photosynthesis

Introduction & Top Questions
Importance of photosynthesis
Evolution of the process
General characteristics
- Overall reaction of photosynthesis
- Basic products of photosynthesis
- Factors that influence the rate of photosynthesis
  - Light intensity and temperature
  - Carbon dioxide
  - Water
  - Minerals
  - Internal factors
- Energy efficiency of photosynthesis
Chloroplasts
- Structural features
- Chemical composition of lamellae
  - Lipids
  - Proteins
  - Quinones
- Genetics
The light reactions
- Step one: Light absorption and energy transfer
  - The pathway of electrons
  - Quantum requirements
- Step two: The conversion of light energy to ATP
The “dark reactions”: carbon fixation and reduction
- The Calvin-Benson cycle
  - Stage 1: Carboxylation
  - Stage 2: Reduction
  - Stage 3: Regeneration
  - Regulation of the cycle
  - Photorespiration
- Carbon fixation in C₄ plants
- Carbon fixation via crassulacean acid metabolism (CAM)
- Differences in carbon fixation pathways
- Products of the dark reactions
History of the study of photosynthesis
- Development of the idea
- Studies of chloroplasts
- Evidence of two light reactions
- Electron flow and ATP
- Elucidation of the carbon pathway
- Recent and contemporary research

References & Edit History Related Topics

Images & Videos

Learn How the Layered Arrangement of Chlorophyll Molecules Within a Leaf Increases Its Photosynthetic Output

The Relationship Between Photosynthesis and Breathing

The Process of Photosynthesis in Plants Explained

For Students

Photosynthesis diagram showing how water, light, and carbon dioxide are absorbed by a plant and that oxygen and sugars are produced. Also show a person to illustrate the oxygen/carbon dioxide cycle between plants and animals.

Pop Quiz: 13 Things to Know About Photosynthesis

photosynthesis summary

photosynthesis

biology

Written by

Hans LambersAll

Fact-checked by

Britannica Editors

Last updated

Nov. 30, 2025 •History

photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds. It would be impossible to overestimate the importance of photosynthesis in the maintenance of life on Earth. The Great Oxidation Event, which began about 2.4 billion years ago and was largely driven by the...

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