The main purpose of the light-dependent reactions is to capture energy from sunlight and convert it into chemical energy in the form of ATP and NADPH, while releasing oxygen from the splitting of water.

Quick Scoop

  • The light-dependent reactions occur in the thylakoid membranes of the chloroplast, where chlorophyll absorbs light.
  • That absorbed light energy is used to split water (photolysis), producing electrons, protons, and oxygen gas as a byproduct.
  • The electrons move through an electron transport chain to generate ATP , and are finally used to reduce NADP⁺ to NADPH.
  • ATP and NADPH are then used in the Calvin cycle (light-independent reactions) to power the synthesis of sugars from carbon dioxide.

In short: light-dependent reactions turn sunlight and water into ATP, NADPH, and oxygen, providing the energy and reducing power for the next stage of photosynthesis.

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