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

Cell surface junctions, CELL SURFACE JUNCTIONS (1 )      Desmosomes (...

CELL SURFACE JUNCTIONS (1 )      Desmosomes (Maculae adherence) - Thickened circular areas on P.M. of adjacent cells with radiating fibrils in cytoplasm. These fibrils calle

Drug dependence, DRUG DEPENDENCE - Some drugs are prescribed by doctor ...

DRUG DEPENDENCE - Some drugs are prescribed by doctor for the prevention or treatment of a disease. Some drugs are used for long periods. A person becomes addict to these

Arthropods - regeneration in invertebrates, Arthropods - Regeneration in In...

Arthropods - Regeneration in Invertebrates Among arthropods like insects, crustaceans, centipedes, scorpions and spiders, the capability of regeneration is low or not present.

What is the impaired healing, Impaired Healing and Infection Because of Imp...

Impaired Healing and Infection Because of Improper Flap Design The oral field in itself is a contaminated area due to the presence of the normal oral microflora. Improper flap

How old is the earth, How old is the earth? It is believed that the ear...

How old is the earth? It is believed that the earth is about 4.5 billion years old.

Define translation phase of gene expression process, Define Translation Pha...

Define Translation Phase of gene expression process? The NDA which the transcript into m RNA is translated into protein with the help of ribosomes, m RNA, amino acids, a number

Which is the autotrophic group responsible for production, Which is the aut...

Which is the autotrophic group responsible for the production of most part of the molecular oxygen of earth? Cyanobacteria and Algae of the phytoplankton are the organisms that

Monounsatuated fats required for dyslipidemia, Q. Monounsatuated fats requi...

Q. Monounsatuated fats required for dyslipidemia? Monounsatuated fats (MUFA): These are liquid at room temperature, the highest food source being olive oil, canola oil, rapesee

Why bacteria can be transmitted from person to person, Identify three ways ...

Identify three ways that bacteria can be transmitted from person to person. Diseases affecting nerves contain botulism and tetanus; diseases affecting the intestine include sa

Structure of myofibril, STRUCTUR E OF A MYOFIBRIL - The dark bands ...

STRUCTUR E OF A MYOFIBRIL - The dark bands of the myofibril are termed the A-bands (Anisotropic bands). Each A-band has at its middle a light zone called H-zone (Henson'

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