chloroplasts and photosynthetic pigments

• NADP 


  • enzyme used in photosynthesis
  • transfers hydrogen from one molecule to another
• Light-dependent stage 


  • converts solar energy to chemical energy
  • photosynthesis occurs in thylakoid membrane
  • ATP made from ADP and inorganic phosphate group - Requires energy
  • adding phosphate - phosphorylation
  • light used for phosphorylation - photophosphorylation
• chloroplast structure

  • contains stroma, a fluid containing enzymes which catalyse reactions of the light - independent stage
  • Grana, stack of thylakoids
  • surrounded by double membrane
  • intermembrane space between inner and outer membrane - 10-20nm wide.
  • outer membrane is permeable to small ions
  • inner membrane less permeable but has transporter proteins embedded - folded into lamallae (thin plates) - stacked.
  • Each stack of lamallae is called a granum.
• photosynthetic pigments

  • trap sunlight energy
  • allow maximum absorption of light
• photosynthetic pigments 


  • in plants there are 2 types: chlorophyll and carotenoids. They are coloured because they absorb particular wavelengths of light and reflect others
  • chlorophyll is the pigment that make plants green - reflects green light
  • carotenoids reflect red, orange or yellow light
• chloroplast pigments 


  absorb light mainly in red and blue areas:

  • chlorophyll a
  • chlorophyll b

  carotenoids - energy absorbed eventually passed to chlorophyll
• • two forms of chlorophyll a - with slightly different absorption peaks (680nm and 700nm) - photosynthesis at its peak
• • thylakoid membranes contain many light harvesting pigment molecules arranged in funnel shapes called 'antennae complexes'
  • pigments allow it to be harvested across a greater range of spectrum, ending at reaction center
• Antenna complex

  
• thylakoid membrane

  
• chloroplast structure

  
• 1. photosystem II 680nm
  2. photosystem I 700nm
• NADP hydrolysed to form NADPH
• chlorophyll a - primary pigment reaction centre


  • as light hits accessory pigments which absorb the light they become excited and a pair of electrons are passed through pigments and through to primary pigment (chlorophyll a)