Lecture 9 Cell Structure – Membrane Structure and Function

Lecture 9 Cell Structure – Membrane Structure and Function

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Lecture 9 Cell Structure – Membrane Structure and Function A. Structure - Phospholipoprotein membrane - Fluid mosaic model Phospholipids and proteins do not have to be stationary, they can move across the membrane 1. Membrane lipids (fig. 5-2) a) Phospholipids Glycerol Three carbons, three alcohol groups, the rest hydrogen 2 fatty acids ester bonded to the OH groups (every bend is a CH2) Phosphate group attached to third OH group, attached to an R group (alkyl) b) Hydrophobic - Tail - Non-polar - Not water soluble c) Hydrophilic - Head - Polar - Water-soluble d) Amphipathic - Water-soluble portion and non-water-soluble portion - Soap molecules Form a cylindrical structure - Cell m e m brane Formed by a lipid bilayer
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Takes the least amount of energy One polar end faced inside the cell, the other polar end faces outside  e)  2-dimensional fluid (fig. 5-4) - Cannot make the bilayer flip back and forth f) Cholesterol (fig. 5-6) - Only animal cells have cholesterol (not bacteria or plants) - Cholesterol is not a fat or oil, it’s a lipid (steroid) - Cholesterol is non-polar, so it is located between the lipid bilayer It acts as a spacer, keeping the fatty acids separated If it wasn’t there, the fatty acids could solidify in cold temperatures Keeps them more fluid 2. Membrane proteins (fig. 5-6) a) Integral proteins - The protein is actually IN the membrane - Attached to the membrane itself Either goes all the way through (transmembrane proteins), or may be  attached to one side or the other Integral proteins CANNOT BE REMOVED, the phospholipid will be  b) Peripheral proteins - Not attached directly to the membrane - Usually attached to the integral proteins A non-covalent attachment (easily removed, weak attachment) c) Functions (fig. 5-10) - Anchor cells Called integrins Extended out from the cell membrane
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Help anchor proteoglycan to the cell - Receptor proteins – signal transduction
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This note was uploaded on 05/30/2008 for the course BS 130 taught by Professor Smith during the Fall '07 term at University of the Sciences in Philadelphia.

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Lecture 9 Cell Structure – Membrane Structure and Function

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