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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 knith it sha eghstmino to od hwit yneiglc ud(e to tis lmsla zeis ti acn itf in amny asclpe hewer hteor aniom iadcs can tno nda eehcn ti droviesp ctutsl“uarr naoce”pmstcs to the nlco,glae .i.e upt a knki ni the lapha x.hi)le If elgciyn is cepaidsml by sgmehntoi ,eles I td’on ihtnk aocrnogl-elp acn ofmr tsi rceocrt nscryeoda uteurrs.ct

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jotajota94  T!eru ola,s engcily si 1/3 of olanclge flaa h,isnca os it mseak eesns taht itnuistuostb tihw naenila (ihhcw si humc ibg)reg udolw elad to riitpunosd ni teh aphal xihel foiamnro.t +2
jotajota94  Ture! lso,a glecnyi is /31 fo acnoelgl aafl ahc,ins so ti ksmae enses taht tstuunibisto with alnneai whhic( is uhcm egibr)g udlow edal ot iuprisntod in teh ahalp ehxli mrfi.taoon +
thepacksurvives  nieylcG is mslal and ,ebndy ihcwh lowsla ti ot rmof eth sbflrii fro hte epltir ehxil +
brasel  Aosl in leenrag (FA 0812 pg )05 IO si rofm erbslomp rimnofg the etplri lehxi chiwh si saydncore tcert.urus etoaltFnyu,r htye eagv su ihnmogset ot sraeon hwti in het ntseqiuo ygal&l)(-tAG; +3
amy  anC noeoesm lehp me nsndutreda why A is cet?rnoirc A20F02 pgae :50 liTpre lhixe of 3 gclnaole a cnhias is medorf mfor plnrcgeoola vai ngehydro nad ifldiedus bd.no Is tish vyre srimali ot thaw A si igAri c.nde?b Dedrecsea rybd-ndeooghn tnairomfo wbteeen lcngaelo uoe.meclls +
umpalumpa  The otalnexpnai gniev yb aawilaabrltse ludco korw fi eht usntqoei oulwd sya yatglA&l-;-G .niamttuo Hwoe,ver het otuqnise ssatet taht ehrte is na lt&-;Gga-Aly umatn.oti +


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submitted by cellgamesgojan(43)
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I i,dufreg -iegXnlYyc- si catcellnyhi nreioseddc a yr“rimap ianmo dcai reuustrtc of a epnori”t esnic teh oennitfdii of a miyarrP turcsture of a tnieopr si “a rneali iachn of oianm da.s”ci fI yuo ssem htwi the Pmriary rrsucttu,e sa ni eth stiuoneq t,mse ouy otncan form the nrSoeyacd trrtuecsu of teh nteir,po hcihw is eiemndrtde yb eht eobniyhndogrg-nd cihhw uroscc enetwbe teh ieppted acokbnbe, ednneeidnpt of eht R sp.roug I opeh hsti adem e.sens

orFm diaiwpiek: oyna“edSrc ruruetsct is yllafmor dfdniee yb eht renaptt of yhedgrno bsnod eetnbew hte minoa yorehdng and cyxarolb oengyx oamst in the eetdipp obkbnace”. sasmeh(pi mei)n

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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 sugy dna i teqou from mtncs1eha:eltgr/ort4/escipots-s.ptes2uece.oiib/lts/owtrwfpewid/ma0oh

9%0" ahev an iinidltfabee eciteng tuntoima CLO A11 nda CLO A12
caesus anmrbalo ocglnale criogs-knlsni iav a yeligcn itnbuioustts in hte lrngooalepc emluelco "

hchwi asnme atth IO sah a neicylg tsnouttusiib adn thrfeoer ist abenlu ot ofrm a scyneadro .uusrttruec

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submitted by hungrybox(1277)
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Deu to eynsc'igl alslm zs,ei it sacerte k"ni"sk in teh inamo acdi q.eeecnus seThe kkisn ear ddenee to rlccyetor orfm teh ocrasndey rctrsuteu.

rOhet wren:ssa

  • kdewe"ean nciontrtiae nbetwee cagleoln nda "gatolopycrne - nacolgel + rytcgeaolpno = aetlgcal.ri heT sioqnuet stme inmtoens namy estdcfe ni NObE (ptey I ol)nlaceg utb on iotnmne of edscfte ni aOlcWrgaelT (eytp II oanc)lgle
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 +1  upvote downvote
submitted by basic_pathology(25)
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GYlX-y- si bekanocb for elaogncl haalp cia.hn 3 clolneag ahalp hsican prlais to romf pielrt hx.eil eGnicly sah no R pruo,g igalnlow fro xbiiietlfly dan otfnroiam of tlriep exh.li oN lcyiegn steenpvr htis uonioucnts lr,snapigi gretnvipen the firtoanom fo nclloaeg coarneysd uet.rtursc

leaclR ttha cleaephl-shai adn ebtse-hsaet rea eaxsplme of caendsyro srtetuu.rsc Tshi can be ohuhgtt fo a ittaafonnsmei of the pahal xhli.e

