Lectures 15 Membrane Structure and Transport-BW

S ingle lipid more ridgid important effects mim phase

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Unformatted text preview: m phase trasnsition Fused ring structure is rigid; can disrupt regular interactions between phospholipid tails membrane fluidity Phase Transition (Tm) Looks at the effecct of temp on fl uidity - membrane at low temp will more solid - increase temperature - rapid rise - from solid to fl uid state - ther ise is called metling temp - temp. organism alter composition of membrane to deal with the temperature more unsatured fatty acid in membane - so the temp will c onteract - if the temp is cold then the membrane will become more solid - therefore the resitict movement of molecules in and out - not going to be good for delveipment of the plant incorperating more unsaturted fatty acid - counteract the effects of the decrase in the temperature - dont make it too fl uid - Unsatured - too cold More saturated where to hot Temperature affects the fluidity of the membrane. Melting temperature (Tm) depends on fatty acid chain length and extent of unsaturation. Examples 3/11/13 MCB 2000 Lectures 15 The Fluid Mosaic Model Describes Membrane Dynamics S. J. Singer and G. L. Nicolson The phospholipid bilayer is a fluid matrix Lipids can undergo rotational and lateral movement Prospoed by two scienisits - describe the lipid biplay - fl uid matrix - dynamic structure - membrane = fl uid matrix - movement of phosplipds and protein within the membrane inner leafl et phosphlipd fl ip to outerleafet - during programmed cell death - aptosis (cell death) - most of the movemetn lateral - 3/11/13 MCB 2000 Lectures 15 Fluorescence Recovery After Photobleaching (FRAP) measures lateral movement of lipids and proteins. How do you lateral diffusion? - FRAP - have your cell and your goign to esstenially expose it to high intensity fl ourscence wavelength - directing fl ourscence beam to certain parts of the c ell - hole iwll appear - allow time to recover - molecules move to the belneded out membarne to restore its normal sate - belench out and then begins to be restored - key evidence - membrane c omplent move they dont stay put 3/11/13 MCB 2000 Lectures 15 Proteins span the membrane (integral) or are loosely associated (peripheral). Classes of proteins: 1. Integral Proteins (a, b ) 2. Peripheral Proteins (c, d ) 3. Lipid anchored proteins (e) Peripheral protein - do not interact with the hydrophobic core of membrane E) tail will instere itself intot the lipid bilayer - rest of the molecuel is external 3/11/13 MCB 2000 Lectures 15 Peripheral Proteins Peripheral proteins are not strongly bound to the membrane They can be dissociated with mild detergent treatment or with high salt concentrations How do you know you have a peripheral protein? - how wil it interact? electorsatic or hydorgen bonding - in order to remove a peripheral protein - use salt to get it off the membrane 3/11/13 MCB 2000 Lectures 15 Integral Membrane Proteins Are Firmly Anchored in the Membrane Integral proteins are strongly imbedded in the bilayer They can only be removed from the membrane by denatur...
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