• Exam%3%will%be%held%Friday,%Nov%13th%in%the%Tes:ng%Center%Arjona%110%• You%must%sign%up%for%an%available%Ex am%Slot%on%HuskyCT%Exam%Registra:on%Link!%!• Exam%slots:%12:00-1:30,%1:30-3:00,%3:00-4:30,%4:30-6:00;%there%is%no%regular%class%on%exam%day.%• If%you%have%another%class%conflict%w ith%the%available%slots%you%must%provide%a%scr eenshot%of%your%UConn%schedule,%and%contact%me%ASAP!%• HuskyCT%Materials%will%be%unavailable%online%on%Friday.%Be%sure%to%download%any%materials%you%want%if%you%plan%on%last%minute%studying!%%• There%will%be%2%Review%sessions%before%the%Exam.!• 1.!Wednesday,!11/11,!6-8pm!TLS!154!• 2.!Thursday,!11/12,!6-8pm!BPB!130!• Bring!your!Problem!Sets!!• The%early%exam%for%people%with%legi:mate%reasons%that%have%been%cleared%with%me%will%be%on%Thursday,%11/12%1:30-3:00pm,%BPB%201.%• If!you!need!to!take!the!early!exam!for!a!legiImate!reason!and!have!NOT!contacted!me!yet,[email protected]!• Students%who%have%CSD%Exam%:me/place%accommoda:ons%will%be%taking%the%exam%at%the%CSD%office.!Please!get!any!Exam!AdministraIon!Forms!to!me!ASAP.!Exam%3%will%be%held%Friday,%Nov%13th%in%the%Tes:ng%Center%Arjona%110%Exams%will%use%Respondus%LockDown%Browser:%1.!Locate!the!“LockDown!Browser”!shortcut!on!the!desktop!and!double-click!it.!2.!Login!to!your!Blackboard!course.!3.!Navigate!to!the!test!and!select!it.!4.!A!new!window!will!appear!asking!for!the!Exam!Password.!!5.!Enter!the!password!and!click!Begin!Exam!6.!The!test!will!then!start.!!!NOTE:!Once!a!test!has!been!started!with!Respondus!LockDown!Browser,!you!cannot!exit!unIl!the!Submit!buOon!is!clicked.!!%Intermediate%Filaments%and%Sep:ns%%D.Drubin!•!acIn!filaments!•!microtubules!•!intermediate!filaments!•!sepIns!The%cytoskeleton%consists%of%at%least%%4%polymer%systems!Today:%%Structure%and%Func:on%of%%Intermediate%Filaments%and%Sep:ns!1.!Are!~10!nm!in!diameter!(intermediate!between!acIn!!!!!!thin!filaments!and!myosin!thick!filaments).!2.!Are!very!stable!–!disassembly!in#vitro!requires!treatment!!!!!with!agents!that!denature!proteins.!!3.!Do!not!bind!nucleoIdes.!!4.!Are!non-polar!in!structure.!!5.!Can!withstand!stretching!forces.!IFs%share%5%basic%characteris:cs%Intermediate%Filaments%(IFs)%are%strong%rope-like%polymers%of%fibrous%proteins%that%re sist%stretch%%Intermediate!filaments!play!a!structural!or!tension-bearing!role!in!the!cell!and!are!important!for!cell!strength!and!cell-cell!aOachments.!Intermediate%Filament%structure%IF!proteins!have!a!central!α-helical!coiled-coil!rod!domain!that!is!highly!conserved!and!heads!and!tails!that!are!variable!in!length!and!sequence.!!They!form!a!parallel!dimer!that!assembles!into!an!anIparallel!tetramer.!Tetramers!assemble!end-to-end!to!form!protofilaments,!which!associate!laterally!to!form!protofibrils.!!Protofibrils!further!assemble!into!an!IF.!!Because%the%tetrameric%subunit%has%no%polarity,%the%filament%has%no%polarity.%%Figure 16-19 Molecular Biology of the Cell (© Garland Science 2008) Assembly%of%IFs%in%cells%Soluble!tetramers!can!be!isolated!from!cells,!suggesIng!that!this!is!the!basic!building!block!of!the!filament.!!The!soluble!pool!of!IF!tetramer!in!the!cell!is!very!small:!1-5%!of!the!total!intermediate!filament!protein.!