Chlorophyll gives leaves their green color

Chlorophyll is found in high concentrations in chloroplasts of plant cells. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis.

SeaWIFS-derived average sea surface chlorophyll for the period 1998 to 2006.

Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria. For the drug referred to as "pigment" see Black tar heroin. Plants are living Organisms belonging to the kingdom Plantae. Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of Bacteria that obtain their energy Its name is derived from Greek: chloros = green and phyllon = leaf. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Green is a Color, the perception of which is evoked by light having a spectrum dominated by energy with a Wavelength of roughly 520–570- nm. In Botany, a leaf is an above-ground Plant organ specialized for Photosynthesis. Chlorophyll absorbs light most strongly in the blue and red but poorly in the green portions of the electromagnetic spectrum, hence the green color of chlorophyll-containing tissues like plant leaves. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies ^[1]

Chlorophyll and photosynthesis

Chlorophyll is vital for photosynthesis, which allows plants to obtain energy from light. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy.

Chlorophyll molecules are specifically arranged in and around pigment protein complexes called photosystems which are embedded in the thylakoid membranes of chloroplasts. Photosystems (ancient Greek: phos = light and systema = assembly are Protein complexes involved in Photosynthesis. A Thylakoid is a membrane-bound compartment inside Chloroplasts and cyanobacteria. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. In these complexes, chlorophyll serves two primary functions. The function of the vast majority of chlorophyll (up to several hundred 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. Förster resonance energy transfer (abbreviated FRET) also known as Fluoresence resonance energy transfer or resonance energy transfer ( RET A photosynthetic reaction center is a complex of three types of protein that is the site where molecular excitations originating from sunlight are transformed into a series of electron-transfer Because of chlorophyll’s selectivity regarding the wavelength of light it absorbs, areas of a leaf containing the molecule will appear green.

There are currently two accepted photosystem units, Photosystem II and Photosystem I, which have their own distinct reaction center chlorophylls, named P680 and P700, respectively. ^[2] These pigments are named after the wavelength (in nanometers) of their red-peak absorption maximum. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a 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 in a simple paper chromatography experiment, and, based on the number of polar groups between chlorophyll a and chlorophyll b, will chemically separate out on the paper. Acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and β-ketopropane) is a colorless mobile flammable Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a Chemical compound

The function of the reaction center chlorophyll is to use the energy absorbed by and transferred to it from the other chlorophyll pigments in the photosystems to undergo a charge separation, a specific redox reaction in which the chlorophyll donates an electron into a series of molecular intermediates called an electron transport chain. Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J An electron transport chain couples a chemical reaction between an electron donor (such as NADH) and an electron acceptor (such as O2) to the transfer The charged reaction center chlorophyll (P680⁺) is then reduced back to its ground state by accepting an electron. In Photosystem II, the electron which reduces P680⁺ ultimately comes from the oxidation of water into O₂ and H⁺ through several intermediates. This reaction is how photosynthetic organisms like 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, via many intermediates in the thylakoid membrane, by electrons 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 shuttle H⁺ ions across the thylakoid membrane, setting up a chemiosmotic potential mainly used to produce ATP chemical energy, and those electrons ultimately reduce NADP⁺ to NADPH a universal reductant used to reduce CO₂ into sugars as well as for other biosynthetic reductions. Chemiosmosis is the diffusion of Ions across a selectively-permeable membrane Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy Nicotinamide adenine dinucleotide phosphate ( NADP+, in older notation triphosphopyridine nucleotide TPN) is used in anabolic reactions such as Lipid Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state

Reaction center chlorophyll-protein complexes are capable of directly absorbing light and performing charge separation events without other chlorophyll pigments, but the absorption cross section (the likelihood of absorbing a photon under a given light intensity) is small. Thus, the remaining chlorophylls in the photosystem and antenna pigment protein complexes associated with the photosystems 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. Accessory pigments are light-absorbing compounds found in Photosynthetic Organisms that work in conjunction with Chlorophyll a.

Chemical structure

Space-filling model of the chlorophyll a molecule

Chlorophyll is a chlorin pigment, which is structurally similar to and produced through the same metabolic pathway as other porphyrin pigments such as heme. In Organic chemistry, a chlorin is a large Heterocyclic Aromatic ring consisting at the core of three Pyrroles and one Pyrroline A porphyrin is a heterocyclic Macrocycle derived from four Pyrroline subunits interconnected via their α carbon atoms via Methine bridges (=CH- A heme ( American English) or haem ( British English) is a Prosthetic group that consists of an Iron atom contained in the center of At the center of the chlorin ring is a magnesium ion. Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 The chlorin ring can have several different side chains, usually including a long phytol chain. Phytol is a natural linear diterpene Alcohol which is used in the preparation of vitamins E and K1 There are a few different forms that occur naturally, but the most widely distributed form in terrestrial plants is chlorophyll a. The general structure of chlorophyll a was elucidated by Hans Fischer in 1940, and by 1960, when most of the stereochemistry of chlorophyll a was known, Robert Burns Woodward published a total synthesis of the molecule as then known. Hans Fischer ( July 27, 1881 &ndash March 31, 1945) was a German organic chemist and the recipient of the 1930 Robert Burns Woodward ( April 10 1917 &ndash July 8 1979) was an American organic chemist. ^[3] In 1967, the last remaining stereochemical elucidation was completed by Ian Fleming,^[4] and in 1990 Woodward and co-authors published an updated synthesis. Ian Fleming (1935 – present is an English organic chemist and an Emeritus professor of the University of Cambridge. ^[5]

The different structures of chlorophyll are summarized below:

Structure of chlorophyll a	Structure of chlorophyll b	Structure of chlorophyll d
Structure of chlorophyll c1	Structure of chlorophyll c2

When leaves degreen in the process of plant senescence chlorophyll is converted to a group of colorless tetrapyrroles known as nonfluorescent chlorophyll catabolites (NCC's) with the general structure:

These compounds have also been identified in several ripening fruits. Plant senescence is the study of aging in plants It is a heavily studied subject just as it is in the other kingdoms of life Tetrapyrroles are compounds containing four Pyrrole rings With the exception of Corrin, the four pyrrole rings are interconnected through one-carbon ( Methine ^[6]

Spectrophotometry

Absorbance spectra of free chlorophyll a (green) and b (red) in a solvent. In Spectroscopy, the absorbance A is defined as A_\lambda = -\log_{10}(I/I_0\ where I is the intensity of light The spectra of chlorophyll molecules are slightly modified in vivo depending on specific pigment-protein interactions.

Measurement of the absorption of light is complicated by the solvent used to extract it 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. ^[7]
• The absorption peaks of Chlorophyll a are at 665 nm and 465 nm. Chlorophyll a fluoresces at 673 nm. The peak molar absorption coefficient of chlorophyll a exceeds 10⁵ M⁻¹ cm⁻¹, which is among the highest for organic compounds. The molar extinction coefficient, also known as molar absorptivity, is a measurement of how strongly a Chemical species absorbs light at a given

Biosynthesis

Further information: Chlorosis

In plants, chlorophyll may be synthesized from succinyl-CoA and glycine, although the immediate precursor to chlorophyll a and b is protochlorophyll. In Botany, chlorosis is a condition in which leaves produce insufficient Chlorophyll. Plants are living Organisms belonging to the kingdom Plantae. Succinyl-Coenzyme A, generally abbreviated as Succinyl-CoA or SucCoA is a combination of Succinic acid and Coenzyme A. Glycine (abbreviated as Gly or G) is the Organic compound with the formula NH2CH2COOH

Chlorosis is a condition in which leaves produce insufficient chlorophyll, turning them yellow. In Botany, a leaf is an above-ground Plant organ specialized for Photosynthesis. Chlorosis can be caused by a nutrient deficiency including iron - called iron chlorosis, or in a shortage of magnesium or nitrogen. Iron (Fe deficiency is a plant disorder also known as ‘lime-induced chlorosis’ Magnesium (Mg deficiency is a plant disorder with two main causes This is about nitrogen compounds in plant nutrition For shortage of nitrogen compounds in human and animal nutrition see Protein deficiency. Soil pH sometimes play a role in nutrient-caused chlorosis, many plants are adapted to grow in soils with specific pHs and their ability to absorb nutrients from the soil can be dependent on the soil pH. ^[8] Chlorosis can also be caused by pathogens including viruses, bacteria and fungal infections or sap sucking insects.

Culinary Use

Chefs use chlorophyll to color in green various dishes, such as pasta. Chlorophyll is not soluble in water and is first mixed with a small quantity of oil to obtain the desired result.

See also

• Bacteriochlorophyll, related compounds in phototrophic bacteria
• Chlorophyllin, a semi-synthetic derivative of chlorophyll
• Grow light, a lamp that promotes photosynthesis

References

External links

• Oregon University of Health & Sciences
• PDF review-Chlorophyll d: the puzzle resolved
• Light Absorption by Chlorophyll – NIH books