In 1962, Walter He described some micrographs as having the appearance of three
ID: 144001 • Letter: I
Question
In 1962, Walter He described some micrographs as having the appearance of three layers, with two dense outer layers and a lighter middle layer. is a bilayer. In his paper, Stoeckenius also stated hat previous papers Which of the following explains the appearance of a three-layer membrane in micrographs? had established the bilayer structure of the membrane. The hydrophilic heads of the bilayer show up as two dense layers, whereas the hydrophobic O tails show up as a single, lighter layer. The bilnyger consiats of a dense protein layer. a less dense ydrophobic layer, and a dense hydrophilic head group Some specialized cells in the mammalian gut have a triple layer of phospholipids. Proteins are denser than lipids and make up the two outer layers. The inner layer is made up O O O of less dense The plasma membrane is made up of three layers where i is impermeable and two layers where it is selectively permeable Stoeckenius, W Structure of the plasma membrane: An electron-microscope study. Circulation 1962 26, 1066-69 O Check Answer @ Next ExitExplanation / Answer
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Proteins are denser than lipid bilayer and make outer two layers. inner layer is made up of less dense phospholipids.
for reference here iam pasting some lines from origional paper.
The main difference in appearance between the bimolecular leaflet of lipid and the cell mnembrane is the lesser density and width of the outer layers in the case of the lipid leaflet. If an appropriate protein, e.g., globin, is added to the solution in which the lipid leaflets form, this protein is adsorbed onto the surface of the lipid layers and increases the density and the width of the outer dark bands seen in the electron micrographs to 25 A or more depending on the amount of protein present (figs. 4 and 5). Therefore, in such preparations, structures are found which are known to consist of one bimolecular layer of lipid with a layer of protein on both surfaces and which are identical in appearance to the image of the plasma membrane obtained by the same techniques
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spontaneously formed lipid monolayer in aquoes solution.
Protocells are self assembled spherical lipids that have property of wrapping inside materials like biological compounds. They are proposed to be first cells from which life started on this planet.
Experiments have already demostrated that how lipid molucles are capable of self assembly in aqueous substances. It is believed that amino acids or pseudo proteins might have got encapsulated inside these protocells and carried out biochemical activities inside these protocells.