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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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 +16  upvote downvote
submitted by wasabilateral(47)
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I tnihk ti hsa shogmntie ot od wthi incelgy du(e to sti slmal esiz it cna tfi ni aynm slpeca wehre tehro nimao siacd nac otn nda ehcne ti orvideps “ucrutlsrta epc”mcstason to teh longe,lca .ei. put a nkik in eth ahpal el)hix. fI gceinly is smlapdiec by itohesnmg ele,s I o’dnt nihtk gpcleo-lanor acn ofmr ist terrcco cesrnaoyd utcrteur.s

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jotajota94  ure!T sl,oa gnelciy si 1/3 fo ocanlelg alfa ish,nac so it emska essen taht sotusbinitut ihtw naeinla iwh(hc is mcuh iegg)rb louwd leda ot itnopdrusi ni het alpha xlhie mftnor.aio +2
jotajota94  !rTeu a,lso enigycl is 13/ fo agocenll alfa nc,siha so ti amsek esesn atht bousntstuiti twhi aaielnn (hicwh si mhcu r)iegbg odulw elad ot srotnupidi ni eth alhpa lehxi oaoi.tnmrf +
thepacksurvives  ilGeycn is llmsa adn n,ebyd hihcw loswal it to ormf eht sbilrfi ofr het lrtpei xheli +
brasel  Asol in realgen FA( 2810 pg 0)5 IO si mrof olmerspb ronfmig het iplrte eixhl hicwh si oencadsry .rtcrustue lraetytunF,o hyte aveg su imgoetshn to easorn tiwh ni hte isqtenou aGl&A;-(lg)yt +3
amy  naC eoneoms elhp me nrdetnsdua hwy A si rcetc?roin F20A02 epga 5:0 ileTrp helxi fo 3 aelnclgo a nashic is mfeord omrf ocgponlaelr aiv nohredgy and siediludf obd.n sI isht vyer irslmai ot ahwt A si ei i.ngAbdcr? Deeeracds eynnogdhbord- omifoarnt eenbetw elcglona ulo.ecelsm +
umpalumpa  eTh etnoapnlxai neigv yb atlrbaiwaasle cdlou okwr if eht uieoqnst wlodu ysa g--&;lytlAaG monat.uti vHee,owr het teiqusno stsate taht ehter is an Gl-l&Ay;gat- t.muoatin +


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 +13  upvote downvote
submitted by cellgamesgojan(43)
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I ifrgud,e in-ly-XeYcg si teyccilalnh secoedndri a miryra“p nomai cadi uttecsrur fo a ”tpienor niesc eth notiiendif of a mayirrP suetrruct of a reionpt is “a leinra ciahn fo oiamn adc”si. If ouy ssme itwh hte irymarP tusu,crert as in teh qeinuots m,tse you nacont rofm eht odnrcySea tsrtrucue fo teh ortepn,i hciwh si iedretdemn by hte enhdirogdn-yognb whcih crsuoc eewntbe the tedeipp cbeonbka, dnpenedteni fo hte R o.rgsup I ohep stih amde .ssene

mrFo iakweidpi: Sr“ndocyae crtruseut si loramfyl edeifnd by hte earnttp of engydhor dbsno tewbene teh minao egdrnyho and rbyxolca xgnyeo samto in hte pdpieet abbkeocn.” shseai(pm ie)mn

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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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 +4  upvote downvote
submitted by usmle11a(102)
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ok sygu dan i etoqu ofrm /oic2:teshlswa.wslpsrmfero-ts/isuca/ntopdoptr1itebe/o4e.wt/igcmthe0e

"9%0 ehva an ieailtdnbeif icenegt mtntiauo OCL A11 nda OLC A21
cassue aalnmobr oalglnec ok-sgrniinslc iva a nyieclg ossubtitntui ni eth cngolpaorle lcmeoule "

ihcwh emasn thta OI has a ceigyln stbitustouni dna rfhtoere tis bluean ot from a dnaoyserc crst.euutru

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 +4  upvote downvote
submitted by hungrybox(1277)
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Deu ot sylei'ngc lsalm i,sze it streeac "nsk"ik ni teh moani iadc ceeq.uesn eTshe kiksn rea deeedn ot rlrectyco rmof teh cseydraon srtet.uruc

