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Photosynthesis

Photosynthesis. Textbook pages 97 – 103. Photosynthesis . process used by plants using light energy to create sugar (glucose, C 6 H 12 O 6 ) from carbon dioxide (CO 2 ) and water (H 2 O) oxygen gas ( O 2 ) is produced as a waste product and the light energy used is stored as chemical energy.

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Photosynthesis

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  1. Photosynthesis Textbook pages 97 – 103

  2. Photosynthesis • process used by plants using light energy to create sugar (glucose, C6H12O6) from carbon dioxide (CO2) and water (H2O) • oxygen gas (O2) is produced as a waste product and the light energy used is stored as chemical energy

  3. Investigating Photosynthesis • Jan Van Helmont (1643) • Carefully massed soil, and tree seedling and watered over 5 years. • Determined most of the mass of the tree came from water.

  4. Investigating Photosynthesis • Joseph Priestley (1771) • Lit a candle and placed a bell jar over it, watching the flame go out. • Reasoned that there was something in the air necessary to keep the flame going. • When a plant was placed under the bell jar, discovered that the candle could be relit after several days. • Reasoned that the plant released something into the air necessary for the flame.

  5. Investigating Photosynthesis • Jan Ingenhousz (1779) • Showed the effect observed by Priestley only occurred when plants were exposed to light.

  6. Investigating Photosynthesis • Julius Robert Mayer (1845) • Proposed that plants convert light energy into chemical energy

  7. Photosynthesis Equation 6 CO2+ 6 H2O + light energy  C6H12O6 + 6 O2

  8. Stages of Photosynthesis • Capture energy from sunlight • Convert light energy into chemical energy • Use stored chemical energy to produce organic compounds (food) from carbon dioxide

  9. 1. Capture energy from sunlight

  10. 1. Capture energy from sunlight • Pigments (chlorophyll) in the membranes of the thylakoids absorb light energy • Gets transferred to electrons • Electrons are replaced from water • H+ ions are left • Remaining O from into O2 gas as waste product

  11. 2. Converting light energy to chemical energy

  12. 2. Converting light energy to chemical energy • Light dependent reactions • Occurs in thylakoid membranes • Use high-energy electrons to produce two high-energy products • Convert ADP into ATP • Convert NADP+ into NADPH

  13. 2. Converting light energy to chemical energy

  14. 2. Converting light energy to chemical energy • Electron transport chains (ETC) • A series of molecules through which excited electrons are passed • Energy from the electrons is used to pump H+ ions across the thylakoid membrane • A second ETC provides energy to make NADPH, a high energy electron carrier

  15. 2. Converting light energy to chemical energy

  16. 2. Converting light energy to chemical energy • Production of ATP • A concentration gradient is present now for H+ ions • Passing of ions back out of the thylakoid provides energy to make ATP

  17. 2. Converting light energy to chemical energy

  18. 2. Converting light energy to chemical energy • Both ATP and NADPH are used in the next step • ATP carries necessary energy • NADPH carries high-energy electrons

  19. 3. Use stored chemical energy to make food

  20. 3. Use stored chemical energy to make food • Light independent reactions • Calvin Cycle is one example • Occur in stroma inside chloroplasts, but outside of thylakoids • Using energy from ATP and electrons from NADPH, CO2 is fixed into sugars

  21. Investigating Photosynthesis • Melvin Calvin (1948) • received the Nobel prize in chemistry (1961) for discovering pathways that carbon follows to make glucose in photosynthesis

  22. Factors that affect Photosynthesis • light intensity • CO2 concentration • water levels • temperature

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