Fluid mosaic model, Biology

FLUID MOSAIC MODEL

  • Proposed by Nicholson and Singer (1972)
  • Proteins and lipids are arranged in a mosaic fashion.
  • Lipids and proteins are in a semi fluid structure. Fluidity of P.M. is due to phospholipids. Phospholipids of P.M. are rich in unsaturated fatty acid that's why these occur as liquid.
  • Main component of cell membrane are phospholipids because these form structural frame work of cell membrane.
  • In lipid part, plasma membrane also contains cholesterol. Cholesterol is mainly found in inner half of the membrane. Cholesterol molecules are more rigid than the phospholipids and therefore, presence of cholesterol confers stability on eucaryotic membranes.
  • Procaryotic cell membrane lacks cholesterol. However, in some bacteria pentacyclic sterole like molecules termed as hopanoids are present. Hopanoids stabilize the bacterial membrane.

714_fluid mosaic model.png

P.M. may be termed as "protein icebergs in a sea of phospholipids". or Gulab jamun (protiens) in a concentrated solution of sugar (phospholipids).

Two types of proteins are found in P.M.

(i) Integral or intrinsic proteins - Tightly held to phospholipid. These also cover minute pores. These are 70% of the total protein. These proteins may traverse the complete thickness of P.M. Intrinsic protein form channels which provide a rapid passage to water soluble materials across the P.M.

Some intrinsic protein molecules extend through the membrane as single helix on both the sides. These called transmembrane proteins.

(ii) Peripheral or extrinsic proteins - 20-30% of total proteins.

  1. Superficially arranged on either side of P.M. and can be separated easily. These proteins have enzymatic activity and commonly called permeases. Extrinsic proteins can freely move in P.M. and regulate it's permeability. Extrinsic protiens function as carriers for the transport of material.
  2. "Spectrins" are helical extrinsic protein which found an cytosolic face of membrane attached to intrinsic proteins.
  3. Spectrins are part of cytoskeleton.
  4. Carbohydrates (oligosaccharides) in plasma membrane occurs only on its outer surface in form of Glycoproteins, glycolipids, lectins (antibodies, antigens) , sialic acid etc. So the two face of plasma membrane are asymmetrical.
  5. Glycoproteins and glycolipids help in cell recognition. Cells of same organism or of same tissue recognize each other with the help of glycoprotiens and glycolipids. Best example of cell recognition is fertilization where sperm and egg recognize each other.
  6. Beside all these compounds, P.M. have approximately 30 types of enzymes ( ATPases)
Posted Date: 10/5/2012 6:30:09 AM | Location : United States







Related Discussions:- Fluid mosaic model, Assignment Help, Ask Question on Fluid mosaic model, Get Answer, Expert's Help, Fluid mosaic model Discussions

Write discussion on Fluid mosaic model
Your posts are moderated
Related Questions
BLOOD COAGULATION -   DEFINITIO N - The property of blood to change from fluid to gel state within a few minutes of its coming in contact with air is called blood coag

What is the optimum temperature for catalyses? For any chemical reaction, the reaction rate enhances with temperature, so the higher the temperature, the faster the rate. For a

Q. What is the parasite that causes giardiasis? How is it transmitted and what are the typical manifestations of the disease? The Giardiasis is a protozoal infection caused by

Human respiration Human beings are adopted for terrestrial mode of life. They conduct pulmonary respiration. This system consists of external nostrils, nasal cavities, pharyn

COMPOSITION OF CELL WALL Cell wall composed of cellulose, hemicellulose, pectin, lignin, cutin & chitin. Cell wall consists of 3 parts - 1. Matrix Highly cross-

what is heterotroophic mode of nutrition?give some information about heterotrophic mode of nutrition?

ABA - Dormancy Abscisic acid functions as an antagonist of all three promoters like IAA, GAS and Cytokinins. ABA nullifies the activity of GA, IAA and cytokinin right by a)

Explain about lyophilic If the affinity between the dispersed phase and the medium is high, the dispersed phase is said to be lyophilic (solvent loving) or hydrophilic, in the

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Define Maternal Dietary Intake and Foetal Outcome? Among the various nutrients, energy intake appears to be the most crucial, for developing countries. Studies from India have