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 +0  upvote downvote
submitted by an_improved_me(91)
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hteoArN awy to teg at it is iva oniiilntam:e

.A hndeoygr igdobnn dnwtluo ayllre nhagec nisec irnthee anlenai onr elyicng rea paoB .rl Gly &tg; laA sluhtd'no gahenc owh npoielr is miideofd I( emna it C,LODU fi erhet saw a isetrc raennhcid or ighsn,emto but ton a retga rwesaDn ). hntgino ot ecaidtin atht cloalnge gdeardieotn si dlaeret ni nreospse to na AA btsot.tuuiins s,olA ni eht cnoextt of IO ihwh(c si the rnseigpetn at,nloipmc) ew areaydl nokw tath eth olebrpm otd'nes aveh ngniyaht to do with dee,doirgnat meor whti eth cghnea ni sutnEr uctnfoui.c/ret teHnylso ont'd own.k

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submitted by drdoom(1206)
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eeHr’s noe wya to sselraoofit-mpci-ene “sedaeecdr odbnnr-hydoge anfmoir:t”o Im’ tno a gib anf fo isth neil of ,ngirsaeon tub ltycnleicha liaenna sa a dsei opurg sah moer sdrongy*he fro otlpnaite gryenhdo ondgnib nhat geciynl:

ai:anenl H3C—
nlyegc:i —H

So, l,chlnyet”“ica aelnian wldou pemtir mreo de-bnyonrdgoh ai,fnotmro cwhhi gthmi olwla you to eelimtina tath chci.eo

aTht ,aids ti esesm tomsla pmssiibloe to rlue tuo thuo(twi rvye caniltceh egkeonldw or moes veiddrpo nlxpmierteea )atda hatt hte ygilslht grlear nlieaan esod ont piaimr dnhrgyeo igbonnd eebetwn laolnegc loeslcmeu iav trsiec )saiap(lt tnnreer.eefic nI rmsplie ertms, nscei naleani is grer,al oyu uwlod htikn taht it mtus eomwosh efnteirer twih eth rdngeboninydhgo- ahtt cosrcu thiw eth ptyil-edw yilecng.

---
yl*tSicrt ng,askepi ’sit not teh murnbe of odhsyngre but soal het ttnrsghe of the eoipdl hatt aitcistefla nyhdgeor nnobidg: a dhroeygn nuodb ot a rylongst geaveloeitntcre moecleul ikle onfrilue lliw pap“aer” meor oipvteis da,n shu,t n-obyohgddenr oerm yrsonlgt hwti a nbyrea eoygnx dprmaec(o ihwt a endoygrh eetncncdo to oan,cbr fro .lmapex)e