Orhte sas:enrw

  • wneaek"ed aneirttnoci wtneeeb gclnloae adn loypgoa"ncrte - onalcelg + poloractyegn = etga.rilcla The qotenusi emts osnenmti anym ecsefdt ni ENOb ytp(e I eclgn)lao tub no moenint fo ecefdts in laaWrclTgeO y(tpe II )aelcgnlo
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 +1  upvote downvote
submitted by basic_pathology(25)
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XlG--yY si banekboc rof glaoenlc lpaha a.cihn 3 glnceloa apalh iascnh aslrpi to fmro trpeli ixhel. eylnGci sah no R ugp,or ilwonagl fro tliielfbyxi nad rmotnfoia fo ltirpe .exhli No incygle sentpver isht nsctuooniu pginlri,as npreegintv het aimortofn of alecnlog nerodycsa .sretcrtuu

eRlcal ttah ecahhi-lspeal adn heta-btsees aer xemaspel fo asnrdycoe r.rcsttusue shiT can be hugotht fo a fmtiainnaoset of hte alaph ehxl.i

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 +0  upvote downvote
submitted by an_improved_me(91)
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etNorhA ayw ot egt at it is iva eianl:omntii

A. rndgehoy nbdonig ldwtuon llryea achgne iecsn erineth naaneli orn lneyicg era porBal. ylG &;tg alA ns'ohdutl hcngae how nelorpi si dmidofei (I aemn it L,UCOD if ereth saw a rsetic anrnhdcei ro hmongis,te ubt not a gtera .)aDsnwr e nihntog ot ieniatcd ahtt olncegal etoagedidrn is aerdtle in eoprsesn to na AA tstsuniiu.bto osAl, in hte ttoncxe of OI w(hcih si eht nspegnreti nl,o)pmaict ew laaryde nkow atth teh bopmrle toed'sn heav nnagthyi ot od with d,deoertgain rmoe with the hcnage ni ncentctustrEi.of /uru steoHynl o'tnd .knwo

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submitted by drdoom(1206)
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eHser’ noe ywa to aeon-ipsrco-eeflismt ed“sarcede -gdnhyorobden faot:no”imr m’I not a gbi fna of sthi ienl fo ei,gnaosrn but hillacycent nlineaa as a isde group ahs orme ry*hsdonge fro liaptteno odenrhyg nbnodgi thna icgnyle:

eaai:lnn 3C—H
iy:cngel H—

,So “”nllc,tihacey nalanie duolw tpmrie eomr bo-oehgynrdnd atimfnoor, cwhhi gimht oalwl yuo ot tnimeaile htta cci.oeh

aTth di,sa ti eemss moalst eomsislpib to urel tuo h(utoitw veyr clatnecih eodgkweln ro msoe rviodped ieexlrpeatnm d)aat thta het lhtyisgl reglar liaenna esod nto mriiap droehyng nbngdio ebentew nelgoacl lcsleomeu via ecitsr asa(i)lpt fice.rnteener nI emlpisr ms,ret seinc elanani is e,arlgr uoy uwlod hntik atth it umts omsoewh fenierert with eht hdnid-oebgryonng that srucoc wthi het ilwy-pedt igeyncl.

---
irtlcS*yt kpi,segan ist’ nto het mrebnu fo hydeognrs btu laso teh gsethntr of hte lpdoie atht ifaitseatlc ehodrngy gnb:doin a goehrynd bondu to a gtlnosry ieeeortevgalnct eolulecm kiel neliourf liwl “arep”ap emor tvipoesi nad, ,suht hndderynbo-go remo nogtsylr iwht a rayben gonxey dcae(romp htiw a yrhdneog noeeccdtn ot abrocn, orf )mepael.x

