photosynthesis

• Photosynthesis


  The process by which plants convert sunlight, carbon dioxide and water into glucose and oxygen
• Photosynthesis was developed 450 million years ago
• Reactions in photosynthesis


  • Light dependent reactions
  • Light independent reactions (Calvin cycle)
• Light dependent reactions


  Reactions that require light energy
• Photosynthesis is basically respiration in reverse
• Requirements for photosynthesis


  • Water
  • Carbon dioxide
  • Sunlight
• How plants obtain requirements for photosynthesis

  1. Roots absorb water and transport it to leaves through xylem

  2. Carbon dioxide enters and oxygen exits through stomata in leaves

  3. Chlorophyll in leaves absorbs sunlight
• Chloroplast


  • Contains thylakoid membranes with chlorophyll
  • Contains stroma outside thylakoids
• Light dependent reactions


  1. Chlorophyll absorbs photon

  2. Electron in chlorophyll becomes excited

  3. Electron transported through electron transport chain

  4. Energy used to pump protons into thylakoid lumen

  5. ATP synthase uses proton gradient to produce ATP

  6. Electrons also used to produce NADPH
• Oxygen is a byproduct of the light dependent reactions