STRUCTURE OF CHLOROPHYLL

Detailed note on chlorophyll.

1. STRUCTURE OF CHLOROPHYLL ,CHLOROPLAST & PHOTOSYSTEM 1 AND 2 SUBMITTED BY SHEFI VARGHESE 1 ST M.Sc FTQA MRC,MUNNAR

2. chlorophyll Chlorophyll is a green compound found in leaves and green stems of plants. chlorophyll was a mixture of two compounds, chlorophyll-a and chlorophyll-b. Chlorophyll is remarkably similar in structure to hemoglobin. Chlorophyll is found in virtually all photosynthetic organisms, including green plants, cyanobacteria, and algae. It absorbs energy from light; this energy is then used to convert carbon dioxide to carbohydrates.

3. Structure of Chlorophyll Chemically,chlorophylls are complex magnesium-pyrrole derivatives. The chlorophyll molecule consist of a central metal core ie, magnesium surrounded by a nitrogen- containing structure resulting in a porphyrin ring . A number of side chains atached to the ring structure,of which an important one is , the side chain of a long hydrocarbon called phytol ring 3. Chemical formula:- C55H72MgN4O5

4. chloroplast

5. Structure of Chloroplast Main site of photosynthesis in plants. Chiefly occur in the mesophyll of cells. Food producers of plants. Chloroplast is found in all higher plants. They are double membrane organelle with the presence of outer,inner and intermembrane space. 2 distinct regions are present:- Grana and Stroma

6. The chloroplast structure consist of following parts:- Membrane envelope intermembrane space Thylakoid system stroma Grana Chlorophyll

7. Photosystems The light absorbing photosynthetic pigments are arranged on the thylakoid membranes of chloroplast in two interacting complexes,called pigment systems or photosystems. There are 2 types :- Photosystem 1(mainly present in unstacked membrane)and Photosystem 2(mainly in stacked membranes). Each photosystem consist of many thousand photosynthetic units called quantasomes

8. QUANTASOMES Quantasomes are closely packed arrays of spherical or oblate granular particles ,regularly arranged on or in chloroplast thylacoids. Light harvesting fu n ctional units of chloroplast,capable of carrying out photochemical reactions. In green plants,each quatasomes consist of 200-400 chlorophyll molecules and many accessory pigments molecules,all associated with specific proteins.

9. Differences between PS-I & PS-II Photosystem- I I nvolved in both cyclic and non-cyclic photophosphorylations. Receives eectrons from PS-1 and PS-2 and forms a strong reductant which reduces NADP to NADPH + H. Not involved in the photolysis of water and the release of oxygen. the reaction centre is P700. The absorption peak of the reaction centre is at 700nm. Photosystem -II I nvolved only in non cyclic photophosphorylation Donates electrons to PS-1 for reducing NADP to NADPH + H Involved in the photolysis of water and the release of oxygen. The reaction centre is P680 The absorption peak of the reaction centre is at P680nm.

10. reference Britannica, T. Editors of Encyclopaedia (2022, August 31). chlorophyll. Encyclopedia Britannica. https://www.britannica.com/science/chlorophyll