FLUID MOSAIC MODEL - with regions of fatty acid chain...

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FLUID MOSAIC MODEL The fluid mosaic model was first proposed by Singer and Nicolson . Lipids and proteins can readily move laterally and can also undergo rotation (Fig.1). The degree of membrane fluidity is determined by temperature and lipid composition. Lipids with shorter fatty acid chains are less rigid and remain fluid at lower temperatures. This is because interactions between shorter chains is weaker than for longer chains. Lipids containing unsaturated fatty acids increase membrane fluidity The = bonds introduce kinks, preventing tight packing of the fatty acids ( Fig. 2) . Cholesterol ( Fig. 4 ) with its hydrocarbon ring structure plays a distinct role in determining membrane fluidity. Polar hydroxyl group positions close to the phosphate head group. Rigid rings interact
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Unformatted text preview: with regions of fatty acid chain adjacent to phospholipid head groups. This interaction decreases the mobility of the outer portions of the fatty acid chains, making this region of the membrane more rigid, even at higher temperatures. On the other hand. .. Insertion of cholesterol interferes with interactions between fatty acids, thereby maintaining fluidity at lower temperatures. Cholesterol is not present in bacteria or plant cells. Plant cell membranes do contain sterols which function in a manner similar to cholesterol. In the fluid mosaic model of the membrane ----there are membrane proteins inserted into the lipid bilayer. The lipids provide the basic structure, but proteins carry out the specific functions of the different types of membranes ( Fig. 1 ) ....
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This document was uploaded on 11/03/2011 for the course BIOLOGY MCB2010 at Broward College.

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