Photosynthesis is divided into two main stages:
1. Light-Dependent Reactions (Light Reactions):
* Starting molecule: Light energy, water (H₂O)
* Ending molecules: ATP (adenosine triphosphate), NADPH (nicotinamide adenine dinucleotide phosphate), oxygen (O₂)
2. Light-Independent Reactions (Calvin Cycle):
* Starting molecule: Carbon dioxide (CO₂), ATP, NADPH
* Ending molecule: Glucose (C₆H₁₂O₆)
Summary of Stages:
Light-Dependent Reactions:
* Location: Thylakoid membranes of chloroplasts
* Key events:
* Light energy is absorbed by chlorophyll and other pigments.
* This energy excites electrons, driving the production of ATP and NADPH.
* Water molecules are split, releasing oxygen as a byproduct.
Light-Independent Reactions (Calvin Cycle):
* Location: Stroma of chloroplasts
* Key events:
* Carbon dioxide is incorporated into organic molecules (carbon fixation).
* ATP and NADPH from the light reactions provide energy to convert carbon dioxide into glucose.
* The cycle regenerates its starting molecules to continue the process.
Overall Reaction:
6CO₂ + 6H₂O + Light Energy → C₆H₁₂O₆ + 6O₂
This equation summarizes the overall process of photosynthesis, where carbon dioxide and water are converted into glucose and oxygen using light energy.
