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 these molecules to fix CO₂ into G3P (a sugar)
Occurs in chloroplasts—specifically, in thylakoids (light reactions) and stroma (Calvin cycle)
Fate of Photosynthetic Products
G3P from the Calvin cycle is used to build a wide range of organic molecules
Sugars provide energy and raw materials for cellular respiration and biosynthesis
In most plants, sugars are exported as sucrose to non-photosynthetic tissues
Starch is stored in chloroplasts or storage organs like roots and seeds
Glucose is also used to make cellulose, the major component of cell walls
Photosynthesis and Global Life
Generates atmospheric O₂—essential for aerobic respiration
Produces ~150 billion metric tons of carbohydrates per year
Plants supply food and oxygen to nearly all organisms, directly or indirectly
Green tissues are the only autotrophic parts of plants; all other tissues 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.