Fluid mosaic model, Biology

Assignment Help:

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)

Related Discussions:- Fluid mosaic model

Rassenkreis and speciation, According to the current concept of speciation,...

According to the current concept of speciation, a widely distributed species should break up into partially isolated rule species. The different subspecies become differentiated fu

Illustrate numerical taxonomy, Q. Illustrate Numerical Taxonomy? Taxono...

Q. Illustrate Numerical Taxonomy? Taxonomy today is, in many dctails, different from what it was a generation ago. The use of computers by taxonomists has established an intere

Define requirements of vitamin a for infants, Define requirements of Vitami...

Define requirements of Vitamin A for infants? As for vitamin A deficiency, requirement of vitamin A is the most easy to meet as it is abundantly present in green and yellow veg

Reproduction in human beings, Are sperms being attacked by the body since t...

Are sperms being attacked by the body since they are foreign?

The exine layer, The Exine Layer It consists of two layers, inner (nex...

The Exine Layer It consists of two layers, inner (nexine) which is continuous and an outer (sexine) the sculptured one. The outer layer has ornamentations comprising rod-like

Individuals with tyrosinenmia, Individuals with tyrosinenmia have food patt...

Individuals with tyrosinenmia have food patterns very similar to the one for PKU discussed above. PKU is more common than tyrosinemia. Foods that are high in tyrosine and phenylala

Evolution of photosynthesis and aerobic respiration, Evolution of Photosynt...

Evolution of Photosynthesis and Aerobic Respiration It is assumed that the earlier form of the bacteria utilised H 2 S for the preparation of food. The following reaction shows

Elaborate evolution by natural selection , Elaborate Evolution by Natural S...

Elaborate Evolution by Natural Selection ? The conelaboratecept of natural selection lies at the heart of Darwin's Theory of Evolution. Darwin understood that plants and animal

Osmoregulation in terrestrial environment, Osmoregulation in Terrestrial En...

Osmoregulation in Terrestrial Environment  Earlier you have learnt about osmoregulation in aquatic environment. In this section, we shall study how the terrestrial animals cop

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd