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Retired NBME 21 Answers

nbme21/Block 3/Question#28 (reveal difficulty score)
A 1-year-old girl is admitted to the hospital ...
Disruption of the secondary structure of collagen molecules 🔍 / 📺 / 🌳 / 📖
tags: biochem

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submitted by wasabilateral(47)
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I nkthi ti has shgmeotni ot od twih iclynge deu( to sti allms izse it anc fti in nmay elapcs ewher oehtr nomai dcisa acn not and nhece it ospivder crulr“utast sotc”nsempac ot eht la,nclgeo ..ie tup a nkki ni het lapah lh)i.xe If lnecyig is mespdaicl yb nhsgetmio ,eesl I ot’dn ihtnk a-lprenoolgc acn mrfo sti creorct sdnoaeycr turtrsuec.

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jotajota94  !urTe laso, ycgelni is 3/1 of cnleloag faal hnisc,a os ti saemk seesn hatt usttiionstbu iwth nlaneia whi(ch si umch grge)ib dwolu dlea to stpdiniuor in teh hlpaa lxehi to.finraom +2
jotajota94  r!eTu ol,as ygeicln si /31 of llanoceg aafl na,hsic so ti mskae esesn taht sibtuoittuns hwti elnaian hch(iw is humc gbegir) ulwdo elad ot sdtopinriu ni het palha exhli nmoofa.rti +
thepacksurvives  eyilGnc is smlla adn d,byen hhwic lwalso ti ot romf the blisrfi fro teh irtlep helxi +
brasel  Aslo ni lrganee FA( 8021 gp )50 OI si mrof beomrspl nmgrofi eth tlirep hilxe ihwhc is yeadcnrso ruuetscrt. Ftytlaoru,en hety geva su tsgeonihm ot oreasn wtih in eth snequtoi a;-)GlgAyl&t( +3
amy  Cna nemoeos elph em edutnradns why A is cicrrt?eno 02F02A agep :50 reiTpl lhxei fo 3 gclnoael a ansich si efmodr rmfo ollprcgneao vai rghdneoy nad diuleidfs .dobn sI tshi evyr samiril ot twha A si i Ac?.bgierdn Dereacesd -eohbgnyrdond tofmnario enbetew eolgalcn eo.csulmel +
umpalumpa  The oanelpitnxa gnvei by altbalwsraeai olcud work fi eht qestiuno dlouw ays tA&G;yla-lg- iut.onamt ,ewrvHeo hte qesnotiu astest ttah hetre is an ltl;-a&-yAgG m.atnitou +


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submitted by cellgamesgojan(43)
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I rdi,eguf ci--gelYyXn is ealcyncitlh rdcesdione a ampryir“ nmiao diac ursetcurt of a npt”roie nesic the nofdtiniie fo a rPimary uuertrcst of a noirtep si a“ rlneia aicnh fo iamno c”siad. fI oyu essm hitw the mryPira suute,rtcr as ni eth uenitsoq em,st oyu cnotan fmor teh Sdnycroae ceusrrtut of hte peirtn,o hhcwi si mrneiteedd by hte ngnoyog-rhndibed wihhc oucsrc eeewbtn hte dpeetip nokebabc, ndepnetdeni of eth R sgruop. I oeph stih dmea ss.een

Fomr wkdeipiia: roSnc“ayde ctrseurut si rloaymfl fniedde yb eth pnarett of rndhygoe snodb bwenete eth iaonm orehyndg dna rcbyolxa xynoge taoms ni eth pdeetpi kcabnboe.” heaiss(pm in)me

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From Molecular Biology of the Cell:

Biologists distinguish four levels of organization in the structure of a protein. The amino acid sequence is known as the primary structure of the protein. Stretches of polypeptide chain that form α helices and β sheets constitute the protein’s secondary structure. The full three-dimensional organization of a polypeptide chain is sometimes referred to as the protein’s tertiary structure, and if a particular protein molecule is formed as a complex of more than one polypeptide chain, the complete structure is designated as the quaternary structure.

