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.