light-dependent

• light-dependent stage?

  energy from sunlight is absorbed and used to form ATP. Hydrogen from water is used to reduce NADP.
• in the thylakoid
• what are the stages of the light dependent reaction?

  photoexcitation, photolysis of water, phosphorylation, reduction
• what happens in photoexitation?

  energy from sunlight causes electrons from chlorophyll to become excited and leave the thylakoid
• what happens in the photolysis of water?

  splitting of water into H+ and e- and oxygen. the electrons replace those lost as a waste gas
• what happens in photophosphorylation?

  excited electrons are passed through a series of electron carriers and are used to produce ATP according to chemiosmosis. the ATP is then used in the LIR.
• what happens is reduction?

  the hydrogen ions are used to reduce NADP to NADPH
• what happens at photosystem II?

  1. light absorption (photoexcitation)
  2. splitting of water and releasing oxygen (a waste product)
  3. electron capture by the electron acceptor
• what happens at photosystem I?

  1. ETC - electrons are passed through the chain to photosystem I. the chain provides energy for the proton gradient needed in the calvin cycle
  2. enter photosystem I
  3. NADPH oxidised to NADP
• what is non-cyclic photophosphorylation?

  makes ATP to NADPH

  1. primary pigment is chlorophyll A. the accessory pigments absorb the light and pass energy to the primary pigment which releases the excited electrons
  2. electrons from photolysis of water replace those lost by chlorophyll. the hydrogen ions reduce the NADP.
  3. photophosphorylation
  4. reduced NADP
• what is cyclic phosphorylation?

  only makes ATP

  only photosystem I involved

  electrons recycled
• what is phosphorylation?

  the addition of phosphate using light energy
• what are the four functions of light?

  1. excites electrons for photophosphorylation
  2. excites electrons for the reduction of NADP
  3. triggers the opening of the stomata
  4. initiates photolysis of water