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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 iktnh it sah eosnthgim ot do whti igeclyn u(de to tis asmll isze ti cna fti ni ynam clpesa rhewe herot omain sdaic nca otn nad hecne it erpodisv rus“aulttcr sctcn”oaepms ot eth lecl,ogna i.e. utp a ikkn ni teh hpala xl.e)hi If clengiy si slcaimedp yb gsnhtomei ls,ee I dto’n knhti nollpgorcae- cna form sti oertrcc nseacrdoy srtruetcu.

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jotajota94  T!eru olas, cnyilge is 3/1 fo nlaocleg alfa nc,ahis so it maesk ensse htta otsunttiubsi whit nalenia hhwic( si chmu ergib)g wdoul ldae ot pusrniiotd in het laahp hliex rmoan.tifo +2
jotajota94  u!eTr sal,o lniecyg si /31 fo ncoelagl afal sa,inch so ti skmea eesns that ssuotitutnib whit nainale cwh(ih si uchm )rbggei wuldo deal to iinoprtsdu ni eth lapah hliex tiaomnfr.o +
thepacksurvives  ecinylG si slaml nad yn,edb hichw awosll ti ot rfom het ifsrlib orf hte trleip xihel +
brasel  lAos ni anegler A(F 8201 gp 05) OI si ormf olsrpbem gmonrfi eht ltiepr elhix hwihc is deyarscno r.utsecurt elyat,rotnuF tyhe gave us oihsgmnet ot nsreoa tiwh in hte oqinsuet At;-(aGgly&l) +3
amy  nCa onomese elhp me adtednrnsu hyw A si cotcer?nri 202A0F egpa 5:0 lerTpi ihlxe of 3 colagnel a nchsai si eomdfr mrfo nocaprlelgo via dnryheog dna fddilesui obdn. Is htis yver larismi ot waht A si dib? irAe.gnc Daeedrsce r-yebnndoghdo tfnarioom eeebnwt lanloceg olsel.muec +
umpalumpa  eTh alxntnapoei gievn yb artaaleablwsi duocl rokw fi the qtnoueis ouwld ays G-ll&gyat-;A atoinu.tm reoH,vew teh neoituqs tstesa htta herte si an ;&gA-l-tyaGl mio.ntuta +


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 +13  upvote downvote
submitted by cellgamesgojan(43)
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I eugfdi,r ygle-Xn-cYi si naccleythli icdneedosr a mapyirr“ inamo cdai tuscutrre of a neprti”o nicse teh foeniiitdn fo a ryaiPrm trstceuru of a ponrtie is “a arelin hncia fo inamo i”s.dca fI you mess hwit eth myrPari rsr,uuttec as ni teh utqosein smet, uoy tacnon mfor eht ySoneracd sertturuc fo hte oitpe,rn hcwih is iednemdter yb teh hgriye-oddgnnnbo ihhwc crcosu bwnetee hte tdppeie bboeckna, dpeitdennne of eth R gpousr. I ohep iths amde sesen.

From idiweipka: dSaeyco“nr ecturrust is yrflaoml eienddf by hte nterpat fo gnodyrhe nosdb tneebew teh nimao nyrdehgo adn yorbacxl xengyo osmta in eth ppdtiee bknabeco.” peis(mhas )inme

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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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ko suyg nda i oeutq fmro 4//ec:/m.-t1tbthsswufweaismrnsheooogt0eritaietoe.ill2sc/dppctwpsre/o

%9"0 vahe an eiidntfaebli ceiteng amuitnto LCO 1A1 nad OCL 21A
essu ca maabnlro gcalnleo gcnl-snoikisr aiv a egilync bntttsiuoius in teh pogcnolaerl muleecol "

wchhi anesm atht OI sah a yicnleg oiittnusbsut nad roeheftr its aulebn to ofmr a rsaeycdno turucetusr.

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submitted by hungrybox(1277)
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euD ot yncglie's mlsal esi,z ti atserce ink"k"s in the nimao dica eeuescn.q eshTe nskik rea ddneee ot crryceolt omfr eht roecsnyad tects.uurr

Orthe :ersnwas

  • eeekand"w ntaoiiretnc tweenbe nlelgoac and otaog"eclnypr - lanloecg + trolanegcypo = agaliectr.l Teh nesouqti semt nmtonsei yman tfcdsee ni bONE pt(ey I e)lalogcn tub no tioemnn of tcfeeds in TlcarOegalW e(tpy II cglolan)e
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 +1  upvote downvote
submitted by basic_pathology(25)
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Yl-yG-X is bebnkoca fro lcelagon hapla hc.ian 3 elonlagc phala isacnh rslpia to form pertil e.ilhx iyeclGn ahs on R rg,uop anwgolli orf lftilbiixye and fnortmoai fo terilp hex.il oN ilyegnc speetnvr htis couuistnno ,sgiinpalr vrtgnpiene the iotmornaf fo aleglocn nycsdroea u.cttseurr

acleRl ttha hleais-plheca dan ha-ssebtete era alesexpm of drsnaocye ustrruetcs. Tsih can eb uhthgot fo a aittnaemfison of the aphal .hxeli

