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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 nkith it hsa gihsmntoe to od wiht ynicelg (ued ot tsi slmla ezsi ti acn fit in mnay esclpa rwehe ohetr aimno scdia nac ton and hncee it ovsredip “rrcluuatst scmeaons”cpt ot hte ngl,eclao ie.. tup a inkk in the laaph l.ehix) If cenligy is idmcelsap yb oseminght ,sele I ’odnt nhtik eoapnrg-ollc can ofmr sit rocrtce ardcnoyse ucturrset.

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jotajota94  ur!Te osl,a eyinclg is 3/1 of oaglnlce afla chsina, so it skmea snese atth tsbuiottnsiu ithw lanniae hc(ihw is chmu )ebrgig duowl aeld to opriustdni ni het alpah ehlxi ifanto.rom +2
jotajota94  Te!ru s,loa cleiygn is 3/1 of oellancg alaf inh,csa so ti ksaem esnes taht isibunottuts whti eannail c(iwhh is cumh eg)rigb wludo aeld ot diunpiotsr in hte aphla hilxe .fraonoitm +
thepacksurvives  nicGeyl si llsma nad ndbey, iwhch lawlos ti to fmro the rilisfb rfo eht pliert exilh +
brasel  loAs in eergaln FA( 2810 gp 0)5 OI si mfor blspmoer ifnormg eht pietrl exilh ihcwh is rseydoanc tsuurrt.ec ,oulrateyFtn yteh gave us oengmsith ot sronae ihwt ni hte etiqnuos ;gtG&-lAlya)( +3
amy  anC eeoosnm pelh me esartnudnd wyh A is cirrtec?on 2F00A2 aegp 0:5 leiTrp lxihe fo 3 elocanlg a nchias is edmorf rfom nclroelapog iva oyndgher dna iedldusif n.obd Is htis ervy imlasri ot awht A is igAnbc. di?re edDsacree hnobe-dngrody tmfaoonir eebwten nagleolc ouelcmle.s +
umpalumpa  hTe tlpeaoannix evnig yb lilarabeawsta ouldc kwro fi teh usenqiot owuld sya G-;A-g&yllat nutio.tam voeeH,wr teh qeisntuo tsetas hatt ehter is na tg;&A-G-yall imtont.au +


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 +13  upvote downvote
submitted by cellgamesgojan(43)
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I iudfg,re g-Xce-nYily si lcahcyliten cenoedisdr a ryapim“r oniam cadi rurecustt of a tnp”eior seinc het fitneniido fo a iaymPrr truercsut fo a nriotep si “a eialnr cianh of oainm a”si.dc fI ouy msse thiw the rmrPiay stertru,uc sa in teh tiqnosue tsme, uoy ctnoan from eth oSayncrde esrtctuur fo the ptiero,n which is nedrdetiem by the d-genrdnbyohinog hwihc uscocr eentbwe eth eiepdpt bcknobea, dntdpieeenn fo teh R urso.gp I phoe siht dema sne.es

moFr wiakpdiei: ndea“Syroc ruutrstec si ollyrmaf dfenedi by eth ttrapen of oehdryng bndos betwene teh nmoai ndgyrhoe nda bcryaolx nygoex mstoa ni the pidepte noeckbba.” iapsemsh( min)e

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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 gysu dna i qetou fmor h.mrwtrtfbeowttapcrio-/hi/useelsp0/snoitt:cpmi.ewloc4/gedsaot1s2ese/

%9"0 ehva na eliedfaibtin citeneg maounitt C OL 11A dna OLC 21A
ascs eu lraabmno aelgclon lgknii-ncrsso aiv a cegnlyi ntssttibiuuo in het prcganoelol muollcee "

chwih mnesa taht OI ahs a eilycgn inbisttouuts dna feterroh ist laebun to rfmo a saeconrdy ts.ureurtcu

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submitted by hungrybox(1277)
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ueD ot n'lceisgy almsl ,esiz ti secetra nis""kk in het maoni adic unq.eeesc sheeT niksk are nedeed ot rrctcyoel rfom het oseacdnyr cst.uuetrr

trheO nwarse:s

  • wdeneke"a otetnaincri beenewt naclolge dan yegartco"nlpo - gnlloaec + notcoeryalgp = ec.llaartgi The qsoeitun mset sotnnmei ynma sdctfee ni NObE t(ype I clnloeag) tub on mntenoi fo dftcees ni OcaaelgrlTW (type II ego)calln
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 +1  upvote downvote
submitted by basic_pathology(25)
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yXY-Gl- si aonkbecb for onlacegl alhpa nc.hai 3 lgnlcoae aplah cnisah parlis to fmro ltrpei eli.hx leynGci ahs on R gup,or olwagnil rof libxiiytfle dan iarmonfot of lrietp xleih. oN icynegl etesnvrp siht isucuonont nis,parlgi entevgpnir eth oinrmotfa of glnacloe nyesdaocr sr.trtuecu

Ralelc hatt hslepailceah- nad thb-aeestse rae plexmsea fo cesnrdayo r.sesuuttrc ihsT cna be htogtuh fo a tmftinoisanae fo het hplaa hielx.

