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CHLOROPHYLL (also CHLOROPHYL) is any of several closely related green pigments found in cyanobacteria and the chloroplasts of algae and plants . Its name is derived from the Greek words χλωρός, _chloros_ ("green") and φύλλον, _phyllon_ ("leaf"). Chlorophyll is essential in photosynthesis , allowing plants to absorb energy from light.

Chlorophyll
Chlorophyll
absorbs light most strongly in the blue portion of the electromagnetic spectrum , followed by the red portion. Conversely, it is a poor absorber of green and near-green portions of the spectrum, which it reflects, producing the green color of chlorophyll-containing tissues. Chlorophyll
Chlorophyll
molecules are specifically arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts. Two types of chlorophyll exist in the photosystems of green plants: chlorophyll a and b.

Chlorophyll
Chlorophyll
was first isolated and named by Joseph Bienaimé Caventou and Pierre Joseph Pelletier in 1817.

CONTENTS

* 1 Photosynthesis
Photosynthesis
* 2 Chemical structure * 3 Measurement of chlorophyll content * 4 Biosynthesis * 5 Complementary light absorbance of anthocyanins with chlorophylls

* 6 Distribution * 7 Culinary use * 8 See also * 9 References

PHOTOSYNTHESIS

Absorption maxima of chlorophylls against the spectrum of white light . Chlorophyll
Chlorophyll
absorbs energy from light strongly at visible frequencies.

Chlorophyll
Chlorophyll
is vital for photosynthesis , which allows plants to absorb energy from light .

Chlorophyll
Chlorophyll
molecules are specifically arranged in and around photosystems that are embedded in the thylakoid membranes of chloroplasts . In these complexes, chlorophyll serves two primary functions. The function of the vast majority of chlorophyll (up to several hundred molecules per photosystem) is to absorb light and transfer that light energy by resonance energy transfer to a specific chlorophyll pair in the reaction center of the photosystems. The two currently accepted photosystem units are photosystem II and photosystem I , which have their own distinct reaction centres, named P680 and P700 , respectively. These centres are named after the wavelength (in nanometers ) of their red-peak absorption maximum. The identity, function and spectral properties of the types of chlorophyll in each photosystem are distinct and determined by each other and the protein structure surrounding them. Once extracted from the protein into a solvent (such as acetone or methanol ), these chlorophyll pigments can be separated into chlorophyll a and chlorophyll b .

The function of the reaction center of chlorophyll is to absorb light energy and transfer it to other parts of the photosystem. The absorbed energy of the photon is transferred to an electron in a process called charge separation. The removal of the electron from the chlorophyll is an oxidation reaction. The chlorophyll donates the high energy electron to a series of molecular intermediates called an electron transport chain . The charged reaction center of chlorophyll (P680+) is then reduced back to its ground state by accepting an electron stripped from water. The electron that reduces P680+ ultimately comes from the oxidation of water into O2 and H+ through several intermediates. This reaction is how photosynthetic organisms such as plants produce O2 gas, and is the source for practically all the O2 in Earth's atmosphere. Photosystem I typically works in series with Photosystem II; thus the P700+ of Photosystem I is usually reduced as it accepts the electron, via many intermediates in the thylakoid membrane, by electrons coming, ultimately, from Photosystem II. Electron transfer reactions in the thylakoid membranes are complex, however, and the source of electrons used to reduce P700+ can vary.

The electron flow produced by the reaction center chlorophyll pigments is used to pump H+ ions across the thylakoid membrane, setting up a chemiosmotic potential used mainly in the production of ATP (stored chemical energy) or to reduce NADP+ to NADPH
NADPH
. NADPH
NADPH
is a universal agent used to reduce CO2 into sugars as well as other biosynthetic reactions.

Reaction center chlorophyll–protein complexes are capable of directly absorbing light and performing charge separation events without the assistance of other chlorophyll pigments, but the probability of that happening under a given light intensity is small. Thus, the other chlorophylls in the photosystem and antenna pigment proteins all cooperatively absorb and funnel light energy to the reaction center. Besides chlorophyll _a_, there are other pigments, called accessory pigments , which occur in these pigment–protein antenna complexes.