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 +0  upvote downvote
submitted by an_improved_me(91)
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oANreht way ot teg ta ti si aiv :mnnelotiiai

A. hngreyod dbiongn ulwtnod lylera ngehac cisne eerntih leinaan ron cieglyn rae .apB lor lyG ;gt& laA hldotsu'n hncega owh eirolnp is deifiodm (I maen it UOL,CD if etreh swa a srietc hiannderc or mgno,htesi tub ton a great en.aD)wsr hngtnoi ot aeictndi ttha laelgonc dtnodegeair si elrtdae ni epenssor ot an AA itbnsiot.sutu lo,As in the enxotct of OI hh(wic is eth gnrsteiepn cn)pioa,tlm we ldyaare knwo atht eth pobmrel t'dsneo ehva nhigntay ot od with ,rdtdgneaieo moer wthi eth cehagn in .cnrnroifEusu etc/utt teosnylH 'tndo kown.

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submitted by drdoom(1206)
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sreHe’ eno ywa to lstepemaocsfriin--oe ceddsrea“e r-nohdebydgno aior:”ntfmo I’m not a gbi fan fo tihs ilne fo ,rnsiegaon ubt lenhaccylit nnaleia as a dies ugorp sah rmoe egyn*hrosd for ttalpoein hongedry nbnogdi nath eycigln:

:annieal —C3H
iec:gynl H—

oS, lhn”y,lce“ciat innelaa owudl eimtpr ermo o-dengrybhdon amtr,fooin ihchw mgtih ollwa yuo ot lneiiemat htat h.ecoic

taTh idas, ti sesem stomla oiemispsbl ot reul uto ttohwi(u reyv hctlineac ogdekwenl ro some opdevrdi xpireletnaem data) thta eth lhgsytil erragl enialan does nto rimpai hreogndy bndniog eetnwbe lnocaleg lelesumoc aiv steric (lias)pat cenf.einerrte nI rispmle mr,ste scnei aenialn si l,gearr you uodlw tihnk ttha it utsm wsomoeh eernrtfei whit eth ern-nnidhbgdoygo that usocrc hwit teh -diyepwtl ynliegc.

---
*ytirStlc ,sngeapki ’ist ont het neurbm of ynrdohesg tbu alos eth thgrnets fo the opdiel hatt ctliifsteaa ryngoedh ong:nbdi a doegyrhn dnoub ot a ytrlsgno tctegiernoalvee lleumoec kile efurnilo will p“eap”ra omer eivotsip nda, t,hus dorgnnyodh-eb reom tglnyros thiw a anyreb gnyoxe adeocmr(p thwi a hrnyodge ocdentcen to orc,bna rof a)elpmxe.

reurFth edragin:

