Photosynthesis

Trapping energy to sustain life

Photosynthesis is the process by which plants (and other producers) take in raw materials — light energy, water, and carbon dioxide — and trap and store that energy as food, in the chloroplasts. It's the foundation of almost every food chain on Earth.

What photosynthesis needs

• Light — provides the energy that drives the reaction.
• Chlorophyll — the green pigment in chloroplasts that absorbs light energy.
• Carbon dioxide — taken in from the atmosphere, provides the carbon used to build glucose.
• Water — taken up by the roots.

The process happens in two linked phases — a light phase and a dark (light-independent) phase — but the biochemical detail of each isn't needed at this level; it's enough to know both are required.

What photosynthesis produces

• Oxygen — released as a by-product, essential for most life on Earth.
• Starch — glucose is often converted to starch for storage in the plant.

Why photosynthesis matters

Photosynthesis releases the oxygen almost all organisms need for respiration, removes carbon dioxide from the atmosphere, and produces the food that directly or indirectly feeds nearly every other organism on Earth.