Photosynthesis

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Photosynthesis

  1. 1. The Basic Facts• It is the conversion of light energy into chemical potential energy.• The energy is stored in organic molecules (e.g. ATP and glucose)• Carbon dioxide is reduced to produce carbohydrate• So, it needs a supply of electrons hydrogens and energy!
  2. 2. Chloroplast Structure1. outer membrane 5. thylakoid lumen (inside of 9. starch2. intermembrane space thylakoid) 10. ribosome3. inner membrane (1+2+3: 6. thylakoid membrane 11. plastidial DNA envelope) 7. granum (stack of thylakoids) 12. plastoglobule (drop of lipids)4. stroma (aqueous fluid) 8. thylakoid (lamella)
  3. 3. Light dependent stage (on thylakoid membranes)• The aim is to produce a supply of ATP (energy) and electrons that can be used to reduce carbon dioxide.• The electrons are carried by NADP (called reduced NADP or NADPH when it is carrying electrons).• Oxygen is released as a waste product.
  4. 4. Or put a different way… NADPH NADP lightwater dependent oxygen reaction ADP + P ATP
  5. 5. This is a blank slide for Mr King to do his own drawing on
  6. 6. Photolysis• Using light energy to split water into electrons, hydrogen ions and water.• H2O H+ + e- + O2• Replacing the electrons and hydrogen ions now carried by NADPH
  7. 7. summary• Chlorophyll absorbs light energy and its electrons are ‘excited’• ‘excited’ electrons pass through a series of carriers releasing energy to generate ATP from ADP and P (photophosphorylation)• Electrons are picked up by NADP• Light energy splits water and the electrons are used to replace missing electrons in chlorophyll• This all happens on membranes.
  8. 8. Light Independent stage• Energy from ATP, hydrogens and electrons from reduced NADP are used to reduce carbon dioxide to produce carbohydrate.• This happens in the stroma.
  9. 9. Light independent stage Reduced NADP NADPCarbon lightdioxide independent glucose reaction ATP ADP + Pi
  10. 10. (5C) Ribulose Biphosphate CO2 (1C) ATP 2X Glycerate-3-Phosphate(3C)NADPH ATP(3C) 2X Triose Phosphate Glucose (6C)
  11. 11. What happens without light?• Which stages can still continue when the light is turned off?• Which molecules will build up when the light is turned off?

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