Lecture 3- cell membranes


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Unformatted text preview: & and&the&interior&parts&must&be&hydrophobic!&that&ways& proteins&could&sit&happily&in&the&membrane 10 Membranes are fluid • Membrane molecules are held in place by relatively weak hydrophobic interactions • Most of the lipids and some proteins can drift laterally in the plane of the membrane !Membranes"are"as"Mluid"as"olive"oil !If"they"Mlip!Mlop"hydrophobic"tails"must"be"out"in"the" presence"of"water"and"they"don't"like"that"(Mlip"Mlop"is" rare) – rarely flip-flop from one layer to the other 10:25 11 • The lateral movements of phospholipids are rapid • Many larger membrane proteins move more slowly but do drift. – Some proteins move in very directed manner, perhaps guided/driven by the motor proteins attached to the cytoskeleton. – Other proteins never move, anchored by the cytoskeleton. – 2 microns per second. !Labeled*proteins*on*the*surface*of*each*of*the*2*cells* with*+lourcent*dyes !Human*cell*(*red) !Mouse*cell*(green) !Fusion*between*the*human*cell*and*mouse*cell*and* discovered*that*the*two*distinctly*coloured*proteins* began*to*mix !Within*40*minutes,*the*colours*had*completely* Fig. 5.2 intermixed*on*the*fused*cells !Proteins*which*were*labeled*were*able*to*travel*around* 10:25 12 the*+luid*membrane*after*time*elapsed 4 !Saturated"fat!"carbon"after"carbon"after"carbon"with"2" hydrogens"on"each"end!"all"the"carbons"are"bound"to"the" • Membrane fluidity is influenced by temperature and by its constituents. • Cooling, membranes switch from a fluid state to a solid state as the phospholipids are more closely packed. • Membranes rich in unsaturated fatty acids are more fluid that those dominated by saturated fatty acids max"number"of"hydrogen"atoms !Unsaturated"fat!"pull"out"a"hydrogen"and"allow"a" double"carbon"bond"!the"presence"of"a"C!C"double"bond" imparts"a"kink"or"bend"to"...
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This note was uploaded on 02/11/2014 for the course BIO 1202B taught by Professor Almanke during the Winter '12 term at UWO.

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