https://www.ncbi.nlm.nih.gov/books/NBK26830/#A406

+5/- drdoom(1206)

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submitted by usmle11a(102)
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ok uysg nad i tuoeq ofmr r0osm4tew/.ccgptasis-.tsmet/p/e2pwenhiow/euasiltfcrholttso:/dreoe1ib

9"%0 aveh na dieitiblanfe nctigee itnmauot LOC A11 adn LOC A12
acseus marnalob alnlgceo slkingrc-isno avi a gelcniy usnbiitstout in hte alnrepglooc leceulom "

hchwi esnma htta IO hsa a necygil nuuiobssittt nad herferot sti bunlea ot rmfo a ceoyndars uucrr.stuet

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submitted by hungrybox(1277)
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ueD ot egycis'ln sllam s,ezi ti csetear kis"n"k ni teh imano icad cuneqse.e esheT knisk aer neeedd ot lrceocrty omrf hte dscnoeayr sterc.uutr

ehrtO :arnsesw

  • enke"awde eiaincrtont etwbeen glloeacn adn eolnt"rgoaypc - geollanc + rlteopyngcoa = .greclalati The qoesinut mtes omnetsin anym dstcfee in ONEb t(epy I )leagnocl utb on nmnioet fo esdtcef in cTaarWOgell ep(ty II geolnlac)
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submitted by basic_pathology(25)
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-lG-XyY si akobecbn rof llaneocg palha n.icah 3 celalong plaah inhcas alspri ot morf pertil l.exhi inylGce sah no R ,uorgp alglowni rof yxlltfieibi nad anifotorm fo ilpret xeihl. oN egincyl resevpnt hist oisnontuuc p,islganir tingpevner hte namtfroio fo aogclnel esdycrnao res.ucuttr

claeRl ttha -aslaleehhpci adn ets-tebesha rae emslxepa fo sanocryde sesr.utcutr Tsih acn eb hthugto of a otiaafisnment fo the palah eilh.x

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submitted by an_improved_me(91)
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rehtNoA ayw to gte ta ti si aiv nioiint:aeml

A. dronyehg inndbgo dultnwo lrlyea gencah nesic renehti nlaeani ron ienclgy rea Bpro.al lGy > Ala 'nsotdlhu enghac owh epnlior is ifidomde (I eanm it OLC,UD fi erteh wsa a ectsri dnehaircn or smohtn,egi btu ton a tgrea .ewsrDan) nhtgnio to eatcidin ttah ocleagln rigadeoentd is etraled in onpsrees to na AA nttoit.bsuius oslA, in teh tcxtnoe fo OI chih(w si het pintgeenrs cpo)na,mitl we elayadr ownk ahtt hte beolprm neost'd ehva ahgnynit to do tiwh eotg,aderdni roem hitw the nagceh ni fnruocinEucu/t ttres. nlseyoHt 'dont nkow.

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submitted by drdoom(1206)
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’eersH neo ywa to rcos-enf-ilmeposteia rsdae“eced r-bnynhgeodod fnr”otoa:im Im’ otn a gbi afn fo hist ilen of sin,neagor ubt ayclteclhni lnnaiea as a eids opugr ahs rmeo snyo*rdghe orf anpliotte gdyohenr bdnonig tnha yneclig:

lean:ain —CH3
lgnieyc: —H

o,S ynce“a,lth”icl enlanai duwlo mipetr moer dhr-nbnygeood oafirtn,om icwhh hmtig wlloa yuo ot liemainte htta hic.ceo

atTh aisd, it esesm mstola ebopissiml to leru out owhi(utt eryv antlceich gowlkened ro oems opidrevd minetreelpxa ata)d ahtt hte yltglihs lerarg anlniea osed ont mpiiar ghoredny noidngb beentew loegcaln elomlsuec aiv ictres iaa)(slpt ictrfe.nreeen nI mrspile emrst, inces nnlaaie si lraer,g ouy oldwu ihknt that ti smtu wmoohse frrieneet htwi the gnerddinghynob-o ahtt scrcou with hte yiwp-dlte cgyneil.

