Lectures 15 Membrane Structure and Transport-BW

2000 lectures 15 lipid bilayer is a favored structure

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Unformatted text preview: is a Favored Structure Membranes form due to the amphipathic property of phospholipids: Box shows the plasma membrane is a bilayer ***Hydrophobic Effect Polar head group interacts with water. Hydrophobic tails interact with each other; avoid water. 3/11/13 MCB 2000 Lectures 15 Eukaryokarote membrane - not plants they dont have c holesterol - the mam. c onstatn colesterol - most importantly the plasma membrane - has ring s tructure - very planar and hydrophobic - you have one hydroxyl group gives cholesterol the imporant property c onsidered amphipathic Membrane Components The precuroser for making steriod hormones - derivie from steriod nueculus Also amphipathic High content in plasma membrane; found in animal, not plant membranes 3/11/13 MCB 2000 Lectures 15 Membrane Fluidity Depends on properties of fatty acid chains in phospholipids Length of chain Double bonds O rganisms and plants can modifi ty - to withstand heat and cold - membrane fl uidity - when you talk about a membrane gonig to have some types of s olid and fl uid characteristics - the more fl uid it is the greater the permeability - because not packed as tightly - what to restict permebailty - pack in molecules closer together ( or more fatty acids taht are saturated in your phosphlipds) - two factos that c ontrol fl uid (one fatty acid and one cholroesteol) focusing on the plasma membrane - plasma highest in choldestrol - property of the fatty acid - if y ou have a saturated fatty acid - can pack mulit phosphlipdi tightly - saturated and unsatured fatty acid - will open up some space - waht determines the fl uidity? - going to put in unsaturated other factor is the life of the cahin - long chain fatty acid ( 18 carbons) verus 4 or 6 which is more fl uid? shorter or longer chain? - short chain because n /11/13 3oncoavalent interaction contribue to stability s horter the chain the fewer of the interactions MCB 2000 Lectures 15 Membrane Fluidity Cholesterol content (animal cells) -OH groups forms H-bond with carbonyl of phospholipid head group Can from complex with specific phospholipids (sphingolipids); may increase rigidity and order in Choldestoral can interact with polar head of the phosplipd bilayer - cholesterol going within the regions of membrane, i.e. tail - one level cholesterol increase membrane fl uidity because it distrubtes the interaction between the hydrophoic tail and seprates them out - however there are regions of the lipid rafts membarne that are more enriched with phosphlipid - can be present in the membarne and they are typically located in pathches - not uniformity distributed - choldrestol interacting with spingolipds - arrangedment - lipid wrap - region of the membrane - unique - signal trasnductino r oles - endocytosis - membrane dynamics - within the region goingt have a decrease in 3/11/13 MCB 2000 Lectures 15 membrane fl uid - cholesterol has two opposing effects - increase infl uid if evenly distrubted s ingle lipid more ridgid - important effects mi...
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