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.
Checkpoints and Cell Cycle Control Cell cycle checkpoints are control mechanisms which ensure the fidelity of cell division within eukaryotic cells. These checkpoints confirm w
Results of Mitral Valve Replacement: The risk of mitral valve replacement is reported as 3-5 per cent. It also depends on multiple factors like age, functional clas
how the blood is circulated with the help of heart
Define Tests for the Presence of Exoenzymatic Activity? Microorganisms require various micro- and macro-nutrients for energy production and growth. These are obtained from the
which area of the basal nuclei is responsible for controlling appendicular muscle tone?
Estimation of Depth of Burn Injury: A thermal injury is described as partial thickness or full thickness, depending on the depth and severity of tissue damage a) First D
Polysaccharides and Oligosaccharides are both parts of carbohydrate molecules, but they vary in complexity and size. The Oligosaccharides are much easier and smaller, according to
Is crossing over important for the diversity of biological evolution? Sexual reproduction and recombination of linked genes (crossing over) are, with mutations, the main instru
why sporophyte of psilopsida is rootless
How are mineral salts, water and food (sugar) transported throughout the plant? Mineral salts, Water and sugar are transported throughout the plant through conductive vessels f
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