Lecture 3- cell membranes

In this fluid mosaic model the hydrophilic regions of

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Unformatted text preview: "(not" actually"a"membrane) 10:25 Gardiner 2013 Fig. 5.5 7 !Which"structure"forms"depends"on"the"phospholipid" concentration !Polar"hydrophillic""heads""are"in"the"aqueous"solution" (associate"with"water) !Nonpolar"hydrophobic"fatty"acid""tails""are"not"in"the" aqueous"environment !This"positioning"occurs"due"to"the"hydrophobic"effect!" the"tendency"of"polar"molecules"to"exclude"hydrophobic" molecules - Freeze Fracture- freeze cells in liquid nitrogen and use a sharp knifes edge to fracture the cells by hitting them HOW WILL WE STUDY MEMBRANES? - The cells break along certain fracture lines (usually inner and outer halves) which tend to be where the phospholipid tails are - Breaking the cells exposes the membrane interior - End up with 2 surfaces- one with bumps, one with concavities that match the bumps - Individual particles the size of proteins are embedded - The particles visible in the expose membrane interior are integral membrane proteins Fig 5.3 - MEMBRANE ASYMMETRY- provides evidence that the two sides are distinctly different. The membranes proteins found on one half of the bilayer are structurally and functionally distinct from those of the other half 3 • In 1972, S.J. Singer and G. Nicolson – model that proposed that the membrane proteins are dispersed and individually inserted into the phospholipid bilayer. – In this fluid mosaic model, the hydrophilic regions of proteins and phospholipids are in maximum contact with water and the hydrophobic regions are in a nonaqueous environment. 10:25 Gardiner 2013 !Proposed&that&proteins&are&embedded&in&a& phospholipid&bilayer !Suggested&that&the&exterior&parts&must&be&hydrophillic...
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