light reactions

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Ginger

Cards (50)

  • Photosynthetic pigments

    Arranged as "photosystems"
  • Photosystems use some wavelengths of light but reflect others
  • Photosynthetic pigments

    Arranged as "photosystems"
  • Chlorophyll

    A pigment molecule that functions to capture (absorb) light energy
  • Chlorophyll doesn't capture light energy alone, it works with several hundred chlorophyll molecules and other pigments like carotenoids or xanthophylls
  • Photosystems use some wavelengths of light but reflect others
  • Light is trapped and absorbed by a network of chlorophyll pigments
  • Chlorophyll

    A pigment molecule that functions to capture (absorb) light energy
  • Chlorophyll doesn't capture light energy alone, it works with several hundred chlorophyll molecules and other pigments like carotenoids or xanthophylls
  • Photosystems

    1. Chlorophyll molecules absorb photons and raise their electrons to a higher energy level
    2. Excited electrons reduce a reaction center, the primary acceptor in a redox reaction
    3. This process is called photo-oxidation
  • Light is trapped and absorbed by a network of chlorophyll pigments
  • There exists 2 photosystems that function to gather light energy
  • Photosystems

    1. Chlorophyll molecules absorb photons and raise their electrons to a higher energy level
    2. Excited electrons reduce a reaction center, the primary acceptor in a redox reaction
    3. This process is called photo-oxidation
  • Robert Emerson determined that efficiency of photosynthesis greatly increased when he combined short and long wavelengths, concluding that two photosystems existed and photosynthesis worked best when both were operating
  • There exists 2 photosystems that function to gather light energy
  • Photosystem I and photosystem II
    The two light-capturing complexes used by most photoautotrophs
  • Robert Emerson determined that efficiency of photosynthesis greatly increased when he combined short and long wavelengths, concluding that two photosystems existed and photosynthesis worked best when both were operating
  • Photosystem I and photosystem II
    The two light-capturing complexes used by most photoautotrophs
  • The electron carriers of the photosynthetic system consist of non-protein organic groups that alternate between being oxidized and being reduced as electrons move through the system
  • The carriers include compounds that are similar in structure and function to those in mitochondrial electron transport chains
  • The electron carriers of the photosynthetic system consist of non-protein organic groups that alternate between being oxidized and being reduced as electrons move through the system
  • Light Harvesting Pigments

    Absorb light energy and transfer it to the Reaction Center
  • The carriers include compounds that are similar in structure and function to those in mitochondrial electron transport chains
  • Reaction Center

    Where the absorbed light energy is used to drive electron transport
  • Photosystems

    • Light Harvesting Pigments
    • Reaction Center
    • Photon
  • Photon

    A particle of light
  • Photosynthetic Electron Transport Chain (PETC)

    Electrons are passed along from the Photosystem
  • Photosystem

    The light-capturing complexes that contain the light harvesting pigments and reaction centers
  • Light Reactions

    1. Oxidation of P680
    2. Oxidation-reduction of plastoquinone
    3. Electron transfer from the cytochrome complex and shuttling by plastocyanin
    4. Oxidation-reduction of P700
    5. Electron transfer to NADP+ by ferredoxin
    6. Formation of NADPH
  • Photosynthetic Electron Transport Chain (PETC)

    Electrons are passed along from the Photosystem
  • The proton gradient is used to generate ATP with the same kind of ATP synthase complexes found in mitochondrial membranes
  • Light Reactions

    1. Oxidation of P680
    2. Oxidation-reduction of plastoquinone
    3. Electron transfer from the cytochrome complex and shuttling by plastocyanin
    4. Oxidation-reduction of P700
    5. Electron transfer to NADP+ by ferredoxin
    6. Formation of NADPH
  • Chemiosmotic Synthesis of ATP
    1. Protons are taken into the lumen by the reduction and oxidation of plastoquinone
    2. The concentration of protons inside the lumen is increased by the addition of two protons for each water molecule that is split in the lumen
    3. The removal of one proton from the stroma for each NADPH molecule formed decreases the concentration of protons in the stroma outside the thylakoid
  • The absorption of light energy by photosystem II results in the formation of an excited-state P680 (P680*) molecule, which is rapidly oxidized, transferring a high-energy electron to the primary acceptor
  • The higher concentration of protons inside the membrane creates a substantial proton-motive force that drives protons out of the lumen, back into the stroma
  • Oxidation-reduction of plastoquinone (PQ)

    1. PQ accepts electrons from photosystem II and also gains protons (H+) from the stroma
    2. When PQ donates electrons to the cytochrome complex, it also releases protons into the lumen, increasing the proton concentration there
  • The chloroplast's ATP synthase is identical to the ATP synthase used in cellular respiration
  • Cyclic Electron Flow

    1. Photosystem I can function independently of photosystem II
    2. Reduced ferredoxin donates electrons back to plastoquinone
    3. Plastoquinone gets continually reduced and oxidized, keeping protons moving across the thylakoid membrane without the involvement of photosystem II
  • Electron transfer from the cytochrome complex and shuttling by plastocyanin

    Electrons pass from the cytochrome complex to the mobile carrier plastocyanin, which shuttles electrons to photosystem I
  • The net result of cyclic electron transport is that the energy absorbed from light is converted into the chemical energy of ATP without the oxidation of water or the reduction of NADP+ to NADPH