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
Q What is the usefulness of fungi for some industries? Fungi are industrially used in the production of fermented beverage, cheese, bread, and so on. A few fungi are very impor

Solubility of Oxygen It is also important to know that solubility of gases decreases with the presence of solutes or increased salinity. Table shows the solubility of oxygen a

using examples of invertebrate phyla illustrate how the increase in complexity is reflected by their nervous system?

what are enzymes?

Attempted Suicide: Suicide and homicide represent major source of morbidity and mortality in psychiatric practice.  Suicide means killing of  oneself.  An attempted suicide is

The branches of the left coronary artery are  anterio interventricular artery (AIV artery) and circumflex artery which is considered to be the continuation of the left coronary art

Explain the Explosion Puffing? Explosion puffing has been recognized as one of the most significant developments in dehydration technology. In explosion puffing, partially dehy

Q. Carbohydrates requirement in pectic ulcer? Carbohydrates: These should provide around 55 to 65% of the daily intake. Emphasis - J should be laid on the consumption of 60th s

Echinodermata - Regeneration in Invertebrates Asteroids (starfishes), ophiuroids (brittle stars) and crinoids (sea lilies) can reproduce their lost arms and although parts of

Q. Explain Aortic Valvuloplasty? Valvar aortic stenosis accounts for 4-6 per cent of CHD. LV Outflow Tract obstruction eventually leads to LV dysfunction and congestive heart f