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.
Species diversity An important attribute of a community is its species diversity. The diversity is calculated both by the number of species (richness) and the relative abundanc
Novel Sources of Natural Colourants Microbial sources Production of materials by microbial cultures has several advantages. The rapid growth of microbes cuts the productio
Even though association between GAS pharyngitis and the ARF is fairly well established, the exact pathogenic mechanisms are not clearly understood. However, two mechanisms are post
What evidence did Charles Elton collect that suggested that fluctuations in hare and lynx populations were related? What other evidence shows that these fluctuations ma
DIGESTION OF FOOD MATERIALS Digestion, you know, involves the mixing of food, its movement through the digestive tract and chemical breakdown of the large ntolecules of food
What is the evolutionary advantage of the occurrence of sperm cells and larval stage in the life cycle of sponges? The sexual reproduction in sponges, in addition to contributi
Explain about the Demand curve or schedule in short. The demand curve or demand schedule shows the total quantity purchased through all buyers, within aggregate, into the marke
Define Techniques for Measuring Body Composition - Underwater weighing? Underwater weighing (densitometry): It applies the Archimedean principle of water displacement by the fu
what is human circulatry system
Why are the recombinant DNA technology and the nucleus transplantation technology still dangerous? A recombinant DNA technology and the nucleus transplantation technology (clon
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