Algal pigments structure and function (2)

Algal Pigments - Structure and functions

1. Algal Pigments- Structure and Function Submitted By Moumita Paul Dept. of Life Science and Bioinformatics

2. INTRODUCTION Algae comprises the simplest plants which possess undifferentiated roots, stem and leaves or thallus Range in size from microscopic to single celled organisms to large seaweed Chlorophyll containing autotrophic members of thallopthyta Members of blue-green algae( Cyanophyta ) possess prokaryotic nature of cells, while the remaining algae to other division possess eukaryotic nature of cells Plastids(chloroplast or chromoplasts ) are present in the cytoplasm of each cell. One or more specialized bodies called pyrenoids which consists of colourless masses of proteins sourrounded by starch plates

3. ALGAL PIGMENTS Pigments are chemical compounds which reflect only certain wavelengths of visible light. This makes them appear "colourful". Flowers, corals, and even animal skin contain pigments which give them their colours. More important than their reflection of light is the ability of pigments to absorb certain wavelengths A photosynthetic pigment ( accessory pigment ; chloroplast pigment ; antenna pigment ) is a pigment that is present in chloroplasts of any photosynthetic organisn and captures the light energy necessary for photosynthesis Since each pigment reacts with only a narrow range of the spectrum, there is usually a need to produce several kinds of pigments, each of a different color , to capture more of the sun's energy. The pigments found in algae are Chlorophyll Xanthophyll Fucoxanthin Phycocyanin Phycoerythrin

4. CHLOROPHYLL Chlorophyll (also chlorophyl ) is a green pigment found in cyanobacteria and the chloroplasts of algae and plants Chlorophyll absorbs light most strongly in the blue portion of the electromagnetic spectrum, followed by the red portion . There are different types of Chlorophyll pigment that have been identified by famous chemists including Richard Willstätter , Hans Fischer, Robert Burns Woodward and Ian Fleming. Their structures are based on a chlorin ring at the center of which is a magnesium ion The structure can have different side chains depending on the type of Chlorophyll

5. CHOLROPHYLL a Chlorophyll a is the most widely occurring and universal type of Chlorophyll . Molecular formula - C 55 H 72 O 5 N 4 Mg Chlorophylls are greenish pigments which contain a porphyrin ring . Molecular structure consists of a chlorin ring with Mg center . The chlorin ring is a heterocyclic compound derived from pyrrole Four nitrogen atoms from the chlorin surround and bind the magnesium atom. This is a stable ring-shaped molecule around which electrons are free to migrate. It also has side chains and a hydrocarbon trail Contains only methyl groups ( CH3 ) as side chains has a long hydrophobic tail, which anchors the molecule to other hydrophobic proteins in the thylakoid membrane of the chloroplast. It absorbs light from red, blue and violet wavelengths and gets its colour by reflecting green.

6. Function Used in oxygenic photosynthesis This photosynthetic pigment is essential for photosynthesis in eukaryotes, cyanobacteria and prochlorophytes because of its role as primary electron donor in the electron transport chain . Chlorophyll a also transfers resonance energy in the antenna complex, ending in the reactioncenter where specific chlorophylls P680 and P700 are located Within the reaction centers of both photosystems there are a pair of chlorophyll a molecules that pass electrons on to the transport chain through redox reactions

7. Chlorophyll b A second kind of chlorophyll is chlorophyll "b", which occurs only in "green algae’’ and in the plants. Chlorophyll b absorbs most effectively at blue 470 but also at 430 and 640 Molecular formula - C 55 H 70 O 6 N 4 Mg It is an accessory photosynthetic pigment Molecular structure consists of a chlorin ring with Mg center The chlorin ring is a heterocyclic compound derived from pyrrole Four nitrogen atoms from the chlorin surround and bind the magnesium atom also has side chains and a hydrocarbon ( phytol ) tail Pyrrole ring II contains an aldehyde group (-CHO)

8. Function Absorb energy that chlorophyll a does not absorb Functions as a Light-harvesting Antenna in Photosystem I

9. XANTHOPHYLL Xanthophyll are yellow pigments that form one of two major groups of the carotenoids group It is generally a C 40 terpenoid compounds formed by condensation isoprene units xanthophylls contain oxygen atoms Xanthophylls contain their oxygen either as hydroxyl groups and/or as pairs of hydrogen atoms that are substituted by oxygen atoms acting as a bridge (epoxide )