CHEMICAL STRUCTURE

_ Space-filling model of the chlorophyll a_ molecule

Chlorophyll
Chlorophyll
is a chlorin pigment, which is structurally similar to and produced through the same metabolic pathway as other porphyrin pigments such as heme . At the center of the chlorin ring is a magnesium ion . This was discovered in 1906, and was the first time that magnesium had been detected in living tissue. For the structures depicted in this article, some of the ligands attached to the Mg2+ center are omitted for clarity. The chlorin ring can have several different side chains, usually including a long phytol chain. There are a few different forms that occur naturally, but the most widely distributed form in terrestrial plants is chlorophyll _a_. After initial work done by German chemist Richard Willstätter spanning from 1905 to 1915, the general structure of chlorophyll _a_ was elucidated by Hans Fischer in 1940. By 1960, when most of the stereochemistry of chlorophyll _a_ was known, Robert Burns Woodward published a total synthesis of the molecule. In 1967, the last remaining stereochemical elucidation was completed by Ian Fleming , and in 1990 Woodward and co-authors published an updated synthesis. Chlorophyll
Chlorophyll
f was announced to be present in cyanobacteria and other oxygenic microorganisms that form stromatolites in 2010; a molecular formula of C55H70O6N4Mg and a structure of (2-formyl )-chlorophyll _a_ were deduced based on NMR, optical and mass spectra. The different structures of chlorophyll are summarized below:

CHLOROPHYLL A CHLOROPHYLL B CHLOROPHYLL C1 CHLOROPHYLL C2 CHLOROPHYLL D CHLOROPHYLL F

Molecular formula C55H72O5N4Mg C55H70O6N4Mg C35H30O5N4Mg C35H28O5N4Mg C54H70O6N4Mg C55H70O6N4Mg

C2 group -CH3 -CH3 -CH3 -CH3 -CH3 -CHO

C3 group -CH=CH2 -CH=CH2 -CH=CH2 -CH=CH2 -CHO -CH=CH2

C7 group -CH3 -CHO -CH3 -CH3 -CH3 -CH3

C8 group -CH2CH3 -CH2CH3 -CH2CH3 -CH=CH2 -CH2CH3 -CH2CH3

C17 group -CH2CH2COO-Phytyl -CH2CH2COO-Phytyl -CH=CHCOOH -CH=CHCOOH -CH2CH2COO-Phytyl -CH2CH2COO-Phytyl

C17-C18 bond Single (chlorin) Single (chlorin) Double (porphyrin) Double (porphyrin) Single (chlorin) Single (chlorin)

Occurrence Universal Mostly plants Various algae Various algae Cyanobacteria Cyanobacteria

_ Structure of chlorophyll a_ _ Structure of chlorophyll b_ _ Structure of chlorophyll d_

_ Structure of chlorophyll c1_ _ Structure of chlorophyll c2_ _ Structure of chlorophyll f_

When leaves degreen in the process of plant senescence , chlorophyll is converted to a group of colourless tetrapyrroles known as NONFLUORESCENT CHLOROPHYLL CATABOLITES (NCC's) with the general structure:

These compounds have also been identified in several ripening fruits.

MEASUREMENT OF CHLOROPHYLL CONTENT

_ Absorbance spectra of free chlorophyll a_ (blue) and _b_ (red) in a solvent. The spectra of chlorophyll molecules are slightly modified _in vivo_ depending on specific pigment-protein interactions. Because it absorbs red and blue light strongly but is transparent to green light, pure chlorophyll has a strong green colour.

Measurement of the absorption of light is complicated by the solvent used to extract the chlorophyll from plant material, which affects the values obtained,

* In diethyl ether , chlorophyll _a_ has approximate absorbance maxima of 430 nm and 662 nm, while chlorophyll _b_ has approximate maxima of 453 nm and 642 nm. * The absorption peaks of chlorophyll _a_ are at 665 nm and 465 nm. Chlorophyll
Chlorophyll
_a_ fluoresces at 673 nm (maximum) and 726 nm. The peak molar absorption coefficient of chlorophyll _a_ exceeds 105 M−1 cm−1, which is among the highest for small-molecule organic compounds. * In 90% acetone-water, the peak absorption wavelengths of chlorophyll _a_ are 430 nm and 664 nm; peaks for chlorophyll _b_ are 460 nm and 647 nm; peaks for chlorophyll _c1_ are 442 nm and 630 nm; peaks for chlorophyll _c2_ are 444 nm and 630 nm; peaks for chlorophyll _d_ are 401 nm, 455 nm and 696 nm.

By measuring the absorption of light in the red and far red regions, it is possible to estimate the concentration of chlorophyll within a leaf.

