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natural-science

How Photosynthesis Works

A leaf is a tiny solar-powered workshop that builds sugar from air and water.

Think of a kitchen that receives water and carbon dioxide as ingredients. Sunlight powers the tools, sugar is the stored food, and oxygen leaves as a by-product.

  1. Water moving from soil through roots and upward into a green leaf.Water in soilRootsLeaf

    Step 1

    Roots bring in water

    Roots absorb water from the soil, and tubes in the plant carry it up to the leaves.

  2. Carbon dioxide passing through tiny stomata openings into a leaf.Tiny adjustabledoors=Stomata

    Step 2

    Leaves take in carbon dioxide

    Tiny openings called stomata let carbon dioxide from the air enter the leaf.

  3. Sunlight entering a leaf and being absorbed by chlorophyll inside chloroplasts.LeafPlant cellChloroplastChlorophyll

    Step 3

    Chlorophyll catches light

    Inside chloroplasts, the green pigment chlorophyll absorbs light energy, especially red and blue light.

  4. Light energy helping split water, release oxygen, and charge energy carriers.LightWater splitsEnergy carriersOxygen leaves

    Step 4

    Light starts the energy work

    Light-powered reactions split water, release oxygen, and load small energy-carrying molecules.

  5. Carbon dioxide and captured energy joining to form a sugar molecule.Carbon dioxideCalvin cycleSugar

    Step 5

    Carbon becomes sugar

    The Calvin cycle uses carbon dioxide and captured energy to assemble carbon-based sugar molecules.

  6. Plant-made sugar branching toward immediate energy, growth, and storage.Use nowRelease energyBuild new cellsSave for laterStore as starchMove to otherparts

    Step 6

    The plant uses and stores it

    The plant uses sugar for energy and building material, or links sugars together for later.

Common trap

Plants get all of their food from soil.

Soil supplies water and minerals. Plants build most of their dry material from carbon dioxide using energy from light.

Quick check

Where does the carbon in a plant's sugar come from?

  1. Carbon dioxide in the air
  2. Sunlight itself
  3. Oxygen in the soil
Show the answer

Photosynthesis uses carbon dioxide as the carbon source for building sugars.

Sources

  1. PhotosynthesisNational Geographic Education
  2. The Carbon Cycle: The Fast Carbon CycleNASA Earth Observatory