Downloaded 27 times
More Related Content
Plasma membrane
- 1. PLASMA MEMBRANE STRUCTURE &FUNCTION PRESENTED BY, AKSHAYA ANIL S 3 M Sc BIOCHEMISTRY DEPT.OF BIOCHEMISTRY KERALA UNIVERSITY 1
- 2. PLASMA MEMBRANE Thin,fragile 5 – 10 ꞃm wide Lipid bilayer Polar head & nonpolar tail 2 Around 5000 plasma membrane stacked one above the other is equal to the thickness of a single page of the book…
- 3. HISTORY Ernest Overton(1890) Chemicalnature of outer boundary layer of the cell E.Gorter & F.Grendel(1920-1930) Proposed the biological membranes consists of bilayer Hugh Davson James & James Danielli(1935) Proposed lipid bilayer was lined on both sides inner & outer by a layer of globular cells S.Jonathan Singer & Garth Nicolson(1972) Prosposed fluid mosaic fluid 3
- 4. • Central dogmaof membrane biology • The structure and arrangement of membrane proteins occurs as a “mosaic” of discontinous particles that penetrate the lipid sheet • Protraits cell membranes as dynamic structures 4
- 5. • Membranes arelipid protein assemblies held together by non covalent bonds 5 LIPIDS •Phospholipids Glycerophospholipids Sphingolipids •Sterol Cholesterol CARBOHYDRATES •Glycolipids •Glycoproteins PROTEINS •Integral •Peripheral •Lipid anchored
- 6. 6 • Core membraneconsists of a sheet of lipids arranged in a bimolecular layer • Lipid bilayer,structural backbone provides barrier that prevents random movement of water-soluble materials into & out the cell • Protein part perform the specialized functions of the cell
- 7. • Contain awide diversity of lipids • Amphipathic PHOSPHOLIPIDS SPINGOLIPIDS CHOLESTEROL MEMBRANE LIPIDS 7
- 8. LIPID MOLE PERCENT PHOSPHATIDYLCHOLINE20 PHOSPHATIDYLETHANOLAMINE 11 PHOSPHATIDYLSERINE 4 PHOSPHATIDYLINOSITOL 2 CHOLESTEROL 49 SPINGOMYELIN 13 GLYCOLIPIDS 1 8
- 9. • Most membranelipids contains a phosphate group which them phospholipids • Phospholipids are built on glycerol backbone,so called phosphoglycerides • Membrane glycerides are diglycerides,only two hydroxyl group are esterified to fatty acid • 3rd group is esterified to a hydrophilic phosphate group 9
- 10. • Additional groupsattached with phosphoglycerides are small & hydrophilic • Together with the negatively charged phosphate group to which it is attached forms a highly water soluble domain called the head group 10
- 11. • Fatty acidchains are hydrophobic, unbranced hydrocarbons ~16-22 carbons in length Saturated Monounsaturated Polyunsaturated Membrane fattyacids 11
- 12. • Less abundantclass • Derivative of sphingosine • Sphingosine is a amino alcohol that contains a long hydrocarbon chain attached by its amino group 12
- 13. • Animal cellconstitute upto 50%lipid molecules in the membranes • Plant cells contains cholesterol like sterols • Cholesterol molecules are oriented with their small hydrophilic hydroxyl group towards the membrane surface & the remainder of the molecule embedded in the lipid bilayer • The hydrophobic rings of a cholesterol molecule are flat & rigid & it interfere with the movements of fattyacid tails of the phospholipids. 13
- 14. 14 LIPID HUMAN RBCHUMAN MYELIN E.COLI PHOSPHATIDIC ACID 1.5 0.5 0 PHOSPHATIDYLCHOLINE 19 10 0 PHOSPHATIDYLETHANOL AMINE 18 20 65 PHOSPHATIDYLGLYCEROL 0 0 18 PHOSPHATIDYLSERINE 8.5 8.5 0 GLYCOLIPIDS 10 26 0 SPINGOMYELIN 17.5 8.5 0 CHOLESTEROL 25 26 0
- 15. • Depending uponspecies carbohydrate content ranges between 2-10 % • More than 90% of the membrane’s carbohydrate is linked to proteins to form glycoproteins • Remaining is covalently linked to lipids to form glycolipid 15
- 16. • Present asshort , branched hydrophilic oligosaccharides • Oligosaccharides may attached to the amino acid by • Play a major role in mediating the interactions of cell • Involved in the sorting of membrane proteins to different cellular compartments • ABO blood grouping 16 N – glycosidic linkage O- glycosidic linkage
- 17. • Depending onthe cell type & the particular organelle within that cell,a membrane may contain 100s of proteins • Membrane proteins are grouped into 3 17 INTEGRAL PROTEINS PERIPHERAL PROTEINS LIPID ANCHORED PROTEIN MEMBRANE PROTEINS
- 18. • Penetrate thelipid bilayer • Transmembrane proteins • Have domains that protrude from both the extracellular & cytoplasmic sides of the membrane • Some have only one membrane spanning domain,some have multispanning • Constitute 25-30 % of all encoded proteins • Roughly 60% are drug targets 18
- 19. • Located entirelyoutside the lipid bilayer • Either the cytoplasmic or extracellular side • Associated with the surface of the membrane by non covalent bonds • Provide mechanical support for the membrane • Act as an anchor for the integral membrane proteins • On the internal plasma membrane surface function as enzymes,specialised coats,or factors that transmit transmembrane signals 19
- 20. • Located outsidethe lipid bilayer • Either on the extracellular or cytoplasmic surface • Are covalently linked to a lipid molecule that is situated within the lipid bilayer • Peripheral membrane proteins linked to phosphoinositol embedded in the outerleaflet of lipid bilayer by a small,complex olidosaccharide are called GPI anchored protein 20
- 21. COMPARTMENTALISATION SCAFFOLD BIOCHEMICAL ACTIVITIES PROVIDINGA SELECTIVELY PERMEABLE MEMBRANE TRANSPORTING SOLUTES RESPONDING TO EXTERNAL STIMULI INTERCELLULAR INTERACTIONS ENERGY TRANSDUCTION 21
- 22. REFERENCES • Cell Biology,GeraldKarp,7th edition • The Cell,a molecular approach,Geoffrey M.Copper & Robert e.Hausmann,7th edition • Lehninger Principles of Biochemistry,David L.Nelson & Michael M. Cox,7th edition 22