thrFreu in:gdaer

  1. /hqcm//nudrto/pmht/ecthespisud.wud.lphgh:.ilbewuwl.ed
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hungrybox  cApapertie eth fforte tub htis is arf too ognl ot eb lusefu. +30
drachenx  bruxyoghn si a afniegrk terha +
drdoom  cxedn@rha aah,h na,h imgnco abkc ot tish i azliere i was yoblbarp egiekrongev- lol +1
blueberrymuffinbabey  snit' eth nedghoyr indgobn dedepennt no hte deylthoyxard nielpro nad insle?y os atht wonuld't eylalr be hte esusi rhee niesc othse raen't the aas ibneg e?dreatl +
drdoom  byeber@url Aicncgrod ot eAtlrsb’ MCoB e(se nnaTgset ta it),ghr oyyixhendsryl and rreylixnhodypo ructeintbo hneodygr dnbso tath rmfo eeetnbw the nchasi eia(t“ir,”ncnh sa espopdo ot htc-nra;aini eht ,asicnh of usrceo, aer stearape tpydpo;pselei thta ,is srptaeae oglaelcn ;seiotprn nda ertinniaocst ewenetb trpsaeae cahins tsar[eeap lseito]pdyepp is what we clal qrytnea“aru ruru”t;ecst ese teagnTn ebavo). ndA in tish esc,a as uyo piont uto, eth tesm bsidscree a Gg-tylAl;&a utuitintob.ss hatT emess ot mean wto gs:hitn (1) hte erhte eesparat olnclage lodyspeepipt lilw ton kc“ap s][a tyith”lg ot ofmr eht ltiepr eixhl (aeyuqarr=tn tr)csreutu ew lal okwn dan veol and )(2 rionple gisrn wlil afli to lraey eutqi as ,gynslu ipscmngiormo het aheicll onaiomtrconf tath eiesfdn an ahapl anchi ydrsoea=c(n uttr;uercs teh hspase htta form itinwh a isegnl toeplppdy.ei) +
tadki38097  olas uoy 'antc H ndob twhi cobn,ar sit' tno rolap guonhe +
amy  A020F2 P05 e:satt tifomrona of (gnchlliochrwpaeo si hte telirp leixh )trectsruu aiv yndgehor and i.dsuelidf So A si ctironecr bc hetre are on llegcona ceeoulmsl yet n2d( ettusrurc penahps at elonlogarcp l)eelv +
drdoom  amy@ lprtie ehlix is a eaaqrrtyun rreuutcts cin(se tilerp ilxhe is a apesh htat fomsr NWBEETE etasrape or ua“d”lt cogello-anelcolnrg/ap peptd)ei.s ayPirr,m sdaeyrcno nad aretirty ttucresurs ear inospctdrsei fo a niegls leyitdpppoe. cneO uyo veha 2 ro moer dpeeislppyot crnietgaint with aceh treoh .ge(,. Hmeobilong eclu)lmoe ouy aevh tqrauayren rtut.rseuc +

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 ighmt be nhgkrveintoi it tu,b H bndo frointoma fo 'aas smake the dsncyaeor etcsrturu fo hte oipetnr lec(galno in hsit s.e)ac heT lyG ot alA tnousiubtsit does tsluer in sels H ondb a,rfoimont tbu fo vlnuaiiidd asa' not etbewen lnaloegc eeclosmul tha(t mihgt be more rof eaunaytqrr rsuu)crett

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lpp06  I ithnk het eyk si ni het rwsean ranspg,ih hte earwns nnnmieoitg soHb-dn sasy tpsii"rnDuo fo Hdsbo-n etbewen allegonc hohe"etulslguoA mlc ancleglo osde endogur Hbdgnnio- to orsptpu the lepitr xihle, hist si noed iihtwn eth smea lecnolga Lue llniiokmng.ce fneedrift elglncao seomlecul oscurc avi eth isnyle - oiheylysdynxr nkils done ni het MCE +1
kevin  tish is the eon tcmmeon hatt lnylafi dlehep em dedsantunr yhw hatt asw rntcr.cieo nhtka you +


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submitted by j123(16)
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Pmrariy cretrtuus = amino idca redyancq eouseenSc seucurtrt = teuusctrr roedfm hwit a sgneli aonim dcia qeesnceu eabt( elaepdt se,eht lpaah xehi,l yttic)re reTa trtuuresc = mlitpuel yarcoedsn scrtusruet inagercntti htreogte (ptmleiul btea eldtpea seehts astdcek no opt of caeh hroet, er aryt)cuQanetr restcrtuu = pteroni teuutcrsr refdom frmo iolfndg fo all airetryt trtsuuecsr ot ekma ninidgb sitse, ce.t

ceinS eht lanenia saw tpu in eaclp fo the ,nilGyce hte maryirp ueturrcst saw aebunl to ormf an lpaha hlexi icens halpa exihl stretucrsu ende a icutapalrr uqesenec g(yl - -x )y in drero to mfor yrngedho bosnd to kepe teh elixh ltase.b

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 -1  upvote downvote
submitted by unknown001(9)
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wtha si anloelgc ? a ocdsynera nrioept r.seuucrtt

nweh yuo eeovrm ,iencygl het osmt atnbdaun miona diac , omrf teh ourrpecrs uelmeocl lliw you tge a oreprp yncsraeod rtteurusc ? ON

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unknown001  gnireo thsi +
drdoom  acn ouy ealroe?bat st'hwa rnowg tiwh oyur mmot?cen +


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submitted by lilmonkey(63)
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yGl is lo,arp leiAann is naprlono nad idyochro.bph seeisnsM vnocnoenvseaitr ianutm.to Teehs sAA ehav ferteindf elciahmc pestepiror ciwhh aedl to tpreusddi nertoip ignofld oserydan(c turutr.esc) rmiilSa to lGu - Val sntuboiisttu in ekScil ellC iee.saDs

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