Rucete ✏ Campbell Biology In a Nutshell
Unit 2 THE CELL — Concept 10.6 Photosynthesis Is Essential for Life on Earth: A Review
Photosynthesis captures light energy and stores it as chemical energy in sugars, fueling life on Earth. This process powers plant metabolism and supports ecosystems globally.
Photosynthesis in Context
- Combines light reactions and the Calvin cycle
- Light reactions convert solar energy to ATP and NADPH
- Calvin cycle uses ATP and NADPH to fix CO₂ into G3P (a sugar)
- Occurs in chloroplasts—light reactions in thylakoids, Calvin cycle in stroma
Fate of Photosynthetic Products
- G3P is used to build a variety of organic molecules
- Sugars provide energy and raw materials for respiration and biosynthesis
- Sugars are exported as sucrose to non-photosynthetic tissues
- Starch is stored in chloroplasts or organs like roots and seeds
- Glucose is also used to make cellulose for cell walls
Photosynthesis and Global Life
- Generates atmospheric O₂ for aerobic organisms
- Produces ~150 billion metric tons of carbohydrates annually
- Plants provide food and oxygen to nearly all organisms
- Green tissues are autotrophic; other plant parts rely on them
In a Nutshell
Photosynthesis converts sunlight into chemical energy, supporting plant growth and fueling nearly all ecosystems. It produces oxygen and organic compounds that sustain life on a global scale.