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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.[2]

Chlorophyll b
Structure of β-Chlorophyll
IUPAC name
Chlorophyll b
Systematic IUPAC name
Magnesium [methyl (3S,4S,21R)-14-ethyl-13-formyl-4,8,18-trimethyl-20-oxo-3-(3-oxo-3-{[(2E,7R,11R)-3,7,11,15-tetramethyl-2-hexadecen-1-yl]oxy}propyl)-9-vinyl-21-phorbinecarboxylatato(2-)-κ2N,N′]
Other names
3D model (JSmol)
ECHA InfoCard 100.007.522
EC Number 208-272-4
E number E140 (colours)
Molar mass 907.49 g·mol−1
Appearance Green
Odor Odorless
Melting point ~ 125 °C (257 °F; 398 K)[1]
Solubility Very soluble in ethanol, ether, pyridine
Soluble in methanol[1]
Absorbance See text
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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The absorption spectrum of both the chlorophyll a and the chlorophyll b pigments. The use of both together enhances the size of the absorption of light for producing energy.

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.[3][full citation needed] This is adaptive, as increasing chlorophyll b increases the range of wavelengths absorbed by the shade chloroplasts.

Structure of chlorophyll b molecule showing the long hydrocarbon tail


  1. ^ a b c Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0. 
  2. ^ "Photosynthesis pigments". 
  3. ^ Kitajima and Hogan 2003