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.
Explain about the Osteomalacia - Deficiency of Vitamin D? It occurs when there is a lack of vitamin D and calcium, in women who have had many pregnancies, who subsist on a meag
Pheromones Serving Functions Other than Reproduction Besides sexual responses as described above pheromones mediate several other types of behaviour. Alarm pheromones have bee
Euthenics : It is the study of improvement of human races by providing better conditions. Euthenics means human improvement by altering external factors like as education or the co
Difference between Sympathetic and Parasympathetic Nervous System - S.NO . SYM P A THETIC PERASYM P A THETIC 1.
Q. How is the respiratory system in aquatic molluscs characterized? What adaptive respiratory structure do terrestrial molluscs present? In terrestrial molluscs the rich vascul
Explain Feeding Schedule in Infancy? 1) Milk feed 5-6 times/day. Continue breast-feeding. Exclusive breast-feeding up to 6 months even during illness. Follow demand feeding.
Which type of defense cell do bacteria attract and cause to multiply during the inflammation process? What is the name given to the waste material produced by the inflammation trig
Q. How does the sexual arousal mechanism in women facilitate fecundation? During sexual arousal in women the vagina secretes substances to neutralize its acidity thus allowing
Describe about the therapies of illicit drugs do to the brain Despite recent availability of new therapies for addiction, only a small proportion of people who need treatment
what is process of ultrafilteration involved?
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