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Photosynthesis (overview)


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Made in 2014

Published in: Science
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Photosynthesis (overview)

  1. 1. PHOTOSYNTHESIS The Most Important Chemical Process on Earth
  2. 2. “light” “to make or compose”
  3. 3. • food-making process in plants • process by which green plants convert light energy into chemical energy • complex chemical reaction or process by which plants put together carbohydrates • also called photophosphorylation and carbon fixation
  4. 4. Nature of Light
  5. 5. The Leaf
  6. 6. Process Location Reactants Products Light Dependent Reactions (Photosystems) Thylakoid membranes • sunlight • H2O • ATP • NADPH • O2 Light Independent Reactions (Calvin Cycle) Stroma • ATP • NADPH • CO2 sugar
  7. 7. Aristotle Jan Baptista van Helmont Stephen Hales Joseph Priestly Jan IngenhouszJean SenebierNicolas de SaussureRuben and Kamen
  8. 8. • since plants grew from the soil, it seemed evident to Aristotle that their substance must come from the soil • regarded the soil as equivalent to a vast stomach that prepares and supplies the food of plants
  9. 9. • considered water to be the source of life and the basic nutrient for plants • demonstrated that soil contributes very little to the increase in weight of plants and it must be water
  10. 10. • recognized the importance of light and air in plant nourishment • described the leaves as organs of transpiration and he postulated that plants exchange gases with their surrounding air
  11. 11. • unknowingly discovered oxygen and demonstrated that plants produce the gas • was the first to prove the different qualities of the gases released by plants and the ones exhaled by animals
  12. 12. • demonstrated the importance of light in the production of oxygen by green plants • systematically investigated the release of air from green parts of plants during day time especially from the lower side of leaves
  13. 13. Device used by Ingenhousz to investigate photosynthesis
  14. 14. • showed the importance of a “fixed air” (carbon dioxide) in the process • showed that plants absorb carbon dioxide and release oxygen (dephlogisticated air)
  15. 15. • showed the importance of water for the production of organic materials by the plants • verified Ingenhousz´s hypothesis that plants assimilate carbon dioxide from the air while nitrogen and other nutrients are derived from the soil
  16. 16. • revised the basic equation into 2 types of reactions as: Light reaction: 2H2O + light → 4H + O2 Dark reaction: 4H + CO2 → CH2O + H2O
  17. 17. During 1900s – extensive studies on photosynthesis arise and equation of photosynthesis had been formulated as: 6CO2 + 6H2O C6H12O6 + 6O2 light chlorophyll 6CO2 + 12H2O C6H12O6 + 6H2O + 6O2 light chlorophyll Revised (by Ruben and Kamen):
  18. 18. The Nature of Light Light – considered to have both particle and wave nature Photons  particles or packets of light  smallest divisible units of light  move in wave-like behavior  carry a fixed amount of energy Wave  characterized by  wavelength  frequency c = 299,792,458 m/s or 3 x 108 m/s
  19. 19.  distance between two light waves  distance moved by a photon during one of its vibrations  distance from peak to peak (or trough to trough)
  20. 20.  the shorter the wavelength, the more energy each photon contains  arranged from shorter to longer wavelengths known as electromagnetic spectrum  measured in nanometers (nm)
  21. 21.  sunlight is composed of different colors (ROYGBIV)  leaves absorb all colors except green  pigments in leaves absorb those wavelengths within the visible light portion with a wavelength of 400-700 nm  theoretically, photosynthesis requires approximately 12 photons to convert one mole of CO2 to carbohydrates
  22. 22. 52%44% 4% Composition of Sunlight Infrared Visible Light Ultraviolet Back to Overview
  23. 23.  main photosynthetic organ of the plant  usually broad, flat and thin to ensure the exposure of all cells to light  usually green in color
  24. 24. Carbon dioxide enters, while oxygen exits through a leaf’s stomata  contains large number of stomata
  25. 25.  contains numerous chloroplasts containing the green pigment chlorophyll
  26. 26. Back to Overview
  27. 27. Power plants: Researchers explore how to harvest electricity directly from plants •Ramaraja Ramasamy (right) and •Yogeswaran Umansakar developed a way to interrupt photosynthesis modified thylakoids