Ratio fluorescence emission can be used to measure chlorophyll content. By exciting chlorophyll “a” fluorescence at a lower wavelength, the ratio of chlorophyll fluorescence emission at 705 nm +/- 10 nm and 735 nm +/-10 nm can provide a linear relationship of chlorophyll content when compared to chemical testing. The ratio F735/F700 provided a correlation value of r2 0.96 compared to chemical testing in the range from 41 mg m−2 up to 675 mg m−2. Gitelson also developed a formula for direct readout of chlorophyll content in mg m−2. The formula provided a reliable method of measuring chlorophyll content from 41 mg m−2 up to 675 mg m−2 with a correlation r2 value of 0.95.

BIOSYNTHESIS

Further information: Protochlorophyllide

In plants, chlorophyll may be synthesized from succinyl-CoA and glycine , although the immediate precursor to chlorophyll _a_ and _b_ is protochlorophyllide . In Angiosperm plants, the last step, the conversion of protochlorophyllide to chlorophyll, is light-dependent and such plants are pale (etiolated ) if grown in darkness. Non-vascular plants and green algae have an additional light-independent enzyme and grow green even in darkness.

Chlorophyll
Chlorophyll
itself is bound to proteins and can transfer the absorbed energy in the required direction. Protochlorophyllide occurs mostly in the free form and, under light conditions, acts as a photosensitizer , forming highly toxic free radicals . Hence, plants need an efficient mechanism of regulating the amount of chlorophyll precursor. In angiosperms, this is done at the step of aminolevulinic acid (ALA), one of the intermediate compounds in the biosynthesis pathway. Plants that are fed by ALA accumulate high and toxic levels of protochlorophyllide; so do the mutants with the damaged regulatory system. Further information: Chlorosis
Chlorosis

Chlorosis
Chlorosis
is a condition in which leaves produce insufficient chlorophyll, turning them yellow. Chlorosis
Chlorosis
can be caused by a nutrient deficiency of iron —called iron chlorosis—or by a shortage of magnesium or nitrogen . Soil pH sometimes plays a role in nutrient-caused chlorosis; many plants are adapted to grow in soils with specific pH levels and their ability to absorb nutrients from the soil can be dependent on this. Chlorosis
Chlorosis
can also be caused by pathogens including viruses, bacteria and fungal infections, or sap-sucking insects.

COMPLEMENTARY LIGHT ABSORBANCE OF ANTHOCYANINS WITH CHLOROPHYLLS

Superposition of spectra of chlorophyll a and b with oenin (malvidin 3O glucoside), a typical anthocyanidin , showing that, while chlorophylls absorb in the blue and yellow/red parts of the visible spectrum, oenin absorbs mainly in the green part of the spectrum, where chlorophylls don't absorb at all.

Anthocyanins are other plant pigments . The absorbance pattern responsible for the red color of anthocyanins may be complementary to that of green chlorophyll in photosynthetically active tissues such as young _ Quercus coccifera _ leaves. It may protect the leaves from attacks by plant eaters that may be attracted by green color.

DISTRIBUTION

Play media Animation depicting nearly four years worth of SeaWiFS
SeaWiFS
ocean chlorophyll concentration.

The chlorophyll maps show milligrams of chlorophyll per cubic meter of seawater each month. Places where chlorophyll amounts were very low, indicating very low numbers of phytoplankton , are blue. Places where chlorophyll concentrations were high, meaning many phytoplankton were growing, are yellow. The observations come from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite. Land is dark gray, and places where MODIS could not collect data because of sea ice, polar darkness, or clouds are light gray.The highest chlorophyll concentrations, where tiny surface-dwelling ocean plants are thriving , are in cold polar waters or in places where ocean currents bring cold water to the surface, such as around the equator and along the shores of continents. It is not the cold water itself that stimulates the phytoplankton. Instead, the cool temperatures are often a sign that the water has welled up to the surface from deeper in the ocean, carrying nutrients that have built up over time. In polar waters, nutrients accumulate in surface waters during the dark winter months when plants cannot grow. When sunlight returns in the spring and summer, the plants flourish in high concentrations.

CULINARY USE

Chlorophyll
Chlorophyll
is registered as a food additive (colorant), and its E number is E140. Chefs use chlorophyll to color a variety of foods and beverages green, such as pasta and absinthe . Chlorophyll
Chlorophyll
is not soluble in water, and it is first mixed with a small quantity of vegetable oil to obtain the desired solution .

SEE ALSO

_ Wikimedia Commons has media related to CHLOROPHYLL _.

