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

Cytosol of prokaryotes, The  citric  acid  cycle  functions  in  the  mitoc...

The  citric  acid  cycle  functions  in  the  mitochondria   of  eukaryotes  and  in  the cytosol of prokaryotes. The Succinate dehydrogenase, the only membrane-bound enzyme   in t

Explain hiv/aids, Explain HIV/AIDS HIV/AIDS is another example of  chro...

Explain HIV/AIDS HIV/AIDS is another example of  chronic infections.  Its existence was discovered recently in 1981. The spread  of  HIV infection  is widespread  and  can  pro

Effects on ecosystem - air pollutants, Effects on Ecosystem - Air pollutant...

Effects on Ecosystem - Air pollutants The effects of pollutants on ecosystem become visible after a long period of exposure. In highly industrialised countries the vegetation

Mitosis, explain mitosis in detail

explain mitosis in detail

Mesophytes, Mesophytes These plants grow in moist habitats and well-aer...

Mesophytes These plants grow in moist habitats and well-aerated soils. They prefer soil and air of moderate humidity but fail to swive in areas with water-logged soils or oveta

Venous system, VENOU S SYSTEM It is collecting system formed by the...

VENOU S SYSTEM It is collecting system formed by the uniting branches as smaller and then larger veins and venacava leading to the heart. Blood from anterior part of the

Explain the metabolism - zinc, Explain the Metabolism - Zinc? Zinc has ...

Explain the Metabolism - Zinc? Zinc has been found to play an important biological role in our body. Zinc ions can be chelated and precipitated by a number of chelating agents

What carbohydrates does a plant make from glucose, (a) What carbohydrates d...

(a) What carbohydrates does a plant make from glucose? (b) Which of these carbohydrates is transported round the plant? (c) Which carbohydrate is the main s

Explain the transmission electron microscope, Explain the Transmission Elec...

Explain the Transmission Electron Microscope Here, thin and dehydrated specimen is used. Electrons pass through the specimen and form image on to photographic film. These are u

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