Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
CELL MEMBRANE
As discrete units of life all living cells are separated from each other and from their external environment by an extremely delicate (75 A to 100 a= 0.00075 to 0.001 thick ) covering membrane invisible under light microscope. The covering is called cell membrane, plasma membrane, cytoplasmic membrane or plasmalemma . Its presence was presumably visualized by Naegeli and Cramer(1855) and confirmed by E. Overton(1899) who believed that it was a double layer of lipid molecules .Since then, scientists have been making efforts to properly elucidate the molecular structure of this membrane. Gorter and gremdel (1925) postulated that it was a bimolecular lipid layer formed mainly of polar lipids with the double hydrophobic tails of their molecules in both layers directed towards the interior of the membrane, and their polar , hydrophilic heads, at the two surfaces of the membrane.
Danielli and Davson (1935) ascertained that the plasma membrane contains a good amount of globular proteins in addition to the lipids. They postulated a lipid protein bilaye r moderl of membrane structure with hydrated globular protein molecules adsorbed upon both exposed surfaces of the original biomolecular lipid layer, forming a protein lipid sandwich Later (1954) Danielli further proposed that there were places where lipid bilayer is perforated by pores lined by protein molecules, only polar solute molecules and ions can pass through these pores.
Using electron microscopy Robertson (1959) observed that the plasma membrane has a characteristic trilaminar appearance in a dark light dark or railway track pattern . Each dark line consists of a pleated sheet of protein on surface and sheet of polar heads of lipid molecules, while the light central line consists of a bilayer of nonpolar fatty acid of lipid molecules Robertson .called the trilaminar structure a unit membrane which is continuous with certain membranous structures present inside a cell.
What do you determine by Mantle? A thin sheetlike membranous extension of visceral mass of molluscs which forms two flaps of skin. Mantle secretes the shell on the dorsal side
Order of classification
who is the father of science
Define the Use of Computers in Numerical Taxonomy The use of computers in numerical taxonomy has made it possible to compare a large number of characters from many organisms wi
Explain the differences between a thrombus and an embolus. Include predisposing factors, mechanism of occurrence, treatment, and methods of detection with medical imaging, if any.
Mechanisms Of Endosseous Integration Three terms may be used to describe individual aspects of bone formation process that can occur around implants. They are Osteoconduction,
what are the classification of phylum platyhelminthes?
What is Binary Fission in cell reproduction? Cell division takes place in prokaryotic cells by binary fission, also called prokaryotic fission. In prokaryotes, DNA is contained
Osmoregulatory Animal An osmoregulatory animal is generally in an osmotic steady state even though there may be hourly and daily variations in osmotic balance. The concentrati
Q. Accessory Food Substances or Vitamins ? Bacteria also vary in their need for vitamins or accessory growth factors. Some microorganisms are unable to synthesize some or all o
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!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd