Names | |
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IUPAC name
Chlorophyll b
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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
β-Chlorophyll
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Identifiers | |
3D model (
JSmol)
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ChemSpider | |
ECHA InfoCard | 100.007.522 |
EC Number |
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E number | E140 (colours) |
PubChem
CID
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UNII | |
CompTox Dashboard (
EPA)
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Properties | |
C55H70MgN4O6 | |
Molar mass | 907.492 g·mol−1 |
Appearance | Green |
Odor | Odorless |
Melting point | ~ 125 °C (257 °F; 398 K) [1] |
Insoluble [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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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 green, and it primarily absorbs blue light. [2]
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] 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 |
The Chlorophyll b biosynthetic pathway utilizes a variety of enzymes. [4] In most plants, chlorophyll is derived from glutamate and is synthesised along a branched pathway that is shared with heme and siroheme. [5] [6] [7] The initial steps incorporate glutamic acid into 5-aminolevulinic acid (ALA); two molecules of ALA are then reduced to porphobilinogen (PBG), and four molecules of PBG are coupled, forming protoporphyrin IX.
Chlorophyll synthase [8] is the enzyme that completes the biosynthesis of chlorophyll b [9] [10] by catalysing the reaction EC 2.5.1.62
This forms an ester of the carboxylic acid group in chlorophyllide b with the 20-carbon diterpene alcohol phytol.