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Photosynthesis is a process used by plants and other organisms to convert light energy, normally from the sun, into chemical energy that can be used to fuel the organisms' activities. Carbohydrates, such as sugars, are synthesized from carbon dioxide and water.

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  1. 1. History Of Photosynthesis
  2. 2. History Of Photosynthesis What does Photosynthesis Means? Site Of Photosynthesis Light & Dark Reaction Goal Of Photosynthesis
  3. 3. Investigating Photosynthesis •Many Scientists Have Contributed To Understanding Photosynthesis •Early Research Focused On The Overall Process •Later Researchers Investigated The Detailed Chemical Pathways
  4. 4. Van Helmont’s Experiment 1643 • Van Helmont planted a seed into a pre-measured amount of soil and watered for 5 years • He weighed plant & soil. Plant was 75 kg, soil the same. • He concluded that “Mass Came From Water”
  5. 5. Priestley’s Experiment 1771 • He burned candle in Bell Jar Until it went out. • Placed sprig of Mint in Bell Jar for a Few Days. • Candle could be relit and burnt. • He concluded that “Plants released substance (O2) necessary for burning.”
  6. 6. Ingenhousz’s Experiment 1779 Ingenhousz repeated Priestly experiment with & without sunlight
  7. 7. Results of Ingenhousz’s Experiment • He showed that Priestley‟s results occurred only in the presence of Sunlight. • “Light was necessary for plants to produce the „Burning Gas‟ or Oxygen.”
  8. 8. What does Photosynthesis means? – Photosynthesis is the process by which certain organisms use light energy • To make sugar and oxygen gas from carbon dioxide and water Light energy PHOTOSYNTHESIS 6 CO2 6+ H2O Carbon dioxide Water C6H12O6 6+ O2 Glucose Oxygen gas
  9. 9. • Photosynthesis is a chemical process in which energy from light is harvested to provide carbohydrates. • It is the major path through which Carbon reenters the biosphere (from CO2). • Photosynthesis is also the major source of Oxygen in the earth's atmosphere What does Photosynthesis means?
  10. 10. • Chloroplast is the place where Photosynthesis occurs. • Photosynthesis occurs in the following parts of Chloroplast:-  Grana  Stroma Site Of Photosynthesis
  11. 11. Grana:- They are sac like structures present in the chloroplast. The light reaction takes place in grana. Stroma:- They are the spaces surrounding the Grana. They are site for dark reaction. They are aqueous & contain RNA, DNA & Ribosomes. Grana & Stroma
  12. 12. The capturing of light energy occurs within the chloroplasts, primarily located in the mesophyll cells of the leaf. The major light absorbing pigments on thylakoid membrane is chlorophyll. Light Harvesting Pigments
  13. 13. Light & Dark Reaction
  14. 14. • Light-dependent reactions occur on the thylakoid membranes. – Light and water are required for this process. – Energy storage molecules are formed. (ATP and NADPH) – Oxygen gas is made as a waste product. Light Reaction
  15. 15. • New electron need to be taken from water to allow the process to continue. • 4 electrons are removed from 2 water molecule leaving 4H+ ion and 2 oxygen atom. • The 2 oxygen atom from O2 gas that is released into the air to be consumed by the heterotrophs and used in cellular respiration. Oxygen Production
  16. 16. • From the chlorophyll , electrons are passed from one molecule to another down an electron transport chain. • The light energy electrons end up at the electron carrier molecule NADP+ • Converting it into NADPH. • This energy storing molecule will be used in dark reaction. Electron Transport
  17. 17. ATP and NADPH, generated by light reaction are used to fix and reduce CO2 to form carbohydrate. ATP + NADPH +H++ CO2 C6H12O6 Enzymes and intermediates of the cycle are located in the chloroplast stroma. Dark Reaction (Calvin Cycle)
  18. 18. • From the splitting of water, the H+ ions left behind create a difference in charge across the photosynthesis membrane. • The inside of the membrane is positive and outside is negative. • A proton pump called ATPsynthase make ATP (to be used in dark reaction) by attaching H+ ions to ADP. • This process is called Chemiosmosis. Formation Of ATP
  19. 19. • Reduction of carbon dioxide into carbohydrate via the oxidation of energy carriers (ATP, NADPH) • Light reactions energize the carriers • Dark reactions (Calvin Cycle) produce PGAL (phosphoglyceraldehyde) Photosynthesis 6CO2 +6H20 + light C6H1206 + 6O2 Photosynthesis Equation
  20. 20. • The “goal” of photosynthesis is to synthesize glucose. –Carbon dioxide is reduced to glucose (see equation below). –The electrons needed for this reduction come from water. –The energy needed for this reduction comes from light (ATP, NADPH). –The equation is: Energy + 6CO2 + 6H2O C6H12O6 + 6O2 Goal Of Photosynthesis
  21. 21. • Photosynthesis does NOT supply energy to the cell. Photosynthesis USES light energy to make organic compounds. • To get energy for the cell, plant cells must use cellular respiration to break down glucose and make ATP. Important Note On Photosynthesis
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