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Photosynthesis: Light Reactions Overview

Oct 14, 2024

Photosynthesis: Light Reactions and Calvin Cycle

Light Dependent Reactions

  • Location: Occur in the thylakoid, a part of the chloroplast.
  • Requirements: Sunlight, water, and chlorophyll.

Process of Light Dependent Reactions

  • Sunlight Absorption: Sunlight enters the thylakoid and is absorbed by chlorophyll.
  • Water Breakdown: Water is broken down into hydrogen and oxygen.
    • Oxygen is released into the atmosphere.
    • Hydrogen is carried away by NADP+, which becomes NADPH.

The Role of NADPH

  • NADPH Description:
    • Energy Carrier: Carries energy from light dependent reactions to light independent reactions.
    • Hydrogen Carrier: Carries hydrogen from water to the Calvin Cycle.

Light Independent Reactions (Calvin Cycle)

  • Location: Occur in the stroma, a fluid-filled region of the chloroplast.
  • Requirements: Does not require sunlight.

Process of Light Independent Reactions

  • Carbon Dioxide Entry: Carbon dioxide from the atmosphere enters the stroma.
  • Energy Supply: NADPH from light dependent reactions provides energy.
  • Carbon Fixation: Carbon dioxide is fixed into a glucose molecule through a series of reactions.
    • Definition: Carbon fixation converts low-energy, inorganic molecules into high-energy, organic molecules.

Calvin Cycle Steps

  1. Carbon Fixation: Carbon dioxide is converted into a glucose molecule.
  2. Energy Usage: Energy from NADPH is used to drive the process.
  3. Glucose Production: Glucose is produced and released into the plant.

Key Terms

  • Chlorophyll: A green pigment that absorbs sunlight.
  • Thylakoid: A part of the chloroplast where light dependent reactions occur.
  • Stroma: A fluid-filled region of the chloroplast where light independent reactions occur.
  • NADPH: A molecule that carries hydrogen and energy.
  • Calvin Cycle: A series of reactions in the stroma to produce glucose.