  1. dumslp.hi:hliu/gh.tqdeppe/.emewd.rlt/huhouwbd/cwcnts/
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hungrybox  eatAircepp teh tforfe tub siht si afr oto nolg ot eb se.ulfu +30
drachenx  ryxnuobgh is a ernkaifg erhta +
drdoom  chdxnr@ae ahah, ,ahn ncomig kbca to htis i eelaizr i aws albpbroy vigree-genko oll +1
blueberrymuffinbabey  sin't eht dhongyer bgndoni nnedpeedt no het ahyoxedrdytl ernploi dan ilnys?e os ahtt nutodl'w aeylrl eb the isseu hree cesin sothe ean'rt het saa ebgni eel?tard +
drdoom  ulrber@eyb idAoccgnr ot tAels’br oCMB (ees nnsTateg ta hr)tgi, xesinyrdhyloy adn xeodnrilrphyoy ertcitnbuo renhgdoy bdson tath romf bnewete het hanics t,“h”cne(riani as sdopoep ot ni;irahtcan- teh hnis,ca of ourecs, aer saterepa oyltpdesip;ep ttah ,si apreaste cnleoagl tosnirep; dan eiacnsotrnit benwtee tapersae iscanh ap[eesart otpepeysd]pil si thaw we clal eurqtyaa“nr ruus;rcett” ese nTetagn eoavb.) dnA in tshi ,ecas sa ouy ntopi t,ou teh etsm cdssebrei a ;tGyl-Ag&al ntistuoi.btsu htaT esesm ot mnea two :gnhsti ()1 het etreh paeresat eglcoaln depstipyelpo ilwl ont cp“ka s][a ylihgtt” ot romf teh eitlrp lexhi yutr=qe(naar ercuts)rtu we lal wkon nad eolv and )(2 enplroi nisgr illw fail ot lreay qteiu sa gyu,lsn pgmiormnsioc the aiclhel amrtoonfnioc ahtt idefens na aahpl inhac an=o(syrcde suctreut;r eht sehpsa htat mrof tiiwnh a eginsl lyopi.dpt)epe +
tadki38097  salo you tacn' H dobn htwi crbno,a its' otn proal hugneo +
amy  02A2F0 P05 e:stta torfamnio of (ropcehhnliogclaw is eht pretli hlexi setut)urcr avi nhdoyger dna fiduesld.i So A is eonirrctc cb ehetr rae no lencoalg luoelsemc yte (n2d rurutstce hepsanp at elcloponrag l)leve +
drdoom  my@a ritlep xhile si a qrrntyaeua rcuutster niecs( iplert helix is a pseah ttha rmofs ETBWNEE apetsera ro lu“d”at og/elepolncraaocln-gl spepe.dt)i airrm,yP oceydsran dan eatryitr eutstsurcr rae sprioisncetd of a gesiln ppledietpoy. enOc uyo ehav 2 ro emro epidleoyptsp niitcngeart hwit ecah eotrh eg,..( oeogbmlinH emo)ecllu oyu haev trryquaean rceuttsr.u +

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 ithmg be inveniohgrkt it ,btu H nodb formianot of aa's saemk hte yodeascnr uuterrtsc of eht otienrp gll(cnoae ni sith ).ecsa Teh lyG to laA onbiustituts eosd ursetl ni essl H obdn orofam,tni tub of dilnaidiuv s'aa ont beneewt lecnaogl ocmlelues tht(a itgmh eb emro fro ruantreyqa tr)uersuct

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lpp06  I ikthn eth yke si ni eth nwresa ighn,arsp eth raewns mnnioetngi d-osHnb yass oui"tspDrin fo s-bndoH weeetbn leancgol echthme"llosgulA uo nelacgol dsoe rngodeu dnHgobi-n ot opsrtpu eht telrpi l,ehix ihst is edno wtniih het meas gnllaoec u onlikgcnme.Liel ftnrfieed alcgenol ocsmleuel csorcu iva hte senyli - yiyxnsheoldyr lknis enod in het MCE +1
kevin  tshi si eth one mtcmnoe taht linafyl dlehep em aensrdudtn yhw atht was icrtce.nro ahktn uoy +


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submitted by j123(16)
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irPmray usrrteuct = noiam cida n ccqSuseoeydreean urctsuret = cutreruts reofdm hwti a lnsige naoim ciad seeeqnuc (btea epealtd ethse, apalh lx,hie ri ce)Ttryate eurustcrt = ituepllm reoadcysn cttsruurse cnigetnitar eegrthot m(itlepul abte plaedet hteess kecsdta on tpo fo aech tr,eho rtern)ru tyQcaae urcteusrt = inpotre truseucrt reofmd form fognidl fo lal yrtariet uttcreusrs to aekm ibdngin etiss, tce.

Sceni hte ninalae was ptu in lpcae fo eth yniG,cel the prmriya rrsetctuu was laneub ot orfm na hpala hexli nicse laaph liehx scttresruu need a raariupltc seequnce gyl( - x- )y in dorer ot form neyrodhg bnsod ot pkee eth lihxe .tesalb

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 -1  upvote downvote
submitted by unknown001(9)
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thwa is glenloac ? a dreosyacn oinprte .stcuretru

enhw you ermveo ygli,cne het tmso dantanub oaimn idca , ormf eht rcrrpseou oecluelm lliw oyu tge a prpeor sodnrecya sututrecr ? NO

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unknown001  rgeino thsi +
drdoom  anc uoy tbearal?oe a'htsw gnorw itwh uoyr eton?cmm +


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 -4  upvote downvote
submitted by lilmonkey(63)
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yGl is rolap, nlnaAie is naoolrpn dna hhpoibryd.co seensMis vvasceneoinrnot a.miuontt eeTsh AsA hvae ftrnefdie hcilacem troespprie hchwi dlae to siruddtpe penorit fginold ydo(enacsr .trecutsu)r liariSm ot lGu - laV stubtsintuoi ni ekclSi Clle De.isesa

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