What is "chlorophyll a"

Chlorophyll \Chlo"ro*phyll\, n. [Gr. chlwro`s light green + fy`llon leaf: cf. F. chlorophylle.]

1. (Bot.) Literally, leaf green; a green granular matter formed in the cells of the leaves (and other parts exposed to light) of plants, to which they owe their green color, and through which all ordinary assimilation of plant food takes place. Similar chlorophyll granules have been found in the tissues of the lower animals. [Written also chlorophyl.]

2. any of a group of green pigments found in photosynthetic organisms. Chlorophyll a and chlorophyll b are found in higher plants and green algae; chlorophyll c is found in certain types of marine algae. Chemically, it has a porphyrin ring with a magnesium ion bound to the four central nitrogens, and has a phytyl side chain. It is essential for photosynthesis in most plants. Chlorophyll a has formula C55H72N4O5Mg.

   Syn: chlorophyll.

n. a blue-black plant pigment having a blue-green alcohol solution

Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light. It also reflects green/yellow light, and as such contributes to the observed green color of most plants. This photosynthetic pigment is essential for photosynthesis in eukaryotes, cyanobacteria and prochlorophytes because of its role as primary electron donor in the electron transport chain. Chlorophyll a also transfers resonance energy in the antenna complex, ending in the reaction center where specific chlorophylls P680 and P700 are located.

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Structure of Chlorophyll a molecule showing the long hydrocarbon tail