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 +0  upvote downvote
submitted by an_improved_me(91)
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hNtAore ywa to egt ta it is via nemi:naiilot

.A oneghdyr gnoibdn lunotdw rllaye hacgne ecnis threeni aenlian rno yencigl rae rpoB.al lyG tg&; lAa 'nuslhtdo ecngha owh lniproe is mfodieid I( mean it UC,ODL if trhee wsa a tcreis irdhenanc ro hgeomsi,tn tub nto a getra a)n s.weDr nihtogn ot niitadec htat nogelcla tnroaideegd si teerlda in seonrspe to na AA titi.ostbnusu lo,sA ni hte exntotc fo IO hhcw(i si teh esipntnegr l,tai)opcnm ew ayarled nkow atth eth elprmbo tsn'eod evah yingathn ot od whti tedeodgnir,a erom wthi hte hanecg ni u roEstur/ti.cntneufc syotelHn 'dont .konw

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submitted by drdoom(1206)
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’eersH one ayw to mp-toiaesfnro-cilsee ededsrac“e ygoob-edrhndn aotnmifr:o” mI’ tno a bgi fna of sthi einl fo aonesign,r tbu nylahlticce nilanae sa a sdie ogurp sah omer *grhosyden fro ttoinaepl ngohdrey gndnoib than gnliyce:

na:aniel 3HC—
:negliyc —H

,oS tc,hlcyi”n“lae elanian oduwl repimt omre ooybhdenndgr- t,rmniaoof iwhch gihtm lowla yuo to inlmeaiet ahtt hei.cco

htaT aisd, it seesm tsaoml emssilpibo to rleu uot otuwthi( evry hateicnlc dnglowkee ro moes doeidvpr eeipxlntrmea )aadt that hte tshliygl rgaler anilnea esdo nto aripim renoyhdg nnodgib wbeeent clnogael cluleomes iva reitsc i(laap)ts nicrnte.efere nI spilrem em,trs einsc aneilna is aleg,rr you wdoul ihntk that it ustm hoewmos nriterfee iwht hte dngb-nrodegihony ttha soccur ihtw teh tdelyi-pw egycnil.

---
rt*lyScti einkagsp, ’ist ont the merbun fo ygsdohnre btu slao het ntrhstge fo teh dleipo that aetitlaifsc eghdrnoy ingdn:bo a edgohynr nbudo to a yrogtsnl ttocganvrleeeie mucollee iekl infureol ilwl a”p“raep eorm tpvsoeii ,and s,htu onh-onygeddbr erom nyrsoltg iwth a yreban yenoxg oaeprc(md wtih a nryheodg ncoendcet ot rnobc,a orf .eplema)x

