ch.7 - membrane structure and function.docx

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Biological Sciences
BIOSC 0150
Christine Dahlin- Universityof Pittsburgh Johnstown

1 General Biology 1 Chapter 7Membrane structure and FunctionCell membrane Separate the inside from the outside of the cellSeparate cells and organellesSelectively permeableTransport across Ex nutrient entry waste exitCommunicationMajoradvantagesinternal solution can be different from external solution o Different environment for different activities Major components of cell membrane lipids proteins carbohydratesLipids phospholipidsserve as barrier between internal and externalProteinstransport and communicationCarbohydratesrecognition between cells and provide communication between cells Phospholipid Charged hydrophilic head phosphate Uncharged hydrophobic tails 2 fatty acidsAmphipathichydrophilic and hydrophobic regionA Membrane Made up of phospholipid bilayerHead facing water and cytoplasmTails cluster in because they try to get away from waterSelectively permeableonly some substances can cross easily Fluidityphospholipids are held together by hydrophobic interactionsweakLipids can move laterally but flip transversely are rare only once a monthThe packing of phospholipids with 2 hydrophobic region in the middle prevent hydrophilic head from crossing to membraneProteins are more less often to drift a little or more in directed mannerProteins that have cytoskeletal attachments dont move at all Membrane fluidity is important for function ButIf membrane is too fluidunstabletoo rigidno transport across enzymes dont workFluidity of membrane depends onsaturation of tailstemperaturemembrane solidify at low tempscholesterolonly in animal cells1 Tails and Fluidity Unsaturated not full of hydrogenmore fluid because phospholipids dont packed tightly
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