---
tSc*ltryi nsigke,ap sit’ tno eth eubnmr of nesyoghrd utb asol het thrtgesn of eht lieodp atth ltietaciasf dgyeonhr dng:onib a gnyohrde nudbo ot a gytosnlr calentoetveirge louceeml ekli onierflu liwl e”arapp“ emro eispoitv nd,a t,suh rhod-ngoynebd erom ysnotgrl twhi a eyrban ogxyne rdcemap(o tihw a ohgryned tcnencdeo to rboa,cn fro .a)pxemle

rtFehur :eadgrin

  1. l/.p:w/heedht.bdlndu/hcpp.mhelgim.sti/ds/otuehwcuuwqr
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hungrybox  Aeartcpiep eth erffot tub ihts si raf oto ognl to eb esl.ufu +30
drachenx  xobrughyn si a gnekfira rthae +
drdoom  c@hrnaexd haah, ,hna iomcgn abck ot tsih i razeile i was oarbylbp gv-gkreeoien llo +1
blueberrymuffinbabey  t'sin eth rgdehony ndbgnoi dpetednne on teh yodlaerdyhxt oipnrle dna i?eslyn so tath ltd'woun larley eb hte usesi rehe inecs tesoh tnrea' eht asa beign dltear?e +
drdoom  e@blbyrrue igndcrAco to srl’tbeA oCBM s(ee angTsten at ,trg)hi eyyxrihdsolyn dan doirpoxnlrheyy nbietucotr rgdeoynh sdnbo atth ormf nbeeetw the ahsicn aetnn,ii“rh(c” as ospeopd ot aiai-rcthn;n eht ,nhscia of r,esuco rae pasaeetr iydpseeopl;pt htta is, repataes eglcaoln ;orinepst nad tinerntaoisc btneeew epaerats naihcs east[prea ypdsplpeo]eit is hatw ew lcla ran“yuatrqe scrruu;et”t ese Tnaengt bovea.) dAn ni shti ce,sa sa uoy ptino otu, the stme ibdeescrs a A-ylg&tal;G tn.ibtsutuosi ahtT emses to neam otw ihng:ts ()1 eth teehr tapreaes ocgealnl dppseeltiypo lliw ont “akcp s]a[ g”yittlh ot omrf the lrtiep ehixl r=tua(qynear cu)ttrsreu we all nokw dan evlo adn (2) ponleir nsrig illw iafl to alyer iquet as ,yuslng mriocipsgomn eht cihalel nrocfaotimno htat dfiense na lapha inhca (sanerc=ody usc;rrttue het sepash ttah from ithnwi a glsine e)lpyei.dppot +
tadki38097  aslo oyu c'nat H onbd wtih b,nacro t'is ont larop eognuh +
amy  020FA2 0P5 s:ttae toafirnom fo rhcig(lowpoancelh si het rteipl ihlex cstu)terru aiv dnehgyro dna .uiliseddf oS A is trcneocir bc htree rea no ecolagnl lucoeselm tye (2dn turscuert hespapn ta aoloneprglc lvel)e +
drdoom  ym@a pitler hlxei si a ruarenayqt rtsuutcre siec(n tliper iexhl si a phsea htta froms EWBNTEE eserptaa ro a“tudl” pla/eoenllo-gcnoalrgc ).etidespp ,yPrmair oysdaencr adn yierrtta sturstecru rae isnetsdcorpi fo a nigsel .lpedypopite eOnc you ehva 2 or moer tpolsyipedep rtncnigeita twhi ehac orthe ,(ge.. nooelgmHbi lo)lemeuc yuo eahv raeynaturq uesttcru.r +

From Molecular Biology of the Cell:

Hydroxylysines and hydroxyprolines are infrequently found in other animal proteins, although hydroxyproline is abundant in some proteins in the plant cell wall. In collagen, the hydroxyl groups of these amino acids are thought to form interchain hydrogen bonds that help stabilize the triple-stranded helix. Conditions that prevent proline hydroxylation, such as a deficiency of ascorbic acid (vitamin C), have serious consequences. (Emphasis mine)

https://www.ncbi.nlm.nih.gov/books/NBK26810/#A3555

+1/- drdoom(1206)

From Molecular Biology of the Cell:

The primary feature of a typical collagen molecule is its long, stiff, triple-stranded helical structure, in which three collagen polypeptide chains, called α chains, are wound around one another in a ropelike superhelix (Figure 19-43). Collagens are extremely rich in proline and glycine, both of which are important in the formation of the triple-stranded helix. Proline, because of its ring structure, stabilizes the helical conformation in each α chain, while glycine is regularly spaced at every third residue throughout the central region of the α chain. Being the smallest amino acid (having only a hydrogen atom as a side chain), glycine allows the three helical α chains to pack tightly together to form the final collagen superhelix (see Figure 19-43).

https://www.ncbi.nlm.nih.gov/books/NBK26810/#_A3551_

+/- drdoom(1206)

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submitted by nmb29(0)
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I hitgm eb nkorvnihgeti ti u,tb H ndob itnooarfm fo aa's kseam het cdoyesran utcutersr of het oprietn ne(olaclg in ihts .)ecsa eTh Gyl ot Ala tsustonibiut sode tsluer ni lses H ondb tnmfar,oio btu fo iinuldavdi saa' nto eenwbet allegcon leleomsuc ta(ht itgmh be orme ofr rqnuraytea utsrtucer)

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lpp06  I khtni hte yek si ni eth senwar ,sginrhpa eth answer mtonenngii dbosH-n sysa nupt"rDisio fo bno-dHs weenteb egonalcl luushecmlghA"lt ooe oaleclng does ogrndue ogbid-nnH to ropuspt het ptirle ehi,xl shit si done hitnwi the same lcalogen kmnLoeucinl egi.l ereditffn aegollnc leluocsme urccso vai het inyels - hyeordsinylxy lksin edon ni eth MCE +1
kevin  hist is the oen nmmteoc thta nafyill hedelp me ntdunrsead why that was r.norcteic tahnk oyu +


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submitted by j123(16)
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yPamrir tcestruru = maion iacd ce esyaceonuqnrdeS rsteuruct = etstruruc ordemf ithw a isenlg noiam daci nqesuece (bate tdpalee ehtes, pahal lh,xie eT )aitterrcy cuetsrrtu = tlimplue casdneoyr struurcets entnacirigt tehegrot tmll(iupe ateb etalped etsesh skcadet no pot of heac hteo,r terayrecQna)r tu rteucustr = orepint retucrust rmfoed frmo dnofgil fo all aetirryt stteurscru to amke gndiibn se,tis .etc

incSe het anlniae was upt in laecp of eth e,Gynlci het mapyrri ttcrreuus saw belaun to fomr an aphal hlixe nicse lahap elxhi tecrurtssu ndee a artupalcir eeqcusen gyl( - -x y) in deorr ot romf rnyhdgoe bsodn ot epek eht ixehl leab.ts

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 -1  upvote downvote
submitted by unknown001(9)
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awht is aenollcg ? a oryedncas eropitn ecrru.ustt

whne yuo eremov c,yeglni het sotm aatbdnnu onima aidc , mfor teh rpesrrocu ucolmlee will yuo teg a pproer osadercny utecurtsr ? ON

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unknown001  egnoir hist +
drdoom  cna yuo r?aloaebte twhsa' rwgno thwi ouyr emtn?com +


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submitted by lilmonkey(63)
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Gly si aplr,o liennaA si anrnolop adn codyobh.iphr siMessne aevvrioesocntnn tiautnmo. esheT AAs eahv erfftedni mceialch rrtspoipee wcihh dale ot sdiurdept eonptir nilfdgo o(eradscyn t)uec.surtr iSailrm to luG - alV tinbiuttusos ni ecklSi lleC e.Dsiaes

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