10. FUNCTION Xanthophyll acts as an accessory light harvesting pigment Have critical structural and functional role in the photo synthesis of plants and algae Also serve to absorb and dissipate excess light energy, Or work as antioxidants Xanthophyll may be involved in inhibiting lipid peroxidation

11. FUCOXANTHIN Fucoxanthin is a carotenoid, which performs a limited form of photosynthesis in Brown Algae ( Phaeophytes ). and other heterokonts . It is responsible for the brown or olive-green colour of these algae . Molecular formula C 42 H 58 O 6 Fucoxanthin absorbs red light to perform photosynthesis The pigment is produced in abundant quantities by the following edible brown algae : Laminalia japonica, Undaria pinnatifida , Sargassum fulvellum etc It is a xanthophyll — an oxygenated carotene, or plant pigment

12. FUNCTION It is a xanthophyll — an oxygenated carotene, or plant pigment Brown algae is an abundant class of plants, with most species living in the ocean and employing fucoxanthin for photosynthesis The substance is sensitive to shorter wavelengths of light, so most brown algae live in shallow water It is the main carotenoid produced in brown algae as a component of the laight harvesting complex for photosynthesis and photoprotections fucoxanthin as an anti-obesity substance

13. PHYCOCYANIN Phycocyanin is a pigment-protein complex from the light-harvesting phycobiliprotein family , along with allophycocyanin and phycoerythrin It is an accessory pigment to chlorophyll Water-soluble, so they cannot exist within the membrane like carotenoids Phycocyanin is a characteristic light blue color , absorbing orange and red light, particularly near 620 nm (depending on which specific type it is), and emits fluorescence at about 650 nm (also depending on which type it is ). Phycocyanins are found in Cyanobacteria (previously called blue-green algae). The most important pigment in Spirulina

14. FUNCTION Phycocyanin (Pc) is a phycobiliprotein that has been recently reported to exhibit a variety of pharmacological properties. In this regard, antioxidant, anti-inflammatory, neuroprotective and hepatoprotective effects have been experimentally attributed to Pc it reduces carbon tetrachloride ( CCl (4))-induced lipid peroxidation in vivo . Phycocyanin is related to the human pigment bilirubin, which is important to healthy liver function and digestion of amino acids. It imparts its anticancer property to Spirulina . Help in curing anemia

15. PHYCOERYTHRIN Phycoerythrin (PE ) is a red protein-pigment complex from the light-harvesting phycobiliprotein family , present in red algae and cryptophytes , accessory to the main chlorophyll pigments responsible for photosynthesis . it is composed of a protein part covalently binding chromophores called phycobilins . In the phycoerythrin family, the most known phycobilins are: phycoerythrobilin , the typical phycoerythrin acceptor chromophore , and sometimes phycourobilin Phycoerythrins are composed of (αβ) monomers, usually organised in a disk-shaped trimer (αβ) 3 or hexamer ( αβ) 6 In red algae they are anchored to the stromal side of thylakoid membranes of chloroplasts, whereas in cryptophytes phycobilisomes are reduced and are densely packed inside the lumen of thylakoids.

16. Phycoerythrin is an accessory pigment to the main chlorophyll pigments responsible for photosynthesis . The light energy is captured by phycoerythrin and is then passed on to the reaction centre chlorophyll pair, most of the time via the phycobiliproteins phycocyanin and via allophycocyanin R- Phycoerythrin and B- Phycoerythrin are among the brightest fluorescent dyes ever identified FUNCTION

17. CONCLUSION From the above discussion it can be cncluded that Algae are a major group of photosynthhetic organism In algae pigments are the means by which the energy the energy of the sunlight is captured for photosynthesis There are various group of algae and can be classified from one another by the presence of the photosynthetic pigments The photosynthetic pigments are- chlorophyll a , chlorophyll b, xanthophyll, fucoxanthin , phycoerythrin , The pigments have wide range of function starting from photosynthesis to photoprotective activity

18. REFERENCES Mitra,D.,Guha,J.,Chowdhuri,S.K.2009.Studies in Botany.Vol (I).2nd ed.Moulik Library,Calcutta Kumar,P . and Mina,U.2013.Life Sciences Fundamentals and Practice.Vol (II).3 rd ed.Pathfinder Publication,New Delhi http :// educationportal.com/academy/lesson/chlorophyll-in-plants-benefits-function-definition.html#lesson www.majordifferences.com/2013/05/difference-between-chlorophyll-and.html www.oilgae.com/algae/cla/chl/chl.html http:// www.oilgae.com/non_fuel_products/betacarotene.html

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