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
What are the target organs upon which insulin and glucagon act? Glucagon mostly acts upon the liver. Insulin acts in general upon all cells. Both also act upon the adipose tiss

What is Active Transport--Secretion This method is now a well accepted process of aqueous formation. The rate of aqueous humour formation depends on the rate of active solute

Q. Show the Use of Incineration for sterilization? This is an excellent method for rapidly destroying materials such as soiled dressings, animal carcasses, bedding and patholog

Effects of Noise - Noise Pollution Noise can affect in the following three ways: Interferes with communication, Diminishes hearing and Affects health and even

What are some evolutionary advantages of animals with complete digestive tube? The complete digestive tube permits animals to continuously feed themselves without waiting for r

explain digestion in protozoans

ALEURONE GRAINS - Also known as Plant lysosome , because they contain hydrolytic enzymes. Consists of Proteins. They are also known as Aleuroplast because they are ric

Q. What do you mean by Taxonomist? Modern classification systems are based on many types of evidence. A truly natural classification is obtained from analysis and harmonisation

Q. What are the three major renal processes that combined produce urine? Urine is made by the occurrence of three processes in the nephron that are tubular resorption, glomerul

What are three main problems with having only two kingdoms There are three main problems with having only two kingdoms. The first problem concerns the unicellular flagellates