OBJECTIVE LIFE SCIENCE
CELL BIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The orientation of the hydrophilic phospholipid heads towards the proteins
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The formation of a hydrophobic region on the surface of the membrane
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The placement of integral and peripheral proteins in the membrane
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The interactions due to amphipathic properties of phospholipids
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Detailed explanation-1: -The Davson–Danielli model of membrane structure proposed that membranes were composed of a phospholipid bilayer that lies between two layers of globular proteins, as shown in this diagram. What evidence supported this model? The hydrophobic regions of protein would be in contact with water.
Detailed explanation-2: -In 1935, the Sandwich or Lamellar Model or bimolecular leaflet model was suggested by Danielli and Davson. According to which plasma membrane contains a phospholipid layer and in between two layers of protein like a sandwich in P-L-L-P structure with nonpolar tails of the lipid bilayer in the center.
Detailed explanation-3: -High magnification electron micrographs of membranes were made in the 1950s, which showed a railroad track appearance-two dark lines with a lighter band between. Proteins appear dark in electron micrographs and phospholipids appear light, so this appearance fitted the Davson-Danielli model.
Detailed explanation-4: -The Davson-Danielli model depicts a layer of globular proteins over the phospholipid bilayer. It was falsified by fusing two cells together, dyed different colors. The colors mixed, which proved that the structure was fluid rather than rigid, that of which was proposed by the Davson-Danielli model.