Chlorophyll

Chlorophyll is a family of green pigments found in plants, algae, and cyanobacteria. Its molecules absorb light energy used in photosynthesis.

Light-harvesting complex: A protein–pigment assembly that absorbs light and transfers excitation energy to a photosynthetic reaction center. Chlorophyll molecules are organized in these complexes, which funnel absorbed energy toward reaction centers.
Porphyrin: A class of large, ring-shaped molecules built from four linked nitrogen-containing subunits. Chlorophyll’s light-absorbing head has a related tetrapyrrole ring structure.
Photosynthesis: The process by which organisms convert light energy into chemical energy, commonly using carbon dioxide and water to form organic matter. Chlorophyll supplies the light absorption that drives oxygenic photosynthesis.
Bacteriochlorophyll: A family of light-absorbing pigments used by many anoxygenic photosynthetic bacteria. It resembles chlorophyll but supports photosynthesis that does not release oxygen.
Photosystem II: A photosynthetic protein complex that uses light energy to extract electrons from water. Its reaction-center chlorophyll initiates electron transfer and water oxidation.
Magnesium: A chemical element whose ions serve as cofactors in many biological molecules and enzymes. A magnesium ion sits at the center of chlorophyll’s tetrapyrrole ring.
Chlorophyll fluorescence: Light emitted by chlorophyll after absorption when excitation energy is not used for photochemistry or dissipated as heat. Fluorescence measurements reveal how efficiently photosynthetic machinery uses absorbed light.
Phycobilin: A water-soluble pigment family in cyanobacteria and red algae that transfers absorbed light energy to chlorophyll. These accessory pigments capture wavelengths chlorophyll absorbs poorly, especially in aquatic environments.
Photosystem I: A photosynthetic protein complex that uses light energy to help reduce NADP⁺ to NADPH. Its chlorophyll absorbs light that re-energizes electrons arriving from the photosynthetic electron transport chain.
Phytol: A long, hydrophobic alcohol chain found as a component of chlorophyll and vitamin E. This tail helps anchor chlorophyll within photosynthetic membranes and protein complexes.

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