Plasma membrane( fluid mosaic model)ppt.

Short notes for fluid mosaic model

1. FLUID MOSAIC MODEL k.Kembadevi I- M.Sc biochemisry

2. Plasma Membrane The plama membrane,lipid bilayer . Plasma membrane is also called cell membrane. Plasma membrane is formed of glycoproteins & Phospholipids . These molecules are arranged in a definite pattern. Plasma membrane contains about 20%of water. Models of plasma membranes : 1.Translaminar model 2.micellar model 3.Biomolecular leaflet model 4.lattice Model 5.Fluid mosaic model

3. Fluid Mosaic Model Fluid Mosaic Model explains the structure of plasma membrane. The model was proposed by Singer & Nicolson in 1972. The plasma membrane consists of lipids& protein . The lipid is in the form of Fluid & the proteins are embedded here and there in the lipids in a mosaic pattern. Hence it is name “fluid mosaic model”.

4. Plasma Membrane Fluid Mosaic Model Thickness:75-100A ,pore size:7-10A

5. Chemical Composition Basic Structural frame work is the lipid bi-layer Made up of 3 Macromolecules. * Lipid * Protein * Carbohydrates Membrane Lipids, 75% phospholipids 20% cholesterol 5% Glycolipids

6. Proteins icebergs in the sea of lipids

7. Proteins Proteins are Alpha- Globular. They are 2 types: Extrinsic Proteins: It is also called as “Peripheral proteins”. Present on outer side of the Phospholipid bilayer . They are loosely attached to the Phospholipds molecules so are easily separated. They can move freely in membrane structure. Some proteins like permeable&translaces function as carriers for transport of material.

8. Intrinsic proteins : They are partially (or)completely embedded Phospholipids bilayer . They are strongly held to phospholipid molecules,so cannot be separated. They make 70% of total Plasma Membrane proteins. Some proteins are big&pass through the phospholipids bilayer and act as Trans-membrane proteins.

9. CarbohydratEs Presene of Carbohydrates along with proteins & lipids in the form of Glycoproteins & Glycolipids . Lipids: Lipid component consists of mainly Phosphoglycerides .

10. Glycolipids : Glycolipids from a protective coat(cell coat) around the cell. Glycoproteins and Glycolipids make plasma membrane asymmetric. Glycoproteins help in cell identification.Glycoproteins act as MHC (major histocompatibility complex) which act as finger print of cells. Plasma membrane is Quasifluid (semi-solid jelly ). Plsma membrane has 2 surfaces,cytoplasmic (or) cytosolic and exoplasmic .

11. Phospholipids: Phospholipids Bilayer arranged in such a manner that tails face each other & heads away from each other.Head -polar part it’s a Phosphate group. Weak van der walls force of attraction between phospholipid layer.Tail -non polar part,long chain fatty acids. Phospholipids are the main components of plasma membrane. Plasma membrane is lipoproteins & trilaminar phospholipid bilayer in fluidity.

12. Movement of Phospholipids : quasi fluid nature of lipid enable lateral movement of protein within in the overall bilayer . The ability to move within the membrane is measured as its fluidity. Types : transition movement : Movement of phospholipids in same layer. Flip flop Movement: Movement of phospholipids between two layers.

13. Cholesterol Cholesterol is also found in plasma membrane in between phospholipid molecules. Cholesterol is rigid so help in providing stability to Plasma membrane structure. Cholesterol is absent in membranes of prokaryotes. so stability is provided by pentacyclic sterols. Plasma membranes have about 30 type of enzyme. The arrangement of phospholipids form a water resistant barrier layer.

14. Functions of Membrane Ion Channels Carriers(transporters) Receptors Enzymes Cell identity markers( Glycoproteins & glycolipids ) Fluid nature important for : Cell growth Secretion Endocytosis Cell devision

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