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Photosynthesis: Light Reactions and Calvin Cycle

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Terms in this set (14)

  • Where do the light reactions of photosynthesis occur?
    In the thylakoid membrane of the chloroplast.
  • What are the main inputs and outputs of the light reactions?
    Inputs: Light energy and H₂O. Outputs: ATP, NADPH, and O₂ (by-product).
  • What is the role of Photosystem II in the light reactions?
    Photosystem II absorbs light, energizes electrons, and splits water to replace electrons, releasing O₂ and H⁺.
  • What happens to electrons after Photosystem II?
    Electrons pass down an electron transport chain, pumping H⁺ into the thylakoid space.
  • What is the function of Photosystem I?
    Photosystem I re-energizes electrons before they reduce NADP⁺ to NADPH.
  • How is ATP produced in the light reactions?
    H⁺ flows back through ATP synthase via chemiosmosis, producing ATP.
  • Where does the Calvin cycle take place?
    In the stroma of the chloroplast.
  • What is the first step of the Calvin cycle?
    Carbon fixation: Rubisco attaches CO₂ to RuBP, forming two 3-carbon 3-PGA molecules.
  • What happens during the reduction phase of the Calvin cycle?
    ATP and NADPH convert 3-PGA into G3P, a 3-carbon sugar.
  • What is the regeneration step in the Calvin cycle?
    Most G3P is rearranged, using ATP, back into RuBP so the cycle can repeat.
  • How many G3P molecules are produced from 3 CO₂ in the Calvin cycle?
    6 G3P molecules are made; 1 G3P exits to make sugars, and 5 regenerate 3 RuBP.
  • What sugars are produced from G3P?
    G3P is converted into glucose, sucrose, and starch.
  • What is the relationship between light reactions and the Calvin cycle?
    Light reactions convert light energy into chemical energy (ATP, NADPH), which powers the Calvin cycle to store energy in organic molecules.
  • What is the overall chemical equation for photosynthesis?
    6 CO₂ + 6 H₂O + light → C₆H₁₂O₆ + 6 O₂.