* Bacteriochlorophyll , related compounds in phototrophic bacteria * Chlorophyll a
Chlorophyll a
, an essential chlorophyll pigment * Chlorophyll b
Chlorophyll b
, also an essential chlorophyll pigment * Chlorophyllin , a semi-synthetic derivative of chlorophyll * Deep chlorophyll maximum * Grow light , a lamp that promotes photosynthesis * Chlorophyll fluorescence , to measure plant stress

REFERENCES

* ^ May, Paul. "Chlorophyll". University of Bristol
University of Bristol
. * ^ "chlorophyll". Online Etymology Dictionary . * ^ Muneer, Sowbiya; Kim, Eun Jeong; Park, Jeong Suk; Lee, Jeong Hyun (2014-03-17). "Influence of Green, Red
Red
and Blue Light
Light
Emitting Diodes on Multiprotein Complex Proteins and Photosynthetic Activity under Different Light
Light
Intensities in Lettuce Leaves (Lactuca sativa L.)". _International Journal of Molecular Sciences_. 15 (3): 4657–4670. ISSN 1422-0067 . PMC 975419  _. PMID 24642884 . doi :10.3390/ijms15034657 . * ^ Speer, Brian R. (1997). "Photosynthetic Pigments". UCMP Glossary (online)_. University of California Museum of Paleontology . Retrieved 2010-07-17.

* ^ See:

* Delépine, Marcel (September 1951). "Joseph Pelletier and Joseph Caventou". _ Journal of Chemical Education _. 28 (9): 454. Bibcode :1951JChEd..28..454D. doi :10.1021/ed028p454 . * Pelletier and Caventou (1817) "Notice sur la matière verte des feuilles" (Notice on the green material in leaves), _Journal de Pharmacie_, 3 : 486-491. On p. 490, the authors propose a new name for chlorophyll. From p. 490: _"Nous n'avons aucun droit pour nommer une substance connue depuis long-temps, et à l'histoire de laquelle nous n'avons ajouté que quelques faits ; cependant nous proposerons, sans y mettre aucune importance, le nom de_ chlorophyle_, de_ chloros_, couleur, et_ φυλλον_, feuille : ce nom indiquerait le rôle qu'elle joue dans la nature."_ (We have no right to name a substance known for a long time, and to whose story we have added only a few facts ; however, we will propose, without giving it any importance, the name _chlorophyll_, from _chloros_, color, and _φυλλον_, leaf : this name would indicate the role that it plays in nature.)

