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

2. Synopsis
1. Introduction
2. Definition
3. Chemical composition
4. 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
A. 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.

10. 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.

11. 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 ).

12. 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

13. 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

14. 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.
A. Transmembrane protien
B. Covalently linked cytosolic extrinsic proteins
C. Covalently linked non cytosolic extrinsic protein
D. Non covalently linked extrinsic proteins

15. 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 ).

16. 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 .

17. 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.

18. Fig Gyacocalyx on the surface of intestinal epithelium.

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