Cell Membrane
<p>Feb 25, 2015 08:19 PM also see part 2 etc. Exclt instructor !</p>
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lipid bilayer: 6 to 10 nm thick; (his claim)</p>
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he shows how lipid molecules cluster (in order to increase entropy)
by excluding more water moledules
(more water is ordered if the phospholipid molecules are apart.</p>
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Fluid Mosaic model:</p>
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sterols like cholesterol.</p>
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RBC has ion channels...</p>
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actin maintains cell shape</p>
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and spectrins....</p>
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golgi apparatus abt 55% lipid
plasma membrane is 50/50
and other membranes are also abt 50/50</p>
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excpt for inner mitochondrial membrane is predom protein (cytochromes etc)</p>
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part 2 *</p>
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use SEM scanning EM to examine....</p>
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membrane is abt 6 to 10 nm (a DNA is 2 nm)</p>
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ribosome is about 25 nm.</p>
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headgroup is hydrophilic...</p>
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3 types of membrane lipids</p>
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phospholipids
glycolipids (cerebrosides and gangliosides)
and sterols. (chole and ergosterol)</p>
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phospholipids
can by glycerophosphates and
sphingolipids sphingosine backbone... sphinomyelin...</p>
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many more phospholipids in humans</p>
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phosphotidyl choline etc.</p>
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myelin is 80% lipid and 20% protein</p>
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phospholipids are phos.. glycerides and sphingomyelins</p>
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part 4 </p>
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the longer the fatty tail is in saturatged FAs (no dbl bonds), the higher the melting point</p>
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the more dbl bonds, the lower the melting point.</p>
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intergral protein goes across; peripheral proteins always face cytoplasm...</p>
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glycolipids always face out.</p>
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look at RBC:</p>
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phos choline outer membr leaflet
distrib of difft types of PLs varies.</p>
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kinks create gaps... sterols fill the gaps...</p>
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cholest incr membrane flexibiility... fills gaps. choles. is also amphipathic</p>
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high concen of choles incr fluidity of membrane.</p>
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Part V... membrane dynamics..</p>
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lateral diffusion goes fast...</p>
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transbilayer diffusion is v slow...</p>
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catalyzed: flippase, floppase, scramblase.;</p>
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