H2O • Therefore Oxygen is the final electron acceptor • Mitochondrial membrane is charged (H+ ions pumped to one side) • Provides energy to convert ADP  ATP • 36 ATP are produced