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Explain: Converting Sunlight into Energy

Explain: Converting Sunlight into Energy. Photosynthesis. Energy: Capacity to do work Forms of energy: Chemical (Food and Gas) Light Electrical Mechanical Organisms store energy in the organic molecules from which mechanical organisms are made (Chemical Energy).

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Explain: Converting Sunlight into Energy

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  1. Explain: Converting Sunlight into Energy

  2. Photosynthesis • Energy: Capacity to do work • Forms of energy: • Chemical (Food and Gas) • Light • Electrical • Mechanical • Organisms store energy in the organic molecules from which mechanical organisms are made (Chemical Energy)

  3. Remember: Energy is transferred from one form to another, never destroyed WEEEEE!!!

  4. What Plants Do Photosynthesis

  5. Photosynthesis • Photosynthesis: is an energy-storing process where light energy is converted to chemical energy in the form of sugars • Plants use Light Energy and convert it to Chemical Energy • Photosynthesis uses only certain wavelengths of visible light • In plants most light is absorbed by a green pigment called Chlorophyll • Plants are green because they reflect green light

  6. Chloroplasts • Thylakoid: are located in the chloroplasts and are highly organized arrangement of internal membranes. • Chlorophyll and enzymes are embedded • Grana: thylakoids form flattened stacks of disk shaped structures • Stroma: Solution that surrounds the thylakoid

  7. Adenosine triphosphate (ATP) • Chemical form of energy used in cells • Most important of several transfer compounds in all organisms • Is efficient and useful for energy transfer • Stores energy in high energy bonds between phosphates ATP = 3 Phosphates Breaking down ATP Releases Energy ADP = 2 Phosphates Adding a phosphate Stores Energy

  8. Happens in two phases • Light-Dependent Reaction • Converts light energy into chemical energy • Light-Independent Reaction • Produces simple sugars (glucose) • General Equation 6 CO2 + 6 H2O  C6H12O6 + 6 O2

  9. First Phase • Requires Light = Light Dependent Reaction • Sun’s energy energizes an electron in chlorophyll molecule • Electron is passed to nearby protein molecules in the thylakoid membrane of the chloroplast • Electron from Chlorophyll is passed from protein to protein along an electron transport chain • Electrons lose energy (energy changes form) • Finally bonded with electron carrier called NADP+ to form NADPH or ATP • Energy is stored for later use

  10. H2O CO2 Light NADP  ADP + P LIGHT REACTIONS CALVIN CYCLE ATP NADPH Chloroplast [CH2O] (sugar) O2 Figure 10.5 Carbon Dioxide 6 carbon molecules 6 carbon Sugars

  11. Two Photosystems • Photosystems: are complexes of chlorophyll (other pigments) and accessory proteins that act as light-harvesting centers • Each photosystem absorbs light and transfers its energy to a reactive chlorophyll molecule • There it excites and electron to increase energy levels

  12. A mechanical analogy for the light reactions In this "construction analogy" for the light reactions, the input of light energy is represented by the large yellow mallets. The light energy boosts the electrons up to their excited states atop the platform in each photosystem. The energy released as the electrons move down the electron transport chain between the photosystems is used to pump hydrogen ions across a membrane and produce ATP.

  13. Thylakoid Photosystem Photon STROMA Light-harvesting complexes Reaction center Primary election acceptor e– Thylakoid membrane Special chlorophyll a molecules Transfer of energy Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID) Figure 10.12 Photosystem • A photosystem • Is composed of a reaction center surrounded by a number of light-harvesting complexes

  14. Where those electrons come from • Water • Electrons from the splitting of water (photolysis) supply the chlorophyll molecules with the electrons they need • The left over oxygen is given off as gas

  15. Reactants: 12 H2O 6 CO2 6 H2O 6 O2 C6H12O6 Products: Figure 10.4 The Splitting of Water • Chloroplasts split water into • Hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules

  16. High Quality H2O • Photolysis – Splitting of water with light energy • Hydrogen ions (H+) from water are used to power ATP formation with the electrons • Hydrogen ions (charged particle) actually move from one side of the thylakoid membrane to the other • Chemiosmosis – Coupling the movement of Hydrogen Ions to ATP production

  17. Vocabulary Review • Light-Dependent Reaction • Converts light into chemical energy (ATP & NADPH are the chemical products). • Oxygen is a by-product • Chlorophyll • Green pigment in plants • Traps sun’s energy • Sunlight energizes electron in chlorophyll • Electron Transport Chain • Series of Proteins embedded in a membrane that transports electrons to an electron carrier

  18. Vocabulary Review • ATP (Adenosine Triphosphate) • Stores energy in high energy bonds between phosphates • NADPH • Made from NADP+; electrons and hydrogen ions • Made during light reaction • Stores high energy electrons for use during light-Independent reaction (Calvin Cycle)

  19. So where does the sugars come from? • The light reactions convert light energy to the chemical energy of ATP and NADPH. • But recall that photosynthesis also produces sugar. • So far no sugar has been produced. • That is the job of the Calvin cycle, which uses the ATP and NADPH produced by the light reactions.

  20. PART II • LIGHT INDEPENDENT REACTION • Also called the Calvin Cycle or “Dark Reaction” • No Light Required (as long as ATP and NADH are available) • Takes place in the stroma of the chloroplast • Takes carbon dioxide & converts into sugar • It is a cycle because it ends with a chemical used in the first step • Vital to organisms with chloroplasts, the calvin cycle makes it possible to produce energy in the form of glucose.

  21. H2O Input CO2 Light 3 (Entering one at a time) NADP+ CO2 ADP CALVINCYCLE LIGHTREACTION ATP NADPH Rubisco O2 [CH2O] (sugar) 3 P P Short-livedintermediate P 6 3 P P Ribulose bisphosphate(RuBP) 3-Phosphoglycerate 6 ATP 6 ADP CALVIN CYCLE 3 ADP 6 P P 3 ATP 1,3-Bisphoglycerate 6 NADPH 6 NADPH+ 6 P P 5 (G3P) 6 P Glyceraldehyde-3-phosphate (G3P) P 1 Glucose andother organiccompounds G3P(a sugar)Output Figure 10.18 Carbon Dioxide • The Calvin cycle Phase 1: Carbon fixation 6 carbon molecules Phase 3:Regeneration ofthe CO2 acceptor(RuBP) Phase 2:Reduction 6 carbon Sugars

  22. Chloroplast – Where the Magic Happens! + H2O CO2 Energy ATP and NADPH2 Which splits water Light is Adsorbed By Chlorophyll Calvin Cycle ADP NADP Chloroplast Used Energy and is recycled. O2 + C6H12O6 Light Reaction Dark Reaction 6 CO2 + 12 H2O + Light Energy→ C6H12O6 + 6 O2 + 6 H2O

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