Topic 2 - lipid bilayer (lec 3)

These difference come from the way the membrane is

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Unformatted text preview: riod and different sphingolipids are inserted into each part of the bilayer. Once they are inseretd into one leaflet, they tend to stay there. The lipid component may circle around, or rotate in spot, but will not go from one leaflet to the other. It is rare for them to go from one leaflet to the other b/c it is going to be hard for the polar head group to pass through the non-polar center of that bilayer. Pink = Outer Purple = Inner - Glycolipids are in the outer Properties of the lipid bilayer: membrane asymmetry Lipids distributed unequally between the two leaflets Established during membrane biogenesis Flip-flops vs rotation and lateral diffusion extracellular env’t cytoplasm Fig. 4.10 Karp 2010 BIO 1140 – SLIDE 14 Fig. 7-10 Becker et al. 2009 Properties: membrane fluidity Fluid nature of membrane essential for function Fluidity reflects C chain length and saturation Head group polarity Buffering effect of sterols Temperature High temperature Fig. 4.23 Karp 2010 Low temperature BIO 1140 – SLIDE 15 Fig. 13.12 Moyes & Schulte 2008 > Fludity is another membrane property. The degree of the fluidity of the membrane is very important in determining its function. You cannot have a membrane that is too fluid, b/c it wont be organized, and it can't be too rigid, b/c the functions of the membrane depend on it being mobile. Sensory receptors cannot work, if they cannot move around in the membrane. There are number of factors that affect the membrane fluidity: 1) Temperature: As the temp falls, the phospholipid in the membrane tend to pack together tightly. The hydrocarbon tails all pack together leaving u with a structure that is stiff. At higher temps the hydrocarbon tails are much more dynamic, u than end up with a more fluid structure. like butter in the fridge which is stiff and butter outside gets very fluid. Temp is important b/c it affects how the membrane lipids are packed together. 2) saturation and Length: If u have unsaturatd fatty acids, fatty acid that have at least one doubl...
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