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Topic 2 - lipid bilayer (lec 3)

2 saturation and length if u have unsaturatd fatty

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Unformatted text preview: e bond in them, they are not going to pack together as thightly as saturatd fatty acids, which are a simple long chain. When u have sturated fatty acids, they pack together thightly, and tend to give u a less fluid membrane. This is one of the reasons why most membrane phospholipids/phosphoglyceroid have one saturated and one unsaturated fatty acid, to give that right degree of fluidity. The length of the hydrocarbon chains in the fatty acids also helps to deterime fluidity. Long chains all pack together nicely. If u have a mix of long and short chains, they dont pack together nicely. They are therefore more fluid. You can increase membrane fluidity by going for a mix of long and short fatty acid chains. You can increase membrane fluidity by desaturating the fatty acid chains, by adding double bonds. 3) Polarity of Head Group: Phophotidlecholine b/c of the structure of choline, it tends to adpot a very cylinderical structure, that packs together very nicely, and gives u rigid membrane/less fluid membrane. Phosphotidleytholamine, this head group its structure is more like a cone, it does not pack together as tightly, it is associated with more fluid membranes. 4) Presence of Sterols: Sterols have a four-ring framework, and that framework is realitively stiff, incomparison to fatty acid chains. When u insert a four-ringed structure into a membrane, at cold temps the siffness of the structure prevents the fatty acids from packing thightly, it tends to make the membrane more fluid. At a higher temp, when the memrane is fluid the four-ringed structure adds some stability, therfore makes it a bit more rigid. Overall sterols buffer the effects of temp. > Homeoviscous adaptation, normally temp changes will affect Properties: membrane fluidity Homeoviscous adaptation Alterations in lipid composition to maintain membrane fluidity at different environmental temperatures Responses within an individual organism Evolutionary responses Fig. 13.12 Moyes & Schulte 2008 PC/PE fluidity PC/PE fluidity Fig. 15-8, Sherwood et al. 2005 BIO 1140 –...
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