}

Chlorophyll ''b'' is a form of

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to ...

. Chlorophyll ''b'' helps in

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...

by absorbing light energy. It is more soluble than chlorophyll ''a'' in

polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates *Polar climate, the cli ...

solvents because of its

carbonyl In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containi ...

group. Its color is green, and it primarily absorbs blue light. In

land plant The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as sist ...

s, 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 Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is located in the thylakoid membrane of plants, algae, and cyanobacteria. Within the photosyst ...

photosystem I Photosystem I (PSI, or plastocyanin–ferredoxin oxidoreductase) is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria. Photosystem I is an integral membrane protein complex that us ...

, 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.

Biosynthesis

The Chlorophyll ''b''

biosynthetic pathway Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...

utilizes a variety of

enzymes Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. ...

. In most plants, chlorophyll is derived from

glutamate Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can synt ...

and is synthesised along a branched pathway that is shared with

heme Heme, or haem (pronounced / hi:m/ ), is a precursor to hemoglobin, which is necessary to bind oxygen in the bloodstream. Heme is biosynthesized in both the bone marrow and the liver. In biochemical terms, heme is a coordination complex "consis ...

and

siroheme Siroheme (or sirohaem) is a heme-like prosthetic group at the active sites of some enzymes to accomplish the six-electron reduction of sulfur and nitrogen. It is a cofactor at the active site of sulfite reductase, which plays a major role in su ...

. The initial steps incorporate glutamic acid into

5-aminolevulinic acid δ-Aminolevulinic acid (also dALA, δ-ALA, 5ALA or 5-aminolevulinic acid), an endogenous non-proteinogenic amino acid, is the first compound in the porphyrin synthesis pathway, the pathway that leads to heme in mammals, as well as chlorophyll in p ...

(ALA); two molecules of ALA are then reduced to porphobilinogen (PBG), and four molecules of PBG are coupled, forming

protoporphyrin Protoporphyrin IX is an organic compound, classified as a porphyrin, that plays an important role in living organisms as a precursor to other critical compounds like heme ( hemoglobin) and chlorophyll. It is a deeply colored solid that is not s ...

IX.

Chlorophyll synthase In enzymology, chlorophyll synthase () is an enzyme that catalyzes the chemical reaction :chlorophyllide a + phytyl diphosphate \rightleftharpoons chlorophyll a + diphosphate The two substrates of this enzyme are chlorophyllide ''a'' and phyt ...

is the enzyme that completes the biosynthesis of chlorophyll ''b'' by catalysing the reaction :chlorophyllide ''b'' + phytyl diphosphate

\rightleftharpoons

chlorophyll ''b'' + diphosphate This forms an ester of the carboxylic acid group in chlorophyllide ''b'' with the 20-carbon

diterpene Diterpenes are a class of chemical compounds composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being ...

alcohol phytol.

References

{{DEFAULTSORT:Chlorophyll B Tetrapyrroles Photosynthetic pigments