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NBME 23 Answers

nbme23/Block 2/Question#4 (58.1 difficulty score)
An 18-year-old woman comes to the physician ...
Maximum oxygen consumption (VO2max): decreased;
Venous blood lactate: increased;
Energy production by glycolysis: increased
๐Ÿ”

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 +7 
submitted by joker4eva76(25),
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The eutsnioq mset is ibirncsedg a rmaodiohlicnt aidssee, hhcwi yonmlomc rspntee whit ailctc aodicis.s Treeh si an iesnecar in orcaiaben smfro fo yegern irtupndooc ysllc.i)gos(y heT aihnmcrodiot are f,ayutl so ehty cโ€™ant ues teh ned tudrcpo of lgisclysyo pt(ruav)ey in .CTA eItdsan etrupavy is sutdhen voer nad is duse yb HLD (actlate )earghndsyedeo ot rneteage rtpyeuva.

:dAeis celRal atth DHL esus HNAD nad atgersnee .A+ND iyenicDcfe of LHD anc aedl ot loss fo onreengiatre of D+AN dna nihtisbi olsyc.lyigs

drdoom  ... pyruvate is shunted over and is used by LDH (lactate dehydrogenase) to generate lactate*. +3  
chris07  It's hinted in the answer, but I would like to clarify: max O2 consumption is decreased because O2 is consumed in the Electron Transport Chain, which occurs in the mitochondria. With the mitochondria not working, the ETC cannot work, and thus there is less demand for Oxygen. +17  
masonkingcobra  Mitochondria are the powerhouse of the cell +50  
uslme123  Apparently ragged red fibers are the result of coarse subsarcolemmal or intermyofibrillar mitochondrial accumulations.. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/mitochondrial-myopathy +2  
mnemonicsfordayz  As @chris07 said, less O2 is being consumed in the ETC... but I also was thinking that the diaphragm is a muscle and if the mitochondria in her diaphragm are also not functioning, then she's not breathing properly and less O2 is being inhaled and therefore decreasing her oxygen consumption. Is that totally off base or am I just grasping at straws here? +  



 +4 
submitted by nwinkelmann(285),
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So sthi eosiqnut wsa teimogshn I leryal sdglegutr i.hwt I dtnd'i igzcereno ttha teh iatrnsnteeop saw of RMREF sa mnoeeso dsatte el,owb dan I onwk uyo tdon' deen ot wnok tath ot anersw hte uqtio,sne tbu ti dlouw vaeh bene epl.fulh yM teggbis raiftunosrt swa teh ginrwdo fo teh obpyis srteusl bnaa"omrl atisalcuumnco of .t"haooimdirnc Tish yeadnon me acbusee het eiitnodnif fo ragegd der iefsbr hh(icw 'Im musagnsi aws riteh oitnnien)t si ntcaumcsliu"oa of baaolmnr ai"htnm.ioodcr Thsoe are tow vyre deiftrfen tsattensme in my ind,m lol. ehT sitr,f ot e,m jsut emasn re'sthe oot cmhu rhdcntaoio,mi tbu het osnecd snmae reteh's oto mcuh NDA hety arent' tncioingunf .yplropre sI't osal stju eht catf fo iebgenmrmer lla fo eth etmsr orf TCE ta teh meit of nrgdeai the quitnoes e.i(. I i'nddt ntkih obatu hte tafc htta CTE si sola daecll lrleulca oresrnapti ro tujs tar)rsopnii.e

I laso 'nddti aylelr edusrndnat lufyl ahtw 2OVmax is = V"O2 ,xam sola wnkon as aimxmla geyxno utke,pa si the manmseterue fo the miuamxm toamnu of egyoxn a eponrs acn iletzui irndug itnsene rx..seei.ce and si bsaed no eht erisepm that teh rmeo exgony mnoedsuc rdnuig rcee,sxie eth rome hte oydb lilw eenergat nsendoaie ptpheoitsrha TPA() egyren ni lsl...ce O2V mxa is radeehc nhwe yuor ognyex cmsuiopnnto irnsmae at a asedyt ettas psetied na nreceasi ni het r.wlokado tI is ta htis eputala ttah hte s[mcul]e ovsem orfm aoiecrb otebamsmil ot naerocbia oabe"sltmim pleielh9wsow--rh-i2o/fw.sw/v0t/mamt13x:-20.cyt7avtw.

Bdase eurply no sith oind,teifin ewhre Omxa2V = lltsenisaey hte tmie ta wchhi ecbiaor thswecsi ot cbnroaeia prin,iortsea my nttertropaniie of too cumh raoihdtcoinm vs too cmuh dan dba diairothcomrn di'tnd emtt,ra seuebca enve nhew het nmhoiaidtcro era itgncfunino pe,yplorr etyh aherc a itnop dan hsiwtc to reaoncia,b huts fi ereth wsa too chmu mnloar tcidoa,nrhmio htis luwdo cuorc asrtfe seacbue rteeh doulw eb mreo vlerlao uacrllel sorientairp gncoiurc, iemnang eth dybo wludo htwics to earicanbo adn zuiilet ilsigcsoyl to tcltaae orf ,erneyg psto niigliztu eht ani,odohicrmt nad hust 2OxaVm ouwld as.eerecd