* ^ Carter, J. Stein (1996). "Photosynthesis". University of Cincinnati . Archived from the original on 2013-06-29. * ^ Nature (July 5, 2013). "Unit 1.3. Photosynthetic Cells". _Essentials of Cell Biology_. nature.com. * ^ Marker, A. F. H. (1972). "The use of acetone and methanol in the estimation of chlorophyll in the presence of phaeophytin". _Freshwater Biology_. 2 (4): 361–385. doi :10.1111/j.1365-2427.1972.tb00377.x . * ^ Jeffrey, S. W.; Shibata, Kazuo (February 1969). "Some Spectral Characteristics of Chlorophyll c from Tridacna crocea Zooxanthellae". _ Biological Bulletin
Biological Bulletin
_. Marine Biological Laboratory . 136 (1): 54–62. JSTOR 1539668 . doi :10.2307/1539668 . * ^ Gilpin, Linda (21 March 2001). "Methods for analysis of benthic photosynthetic pigment". School of Life Sciences, Napier University . Archived from the original on April 14, 2008. Retrieved 2010-07-17. * ^ Willstätter, Richard (1906) "Zur Kenntniss der Zusammensetzung des Chlorophylls" ( to the knowledge of the composition of chlorophyll), _Annalen der Chemie_, 350 : 48-82. From p. 49: _"Das Hauptproduct der alkalischen Hydrolyse bilden tiefgrüne Alkalisalze. In ihnen liegen complexe Magnesiumverbindungen vor, die das Metall in einer gegen Alkali auch bei hoher Temperatur merkwürdig widerstandsfähigen Bindung enthalten."_ (Deep green alkali salts form the main product of alkali hydrolysis. In them, complex magnesium compounds are present, which contain the metal in a bond that's extraordinarily resistant to alkali even at high temperature.) * ^ _A_ _B_ Motilva, Maria-José (2008). "Chlorophylls – from functionality in food to health relevance". _5th Pigments in Food congress- for quality and health_ (Print). University of Helsinki. ISBN 978-952-10-4846-3 . * ^ Woodward, R. B.; Ayer, W. A.; Beaton, J. M.; Bickelhaupt, F.; Bonnett, R.; Buchschacher, P.; Closs, G. L.; Dutler, H.; Hannah, J.; et al. (July 1960). "The total synthesis of chlorophyll". _Journal of the American Chemical Society _. 82 (14): 3800–3802. doi :10.1021/ja01499a093 . * ^ Fleming, Ian (14 October 1967). "Absolute Configuration and the Structure of Chlorophyll". _Nature _. 216 (5111): 151–152. Bibcode :1967Natur.216..151F. doi :10.1038/216151a0 . * ^ Woodward, R. B.; Ayer, William A.; Beaton, John M.; Bickelhaupt, Friedrich; Bonnett, Raymond; Buchschacher, Paul; Closs, Gerhard L.; Dutler, Hans; Hannah, John; et al. (1990). "The total synthesis of chlorophyll a" (PDF). _Tetrahedron _. 46 (22): 7599–7659. doi :10.1016/0040-4020(90)80003-Z . * ^ Jabr, Ferris (August 19, 2010) A New Form of Chlorophyll?. _Scientific American_. Retrieved on 2012-04-15. * ^ Infrared chlorophyll could boost solar cells. New Scientist. August 19, 2010. Retrieved on 2012-04-15. * ^ Chen, Min; Schliep, Martin; Willows, Robert D.; Cai, Zheng-Li; Neilan, Brett A.; Scheer, Hugo (September 2010). "A Red-Shifted Chlorophyll". _Science _. 329 (5997): 1318–1319. Bibcode :2010Sci...329.1318C. PMID 20724585 . doi :10.1126/science.1191127 . * ^ Müller, Thomas; Ulrich, Markus; Ongania, Karl-Hans; Kräutler, Bernhard (2007). "Colorless Tetrapyrrolic Chlorophyll
Chlorophyll
Catabolites Found in Ripening Fruit
Fruit
Are Effective Antioxidants" . _Angewandte Chemie _. 46 (45): 8699–8702. PMC 2912502  _. PMID 17943948 . doi :10.1002/anie.200703587 . * ^ Gross, Jeana (1991). Pigments in vegetables: chlorophylls and carotenoids_. Van Nostrand Reinhold, ISBN 0442006578 . * ^ Porra, R. J. (1989). "Determination of accurate extinction coefficients and simultaneous equations for assaying chlorophylls a and b extracted with four different solvents: verification of the concentration of chlorophyll standards by atomic absorption spectroscopy". _Biochimica et Biophysica Acta (BBA) - Bioenergetics_. Volume 975 (3): 384, 394. doi :10.1016/S0005-2728(89)80347-0 – via Elsevier Science Direct. * ^ Larkum, edited by Anthony W. D. Larkum, Susan E. Douglas & John A. Raven (2003). _ Photosynthesis
Photosynthesis
in algae_. London: Kluwer. ISBN 0-7923-6333-7 . CS1 maint: Extra text: authors list (link ) * ^ Cate, Thomas; Perkins, T. D. (September 2003). "Joseph Pelletier and Joseph Caventou". _Journal of Tree
Tree
Physiology_. 23 (15): 1077–1079. doi :10.1093/treephys/23.15.1077 . * ^ Gitelson A. A., Buschmann C., Lichtenthaler H. K. (1999) “The Chlorophyll
Chlorophyll
Fluorescence Ratio F735/F700 as an Accurate Measure of Chlorophyll
Chlorophyll
Content in Plants” Remote Sens. Enviro. 69:296-302 (1999) * ^ Meskauskiene R; Nater M; Goslings D; Kessler F; op den Camp R; Apel K. (23 October 2001). "FLU: A negative regulator of chlorophyll biosynthesis in Arabidopsis thaliana" . _Proceedings of the National Academy of Sciences _. 98 (22): 12826–12831. Bibcode :2001PNAS...9812826M. JSTOR 3056990 . PMC 60138  _. PMID 11606728 . doi :10.1073/pnas.221252798 . * ^ Duble, Richard L. "Iron Chlorosis
Chlorosis
in Turfgrass". Texas A&M University . Retrieved 2010-07-17. * ^ Karageorgou, P.; Manetas, Y. (2006). "The importance of being red when young: Anthocyanins and the protection of young leaves of Quercus coccifera from insect herbivory and excess light". Tree Physiology_. 26 (5): 613–21. PMID 16452075 . doi :10.1093/treephys/26.5.613 . * ^ Chlorophyll
Chlorophyll
: Global Maps. Earthobservatory.nasa.gov. Retrieved on 2014-02-02. * ^ Adams, Jad (2004). _Hideous absinthe : a history of the devil in a bottle_. United Kingdom: I.B.Tauris, 2004. p. 22. ISBN 1860649203 .

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