rhFutre :denagri

  1. hwrnpdqmc.mi/psthupl.u/lgutotc/ed/ud.wedhhseh.l:be/wi
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hungrybox  itecpAarpe eht fofert tub shit is fra oot ognl ot be su.eufl +30
drachenx  hrguoyxbn is a rengfika hrtae +
drdoom  ndcxaerh@ ahha, ,han icgnmo kabc ot thsi i ialerez i saw rplbaybo ge-eeigrovkn oll +1
blueberrymuffinbabey  ins't teh gnoydreh nindgob dndeepnet no the dylxadhtroey ponrlie nda elsyin? so atht toluw'nd laeylr be teh usies ereh nicse setho ta'ner the asa ibeng tare?edl +
drdoom  errbyb@uel nodcigrAc ot l’btreAs CoBM (ees ngstanTe at i,t)rgh sheoylidrxnyy dna orxyhnypelrido nutiotrceb ndorhyeg sbond atth mrof wbteeen the hncsai inrit”(h,anec“ sa spdepoo to h-cairatn;ni the acn,his of se,ourc aer eearstpa ylepipd;opets that si, rtaapese eogcllan et;rnspio and iaeinocnsttr eeetbnw rpaeeast ahcisn aapre[est oypildtse]pep is htwa ew allc aa“terqruyn cttseurur;” see Tnatneg baove). dnA in siht aec,s as you ipotn ot,u hte etms edrsebcsi a &t-AGl;lgay busuo.ntstiit atTh ssmee ot nmea owt :stnghi 1() eth three trpeaaes lcnalgoe oepltyepdpis liwl tno pac“k ]a[s ihglt”ty ot omfr the ilerpt hixel q=yrtauren(a rettr)uscu we lal nkwo nda eolv nda 2() inlroep rsngi ilwl lfai to yrale etiqu sa gynu,sl nropcomismgi teh cehalli toacoonmfnri htta esnedfi an hpala hinac cydroa=ne(s scttur;ure teh paehss tath rfmo iwtihn a esglin pl).tpopeidey +
tadki38097  soal uyo cn'ta H odbn tihw ncabo,r sti' ton roapl gnouhe +
amy  2A00F2 05P t:aest oofntarmi fo larhelcwcgohipo(n si eth tepirl eihlx uert)urcst aiv eyogndhr and sif.dedliu oS A is nertrccio bc ether rea no nleoclga oesmelulc tye n(2d trcurseut nhpapse at pcorgllaone elevl) +
drdoom  y@am treipl lixhe si a aeqratnruy eurustrct sneci( ptleir eixlh is a epsha thta omrfs ENEWETB sepaeatr or tu“”adl ergepcl/lnolocolaagn- d.ti)sppee rPimar,y asndeoyrc nad rryteiat rursetcstu rae iircnsstepod of a eilsgn ppiteopely.d Oecn yuo evha 2 ro roem ilpyoeedpspt neitagitnrc twih echa rhtoe .,(ge. ongieHboml coeulelm) uyo heva utarernyaq erttcu.rsu +

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_

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submitted by nmb29(0)
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I ghtim eb iikonhrtevng it t,ub H bond oiftamnro fo 'asa aesmk hte andeosycr errcsuttu fo hte eprtnio naolcl(ge ni shti a)sce. The yGl ot alA utsotuitnisb osed luestr in lses H dbno ,rfainmtoo btu of udlidnaiiv as'a nto enweetb ogelcanl eselolcmu tt(ha ihtgm eb roem rfo rqeunayart srrutte)cu

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lpp06  I nitkh hte yke is ni hte rawnes pasinr,gh eht eswrna itgomnnnie -Hodbns asys sutpoiDrni" of bn-Hsod eewtben locgaeln l"eulscuhmhAotogle llgnoeac dsoe reugnod nnHiog-db to tursopp eht teplir xheil, tshi is eodn hnitwi het msea llgaocne ciougk. leenlmnLi infrteedf noeglcal luemlsceo orscuc avi teh syeiln - sdhxryeiynoyl ilsnk enod in teh MCE +1
kevin  siht si hte noe omcmnte taht llyaifn lehpde me tsnadrndue yhw ttha aws roeri.ncct hnakt uoy +


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submitted by j123(16)
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mryiPra uttcsrreu = manoi dcia ysuee crqnaSoenedc euctsutrr = tucruerts rmeofd wtih a sgelni iaonm dcia uscqeene t(eba apleetd hts,ee alaph lh,eix crireaeTtt)y cretsrutu = tlmilepu sayerndoc urtutscers tenincirtga thoegert lt(elumip ebta ldeatpe tehess cakedts no pot of hace ,hotre nayQer rae)rtuct uruttcres = rteipon rcusutetr mdoerf fmro dfgionl of lla ertatryi tucertrsus to ekam nbigdni ,tsies .tce

Senci hte ilenaan swa utp ni lcpae fo eht Gcyin,le hte priamyr ertruucts wsa ublean to ormf an lahpa xlhei siecn hlapa ehixl ctrrstuseu dnee a upiactarlr queences y(lg - x- y) ni reodr to form ngeodhyr bonds to eepk hte hiexl tsbl.ea

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 -1  upvote downvote
submitted by unknown001(9)
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wath si lclegano ? a aedconsry ptrneoi cutt.rersu

wnhe uoy emervo g,ycneil het mots atdnaubn monia acid , form eht rrcupoers elecomul lwli oyu tge a eprrpo osycderan uucstertr ? ON

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unknown001  negoir hits +
drdoom  cna uyo rtbleaeo?a w'tsha wgnro with yrou ec?mnotm +


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submitted by lilmonkey(63)
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Gly si arlp,o enalAin si alporonn dan hcoybrihp.od snsMiese nvnoiscrveteoan nua.itotm hseTe AAs aveh eirntefdf mhicleac etprpisero cihwh adel to ripddsuet riptone ifgnldo asoyncred( su)trtru.ce riliaSm ot lGu - alV bounstutisit ni kSelci llCe ese.iaDs

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