Plasma membrane By KK Sahu Sir

Introduction
Definition
Chemical composition
Molecular Structure of PM
Bilayel Model
Garter and Grendel s Model
Overton e Model
Fluid Mosaic Model
. Membrane Protein
Transmembrane Protein
Exterinsic Protein
non cytosolic Protein
6. Protein complex in pm.( cell coat)
7. Function of PM
8. Referance

1. PLASMA MEMBRANE By KAUSHAL KUMAR SAHU Assistant Professor (Ad Hoc) Department of Biotechnology Govt. Digvijay Autonomous P. G. College Raj-Nandgaon ( C. G. )

2. Synopsis Introduction Definition Chemical composition Molecular Structure of PM Bilayel Model Garter and Grendel s Model Overton e Model Fluid Mosaic Model 5. Membrane Protein Transmembrane Protein Exterinsic Protein non cytosolic Protein 6 . Protein complex in pm.( cell coat) 7. Function of PM 8. Referance

3. Introduction The cell membrane is selectively permeabl  to ions and organic molecules and control the movment The  cell membrane  (also known as  that separates the interior of all cells from the outside environment the plasma membrane or  cytoplasmic membrane) is a biological membrane. This membrane was called cell membrane by C.Nageli and C.Cramer in 1855 and plasma membrane by J.Q.Plower in 1931. plasma membrane is a dynamic membrane that participate in selective permeability receive signal cells recognition adhesion and communication.

4. Deffination The cell membrane is primarily composed of a mix of proteins and lipids While lipids help to give membranes their flexibility, proteins monitor and maintain the cell's chemical climate and assist in the transfer of molecules across the membrane. Chemical composition Lipid protein carbohydrate

5. Lipid The cell membrane consists of three classes of  amphipathic  lipids: phospholipids,  glycolipids , and cholesterol. In  RBcs  studies, 30% of the plasma membrane is lipid. The lipid molecules make a bilayer 4.5 nm thick . A lipid molecule is amphipathic and consists of two parts a head (glycerol ) which is hydrophilic (water soluble or polar).

6. Proteins The major functions attributes to pm are actually performed by membrane protein . which constitute 20% to 70 % of the membrane by mass. like lipid molecule ( glycolipids ),protein also have oligosaccharide chains attached to them ( glycoproteins ). Extrinsic protein / peripheal protein Intrinsic protein structure protein Glycoprotein Lipoprotein Enzymatic protein Carrier protein

7. Carbohydrate Plasma membranes also contain carbohydrates predominantly  glycoproteins but with some glycolipids ( cerebrosides  and  gangliosides )

8. Molecular structure of plasma membrane Bilayer model =present in the two layer potein and lipid Danielli and Davson Model Danielli and devsion (1935) therefore proposed that pm contained a lipid bilayer with protein on both surface . Initially they supposed that protein existed as covalently bonded globular structure bond to the polar ends of lipid . Subsequently they developed appears to be smeared over the hydrophilic ends of the lipid bilayer .

9. B. Unit membrane model Robertson in 1959 in the form of his unit membrane concept. This concept of unit membrane with three layers(two protein layers and one lipid bilayer ) Thickness of unit membrane (10nm) was found to be greater in pm then in intracellular membrane of endoplsmic reticulum or golgi complex.

10. 2. Garter and Grendels model Gorter and Grendel in 1926 suggested that pm is composed of double layer of lipid molecules because they found that the lipid extracted from eryhrocyte membranes was twice the amount expected if a single layer was present throughout the surface area of these cell (hardly any membrane other than surface membranes are found in erythrocytes ).

11. 3. Overton Model Overton in 1902 postulated that plasma membrane is composed of a thin layer of lipid because it was observad that substance soluble in lipid could selectively pass through the membrane. Fig Overton model of plasma membrane

12. 4. Fluid mosaic model The  fluid mosaic model  explains various observations regarding the structure of functional  cell membranes  The model, which was devised by SJ Singer and GL Nicolson in 1972, describes the cell membrane as a two-dimensional liquid in. Cis integral protein Peripheral protein Trans integral protein Hydrophilic Hydrophobic Fig Fluid mosaic model of plasma membrane

13. Membrane Protein The major function attributed to pm are actually performed by membrane protein s which constitute 20% to 70 % of the membrane by mass. Transmembrane protien Covalently linked cytosolic extrinsic proteins Covalently linked non cytosolic extrinsic protein Non covalently linked extrinsic proteins

14. A. Transmembrane proteins (e.g. glucophorin ) or multiply helices or as barrels (e.g. porin )with a part of their mass on eiter slid of the membrane . when the polypeptide crosses the membrane only once it is describ as single pass transmembrane (e.g. glycophorin protein of human RBCs ) ,and when it crosses several times it is called a multipass transmembrane protein (e.g. band 3 protein of human RBCs ).

15. B. Covalently linked cytosolic extrisic protein Covalently linked cytosolic extrisic protein are located entirely in the cytosol and are attached to membrane by means of covalently attached fatty acid chains or prenyl groups .

16. C. Covalently linked non cyatosolic extrinsic protein Covalently linked non cytosolic extrinsic protein are found on the external surface of membrane and remain attached . each with the help of an oligosaccharide to the non cytoplasmic monolayer . Protein Complex and Membrane Glycocalyx or Cell Coat As discussed earlier most of the lipids in the outer monolayer of lipidbilayer and the non cytosolic external segments of the extrinsic as well as intrinsic protein protein of the pm are glycosylated they are therefore described as glycolipids and glycoproteins respectively. this is true of both animal and plant cell.

17. Fig Gyacocalyx on the surface of intestinal epithelium.

18. Functions of plasma membrane Transpot . Regulation of passage of material. Regulation of disstribution of ions. Response to environment. Contact with adjace cells. Reference Biochnology book by k.c.soni . cell and molecular biology book by p.k . gupta . w.w.w.google .com.