rthueFr rae:nidg

  1. h.bthls/cep.idm.slq.wwrohp/:mgeitdhpe/eduldt/unwcuh/u
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hungrybox  peiaArpcet eht otffer but tihs si rfa oot lgon to eb eusufl. +30
drachenx  yrxgnubho si a negaikrf ertah +
drdoom  c@nxaehdr aha,h ,anh gcnomi kabc to iths i zearlie i was olbbapry vonkegreegi- llo +1
blueberrymuffinbabey  'ntsi the gernhydo odinnbg peedentnd on the ryltdyxheoda ernpoil and yile?ns so ttha uon'dwlt lrealy be eth uessi rehe ciens thseo renat' teh asa bgnie atd?lere +
drdoom  be@rblyure codcArnig ot esltb’rA MBCo see( tangsTen at ti,rh)g royyyndleihsx nda rdxnirloehoypy eoibutrcnt edornygh ndbos atht fmro eetnewb het hnscai “ia”tcheni,(nr sa dopspoe ot -traniahcni; eht icnah,s fo ec,osur are seeatarp sopley;ptpide ttha s,i apreaste gnoaellc eo;trpnis nad ntcanesiotir webenet prataees hiacsn tpe[saear s]tipoppleyed si ahwt ew clal rqarnyat“eu uet;rutrcs” ese gentanT avoeb.) dAn ni hist sa,ce as you oipnt uto, eth tsem rdsseebic a lgy;Aat&-lG untbuistoti.s tahT smees ot enam owt gth:nsi (1) hte rtehe psareeta gaenlclo eptiolpdepys lwil ont a“pkc ]s[a t”ygilth ot rmof eht ietlrp hxile aqyen=ruat(r ts)terruuc we all kown nad elvo and )2( ilenrop gsnri wlil ailf to arley qitue sa u,gysnl scgpnmirmioo eht hcaiell mcrotfoinano thta dfsinee an laaph cihna sacey(drn=o srcteur;ut het esaphs htta rmfo tinwih a elinsg ptyeodp)ie.lp +
tadki38097  alos oyu c'tan H dnbo tiwh nb,caor i'ts not olapr ngeohu +
amy  20F0A2 P50 sa:tet atirmoofn fo (lnlhogcpiwhecrao is the rlptei lxihe eusucr)ttr iav horgnedy dan d.lfeiidus So A si tecrrcnoi bc hetre ear no lenaclog cuslmeoel eyt (nd2 tsrrctueu ahppsne ta nolaelcgpro lev)el +
drdoom  my@a reltpi xilhe is a ynureqtaar sutrurtce e(csin ileprt hxiel si a hseap htat rofms WTBEENE esaarpte or ”ua“ltd goerlllpng-nl/coaoeac ppeti.se)d riyrm,aP dnaysecro adn ytirrtae cestruusrt ear oipcdtressin fo a nslige .depeptloipy Oecn uyo veha 2 ro meor tippsldeoepy rgtnatiecin hwit chae thore e.,.(g lHienomobg )uelocmle oyu haev aueqartnyr userc.ttru +

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 himgt be gnkienhrotiv ti b,tu H dbno riafotmno of s'aa emaks het dsnoecray trsrutceu fo eth oeritnp anc(olgel in ihst ecas). heT ylG to Ala istnbuoustit dose ltrues ni lsse H dobn o,rtfomian ubt fo idnvluiadi a'sa tno etenewb aogellnc scelumelo tat(h ighmt be orme rfo naqrtuyaer eutsurrct)

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lpp06  I inhkt eth eyk si ni the wenars s,anpigrh eht nsaerw tningeonmi dHnbs-o yass snD"oriupti of ds-onbH eewebtn elnoaclg hosAl"gchuulletome goalnecl sdoe gudrneo inoHb-gdn to psroput eht itrple ,lhixe hits is oend ntwiih teh emsa locnealg .ikLn minculegelo fedetnfri onalcgle sullcmeeo ucsorc iva het nyseil - iryxnesohydly inlsk oned in hte CME +1
kevin  tihs is het noe cmtonme ttha ilflayn hedlpe me nsrdeudtna yhw ahtt swa cein.ctrro hnakt uyo +


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submitted by j123(16)
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rrmyaPi ctursteur = oinam dcia cSqeoncu ynseedera suttrrecu = ruretutsc odemfr with a glines oanmi ciad quneesec be(at taedlep he,set hpaal lxhe,i retTt craie)y rcrtesuut = tlmepliu coydanser uscuetsrtr ecngiainrtt hgttreeo (emtlpuli beta pedtael esehts acktsde no tpo fo heac hreot, crraeat) Qurntye rusuectrt = pnetroi srrettuuc rfemod ofmr ngfilod of all trreayit teursturcs ot make ngnibid esist, ec.t

eincS hte aielnna wsa put ni pealc of hte clnGe,iy eth pyirram rrtecusut aws anlbeu to from na aphla heilx einsc pahla ihxel utrrtussec dene a aipurarltc neqeeusc (ylg - -x y) in rreod to orfm yrgdeonh sbdno to epek the xlehi sbl.eta

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 -1  upvote downvote
submitted by unknown001(9)
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tawh si ceangoll ? a dayersnco itnoerp rtesr.ucut

nwhe yuo evrome ciy,egnl het tosm bnntadua oiman cadi , mfro het soupercrr emleuocl iwll you gte a erropp eoycandrs ttrreusuc ? ON

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unknown001  rieogn shti +
drdoom  nac yuo lebraao?et tha'sw rogwn thwi yuor omt?necm +


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submitted by lilmonkey(63)
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Gly si pr,aol nenAail si noprloan dna yd.obhhiropc eiesssMn asonintrneecvov aoittunm. sheTe AAs aveh fndietefr imclhcae otsieeprrp chwhi edla to dptdrusei tiprneo lgiofnd cna(esoryd )rtsuterc.u railSim ot ulG - lVa tittubsosuni in eclikS leCl Daesise.

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