PHOSPHOLIPIDS - SOURCE, STRUCTURE, TYPES AND FUNCTIONS

It is a presentation about phospholipids. It contains the structure, amphipathic nature, sources and detailed functions of phospholipids. Also it contains details on each subtypes of phospholipids with its structure.

1. SREE NANDANA S FOOD SCIENCE & TECHNOLOGY KUFOS PHOSPHOLIPIDS

2. INTRODUCTION Esters of fatty acids with alcohol containing a phosphoric acid and nitrogenous base . On hydrolysis - yield fatty acids, phosphoric acid, glycerol or sphingosine and a nitrogenous base . Amphipathic with a hydrophilic or polar head and a long hydrophobic tail . Major lipid constituents of cellular membrane - phospholipid bilayer .

3. STRUCTURE Backbone - Glycerol molecule serves as central core of the molecule. Glycerol backbone contains three carbon atoms . Sphingophospholipids contain sphingosine instead of glycerol. Fatty Acid Tails - Two fatty acid tails attached to the carbon in glycerol backbone. One fatty acid tail a ttached to sphingosine backbone. Fatty acid tails - hydrocarbon chains with 14-24 carbon atoms. Can be saturated or unsaturated.

4. Phosphate Group - A phosphate group attached to the C 3 of glycerol backbone / C 18 of sphingosine. A phosphorus atom bonded to four oxygen atoms. One oxygen atom bonded to glycerol/sphingosine backbone. Hydrophilic Head Group - Phosphate group linked to a hydrophilic head group Vary in composition and includes various functional groups (choline, ethanolamine, serine, inositol, or others). Determines the specific type of phospholipid. Gives rise to different subclasses of phospholipids.

5. AMPHIPATHIC NATURE Amphipathic molecule. Posses s both a hydrophobic and a hydrophilic component. Phosphate group - “head” - hydrophilic Chains of fatty acids - “tails” - hydrophobic. Phosphate group is negatively charged H ead - polar and hydrophilic . Phosphate heads - attracted to H 2 0 molecules. Lipid tails - uncharged, nonpolar, and hydrophobic .

6. OCCURRENCE Found in all plants and animals Part of the cellular and intracellular membranes . 1% of dry matter. Animal tissues rich in phospholipids - nervous tissue and egg yolk . Egg yolk - source of phospholipids for pharmaceutical purposes. Soybeans - rich source of phospholipids Soy and egg phospholipids used as emulsifiers .

7. CLASSIFICATION Phospholipids are classified into two:- Glycerophospholipid Sphingophospholipid

8. GLYCEROPHOSPHOLIPIDS Phospholipids derived from glycerol Hydroxyl groups at C 1 and C 2 of glycerol esterified to two fatty acids. C 3 of glycerol is esterified to phosphoric acid Form phosphatidic acid or diacylglycerol-3-phosphate .

9. Phosphatidic acid - simplest phosphoglyceride . Phosphoglycerides - derivatives of phosphatidic acid A key intermediate in the bio- synthesis of other phosphoglycerides . Phosphatidate - ionic form of phosphatidic acid In phosphoglycerides , phosphate group of phosphatidate becomes esterified to the hydroxyl group of alcohols or nitrogen bases.

10. Phosphatidylcholine Also called lecithin . Phosphoglycerols containing choline . Most abundant phospholipids of the cell membrane Make up a considerable proportion of the liver and brain. Occur in plasma as part of lipoproteins . Large proportion of body's store of choline .

11. Phosphatidylethanolamine Also called cephalin . Have nitrogenous base ethanolamine in place of choline. Thromboplastin for clotting - composed mainly of cephalins. A non-bilayer forming phospholipid +

12. Phosphatidylserine Contains the amino acid serine as nitrogenous base . Found in most tissues. Key role in cell cycle signaling , specifically apoptosis. Apoptosis – Programmed cell death in which a series of molecular steps in a cell lead to its death

13. Phosphatidylinositol I nositol - nitrogenous base. Precursor of second messenger . On stimulation by hormones - cleaved into diacylglycerol and inositol triphosphate - internal signals or second messengers. Important constituent of cell membrane phospholipid .

14. Plasmalogens Fatty acid chain at C 1 of glycerol is linked through an ether bond not ester bond. Three major classes – 1. Phosphatidalcholines , 2. Phosphatidalethanolamines 3. Phosphatidalserines . Found in myelin & cardiac muscle . Myelin - ethanolamine plasmalogens Heart muscle - choline plasmalogen.

15. Lysophospholipids Intermediates in metabolism of phosphoglycerides . Produced when one of the two acyl groups is removed from phosphoglycerides . Eg - lysophosphatidylcholine (lysolecithin) and lysophosphatidylethanolamine .

16. Diphosphatidyl glycerol Also called cardiolipin Two molecules of phosphatidic acid esterified through their phosphate groups to a glycerol Major lipid of mitochondrial membrane . Only antigenic human phosphoglyceride Recognized by antibodies raised against Treponema pallidum causing Syphilis. 1 2 3 4

17. SPHINGOPHOSPHOLIPIDS Derived from alcohol sphingosine No glycerol Sphingosine - an amino alcohol that contains a long, unsaturated hydrocarbon chain. Ceramide backbone - fatty acid attached to a long-chain amino alcohol . Fatty acids attached by amide linkage to NH 2

18. Sphingomyelin Only phospholipid in membranes not derived from glycerol. Amino group of sphingosine linked to a fatty acid by an amide bond Primary hydroxyl group of sphingosine is esterified to phosphorylcholine . One of the principal structural lipids of membranes of nerve tissues .

19. FUNCTIONS Structural Role in Membranes - Major building blocks of biological membranes. Selective Permeability  - Phospholipid bilayer acts as a selective barrier that regulates the entry and exit of substances into and out of cells. Membrane Protein Function  - Have a bility to control activity, location, and function of some membrane proteins.

20. Intrac ellular Signalling and Communication  - Platforms for activation of signalling proteins, hence s ignals transmitted across cell membranes easily. Energy Storage – If needed, f atty acid tails of phospholipids enzymatically cleaved through lipolysis.  Insulation of Nerve Impulse - Insulate the nerve impulse from the surrounding structures, eg . sphingomyelins act as an insulators in the myelin sheath around nerve fibres .

21. Cellular Trafficking - Involved in cellular trafficking activities like vesicle production, exocytosis, and endocytosis. Membrane Remodeling  - Participate in membrane remodeling processes like membrane fusion and fission - essential for cell division. Cellular Signatures and Recognition - Serve as biological signatures to differentiate cell types by supplying distinctive lipid profiles. 

22. Constituent of Lipoprotein - An important constituent of lipoproteins, the transport form of lipid. Emulsifying Agents - Good emulsifying agents, hence help in transport, intestinal absorption and metabolic interactions of lipids. Anti-cholesterol Agents – Helps in esterification of free cholesterol to form ester cholesterol and thus help in the removal of cholesterol from the body.

23. REFERENCE

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