EWRV...EH.O ecasbeu hist si a MRFER e,ntsqiou eht derro fo vseent si a tillte fn,dfeeitr dsepiet hte omuotce ienbg the same (at satel shtta' how I asnterudnd .)ti So, I tkinh eht eky ot yan indaorctlhmoi srdeoidr is brrmegeenmi ahtt the otitnmsau aer mlsoat tiarnlecy giogn ot afcfet na nddeeco nioretp dan thsu a fiyecdecin of htat p.eirton enO latcier atth I unodf sida that hte NARt utsinmato s(a ni EMF)RR e:acus tpsi"urd aooiilrmtcndh ioentpr nsihtseys, riesgcdnae eht iaivctyt of xCpeoml I dan ot a esrles netext eomCplx I.V.. hicwh casedrese tsriapeniro nad srolwe otnorp impunp,g iaatladrycml dsaeigcnre hte bnemrmea aotplntie nda oportn teocceaihrclmle onptiaetl irdegtan corass eht cminrltdioaho niner ebne.mmar heT rnopot lchermelotcieca taitpenlo tidgrean is teh irvngdi cofre rfo ATP sstesyhin dan rcdeaigens it stayulbtsilan wrlseo hte lxmaima trea fo PAT h.s"itnesys lyr0..l./o4p.u/t1n.r09t./clm/o0x0e3n1dlwii/439e-:l9bof6fj.hs0i6b7/e1i2ays.6112

dBeas on ym tndnseradgiun of avtdexoii hpolhi,ptnooasry O2 notcnmuispo (..ie nikgta teh reectlon form emlcxop VI and tupignt it no 1/2 2O to ectear O2H dna H+ riveds teh roontp tdeanirg cihhw edrsvi APT tpnurdo.ioc sh:uT cendfeiit irrsoeytrap iodixonta i.(e. DmNtA tiaomunts fo the CTE z)enyems aesld to deloewr 2O tnpoumsiocn (so welreod 2VO )mxa chihw tenh eslad to wdleore TAP cniuo,rdpto adn tush evifdetec a.otdorinimch hneT, eldroew lniahooitcrdm uonifntc asedl to dcresedae rbcaoie iiaornpetrs ngsnuhti APT odrpicunto ot ciaaborne raenotrspii, vdrnei yb sygco,liysl dna tsuh aeignrsinc attceal .slleve

opeH isth leh!sp sThi otok em WYA OTO LGNO to uirfge uot, llo, tbu lelfhuyop I evner kanigrfe tfroge i,t .lol

l,Aos fi uoy wnta any reom ridegan, I anlifly funod na eairlct thta llayautc ulfyl elnsiapx the bclmihacoie nda tioyhooghpapsly of iicrhnmdaoolt eihomy:sapt b1c/paa27c.3c/ctipl/ma/4idmi243nsa:/e61r/3t//rh.te2o5uo

yrroS st'i os g!lon

djtallahassee  lol yea. I thought they were trying to say there was an abnormally large amount of mitochondria present which made me get the opposite answer :/ +1  
alexxxx30  no I so agree. The grammar was completely wrong (clearly whoever wrote the question needs to work on english). This was very frustrating to me because I recognized that it was ragged red fibers, but then the wording made me doubt my own knowledge (thinking how could the test writer mess that up?). abnormal accumulations either means too much or too little. accumulations of abnormal mito means thee mitochondria is faulty. Correct grammar is putting the adjective right next to the word it is describing. So this was definitely wrong and I share your sentiment. This really frustrated me! +1  
azibird  Definitely a mitochondrial myopathy, but I actually don't think it's Myoclonic epilepsy with ragged-red fibers (MERRF). This normally entails Myoclonic jerks, Generalized seizures, Cerebellar ataxia, and Dementia (according to Amboss). Maybe it's CPEO (chronic progressive external ophthalmoplegia): progressive extraocular ophthalmoplegia with bilateral ptosis. Not sure which one would account for her poor exercise tolerance. Either way, recognizing it's mitochondrial is enough. +  



 +3 
submitted by soph(55),
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pt whit gessrvpieor eumcsl -ksnesg&;awet- sper lceumss nto wingkor -;>- eecsreda gynoex tonmsp.iuocn on oe=xgyn no brceaio ebiolmatsm &t;--g irsaenec noesuv ,actetla soal uoy eepk nogdi oarecniab gcyilsoysl necsi uoy acnt og ot ACT t--&;g sncierea yeegnr noocdiuprt iav slioglsyyc ):




 +1 
submitted by diabetes(25),
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nca ymboesod ixalepn owh nyeger riconudpot yb ylicossgly ,ncesaedri nices raciobe icllsyygso updcero 32 net P,mceAoTarp ot 2 etn PAT hrthoug eoriacabn cysyogslil ?

diabetes  i think the stem should be "energy production by an anaerobic glycolysis " +3  
blueberrymuffinbabey  yeah that's the bit that tripped me up too. i get that there would be increased glycolysis in general to compensate for lack of TCA function but...the fact that it says "energy production by glycolysis" is kind of misleading/confusing. +  
thotcandy  technically, glycolysis is the reaction that happens in the cytosol that generates pyruvate and 2 net ATP. after that it's TCA and Oxidative phosphorylation, which occur in the mitochondria. By definition, glycolysis is anaerobic - which is why they hammer the fact that RBC undergo glycolysis only into our heads. +1  
thotcandy  technically, glycolysis is the reaction that happens in the cytosol that generates pyruvate and 2 net ATP. after that it's TCA and Oxidative phosphorylation, which occur in the mitochondria. By definition, glycolysis is anaerobic - which is why they hammer the fact that RBC undergo glycolysis only into our heads. +  
targetmle  i got it wrong because of this as i thought ATP will be decreased in anaerbic glycolysis, but proabably it was mainly 'glycolysis' is increased +1