What is "chlorophyll b"

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 dark-green plant pigment having a brilliant green alcohol solution

Chlorophyll b is a form of chlorophyll. Chlorophyll b helps in photosynthesis by absorbing light energy. It is more soluble than chlorophyll a in polar solvents because of its carbonyl group. Its color is yellow, and it primarily absorbs blue light.

In land plants, the light-harvesting antennae around photosystem II contain the majority of chlorophyll b. Hence, in shade-adapted chloroplasts, which have an increased ratio of photosystem II to photosystem I, there is a higher ratio of chlorophyll b to chlorophyll a. This is adaptive, as increasing chlorophyll b increases the range of wavelengths absorbed by the shade chloroplasts.

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Structure of chlorophyll b molecule showing the long hydrocarbon tail