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Englemanns experiment

  • experiment to determine which wavelengths of light most effective in photosynthesis
  • using green alga in aerobic bacteria evenly distributed
  • exposed alga to range of wavelengths 
  • bacteria found to cluster at blue and red wavelengths 
  • these had increased rates of photosynthesis 

structure and role of chloroplasts

  • organelles surrounded by a double membrane 
  • grana are stacks of disc like thylakoids with photosynthetic pigments
  • stroma is the fluid interior

photosynthetic pigments

  • light energy trapped 
  • different wavelengths trapped by different pigments
  • chlorophylls absorb in the red and blue regions 
  • carotenoids absorb from just the blue region
  • two main types of carotenoids are carotenes and xanthophylls which act as accessory pigments 

absorption and action spectra

  • absorption spectrum represents as a graph indicating how much light a particular pigment absorbs at each wavelength
  • action spectrum is a graph showing the rate of photosynthesis at different wavelengths
  • there is a close correlation between absorption spectrum and action spectrum
  • pigments are responsible for absorbing light used in photosynthesis

light harvesting

  • chlorophylls and accessory pigments in thylakoid membranes of chloroplast are grouped in clusters called antenna complex
  • proteins associated aid funneling photons of light so the pigments pass absorbed light energy from one to the next
  • tranferred until they reach chlorophyll a, a primary pigment molecule known as the reaction centre
  • photosystem 1 has absorption peak of 700nm
  • photosystem 2 has absorption peak of 680nm

light dependant stage of photosynthesis

  • occurs in thylakoid membranes
  • photolysis is the splitting of water by light producting H+ and e-
  • ATP is synthesised from ADP and Pi in photophosphorylation
  • H+ reduces NADP to NADPH
  • as electrons flow through chain of carriers


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