8.3  Photosynthesis

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Essential Idea:

Light energy is converted

into chemical energy


  • Light-dependent reactions take place in the intermembrane space of the thylakoids
  • Light-independent reactions take place in the stroma
  • Reduced NADP and ATP are produced in the light-dependent reactions
  • Absorption of light by photosystems generates excited electrons
  • Photolysis of water generates electrons for use in the light-dependent reactions
  • Transfer of excited electrons occurs between carriers in thylakoid membranes
  • Excited electrons from Photosystem II are used to contribute to generate a proton gradient
  • ATP synthase in thylakoids generates ATP using the proton gradient
  • Excited electrons from Photosystem I are used to reduce NADP
  • In the light-independent reactions a carboxylase catalyses the carboxylation of ribulose bisphosphate
  • Glycerate-3-phosphate is reduced to triose phosphate using reduced NADP and ATP
  • Triose phosphate is used to regenerate RuBP and produce carbohydrates
  • Ribulose bisphosphate is reformed using ATP
  • The structure of the chloroplast is adapted to its function in photosynthesis


  • Calvin’s experiment to elucidate the carboxylation of RuBP


  • Annotation of a diagram to indicate the adaptations of a chloroplast to its function