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.
It is a category of viruses having RNA genome and reverse transcriptase enzyme within virus cuspid.
Explain the Chemical Properties of Monosaccharides? As you already know the chemical properties of monosaccharides depend on the presence of the hydroxyl the aldehyde or the ke
How can the visual deficiencies known as myopia and hypermetropia be optically explained? Myopia is the visual condition in which the images are produced before (in front of)
Q. One characteristic of the DNA molecule is its replication capability. What are the consequences of failures during the DNA replication? Ideally the DNA molecule should replicate
In F2 generation of a hybridization for a given trait conditioned by a pair of alleles T and t, according to Mendel's first law what are the genotypes of each phenotypical form? An
Diversity is defined as the no of species present in a community termed as "species richness". We can represent species biodiversity at different geographical scales as alpha, beta
Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4
What are trophic levels? How many trophic levels can a food chain have? The Trophic levels correspond to positions on a food chain. thus producers always belong to the first tr
Roller Pump: This is the type most commonly used in clinical perfusion. It has a circular metal housing inside which there is a rotating urn with two rollers fixed at 180 degrees
Cilia and flagella are structures found in various prokaryotes as well in some eukaryotic cells. They play defense, nutrition and movement roles for the cell. In eukaryotic cells 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