(In!contrast,!~40%!of!acIn!is!present!as!monomer!subunits.)!!There!is!slow!exchange!of!the!IF!subunits!with!the!insoluble!filaments!in!the!cell,!the!dynamics!of!these!filaments!are!very!modest!compared!to!acIn!filaments!and!microtubules.!Intermediate%Filament%incorpora:on%assay:%Kera:ns%incorporate%thr oughout%the%filaments!Total%Kera:n%(an:-kera:n)%Injected%Kera:n%(an:-bio:n)%Total%microtubules%(an:-tubulin)%Injected%GFP-tubulin%Microtubule%incorpora:on%assay:%Tubulin%subunits%incorporate%at%growing%+%ends%D.Knecht!(minutes!later)!1.%Type%I%(acidic)%and%Type%II%(basic)%Kera:ns.%These!form!heteropolymers!composed!of!acidic!and!basic!subunits.!There!are!over!20!keraIns!expressed!in!human!epithelial!cells.!KeraIns!are!found!in!epithelia!that!line!internal!body!caviIes.!Because!different!cell!types!express!different!sets!of!keraIns,!the!origin!of!epithelial!cancers!(carcinomas)!can!be!determined!based!on!the!set!of!keraIns!found!in!the!tumor!cells.!There!are!also!about!10!‘hard’!keraIns!that!are!found!in!hair!and!nails.!KeraIns!in!the!outermost!layer!of!the!skin!become!cross-linked!together,!and!as!cells!die!the!keraIns!persist!as!a!protecIve!layer.!!2.%Type%III%Vimen:n%and%Vimen:n-related%filaments.%These!proteins!can!form!homopolymers!that!consist!of!a!single!IF!protein!species.!Vimen:n!is!the!most!widely!distributed!intermediate!filament!protein.!It!is!found!in!fibroblasts,!endothelial!cells,!white!blood!cells,!and!embryonic!cells.!Another!type!III!protein,!desmin,!is!found!mainly!in!muscle!cells!where!it!links!adjacent!Z-disks!of!myofibrils.!Glial!fibrillary!acidic!protein!(GFAP)!is!a!vimenIn-related!protein!found!i n!th e!glial!cells!that!surround!neurons!and!astrocytes.!3.%Type%IV%Neurofilaments.%These!are!composed!of!heteropolymers!of!NF-L,!NF-M,!and!NF-H.!They!are!found!in!axons!and!are!important!for!providing!strength!in!the!axon!and!determining!its!diameter.!4.%Nuclear%Lamins.%The!nuclear%lamina%is!a!meshwork!of!IFs!that!lines!the!inner!surface!of!the!nuclear!membrane.!It!is!composed!of!lamins%A,%B%and%C.!Nuclear!lamins!differ!from!other!IF!proteins!in!that!they:!have!a!longer!central!rod!domain,!contain!a!nuclear!import!signal,!assemble!into!a!two!dimensional!sheet-like!lalce,!and!are!more!dynamic!than!other!IFs.!Disassembly!of!the!nuclear!lamina!during!mitosis!is!mediated!by!phosphorylaIon.!Types%of%Intermediate%Filaments!Types%of%Intermediate%Filaments!Table 16-1 Molecular Biology of the Cell (© Garland Science 2008) Types%of%Intermediate%Filaments!Intermediate!filament!binding!proteins!(IFBPs)!cross-link!IFs!into!networks!or!bundles.!The!network!of!IFs!in!the!cell!is!omen!coincident!with!the!microtubule!cytoskeleton.!In!some!cell!types,!disrupIon!of!the!microtubule!cytoskeleton!with!microtubule!de-stabilizing!drugs!causes!the!IF!network!to!collapse.!!!Nuclear%posi:oning%and%support%of%the%nuclear%envelope.!IFs!such!as!vimen:n!typical
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