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NBME 21 Answers

nbme21/Block 1/Question#17 (82.4 difficulty score)
A 7-year-old girl is brought to a clinic in a ...
Methionine๐Ÿ”,๐Ÿ“บ
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 +25 
submitted by usmleuser007(397),
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If yuo dntolu'c rebermme hwchi rewe nt;ieealss neht eantatlivre wdulo ehav neeb ot erelzia hatt ignrwgo dcerhnil eend llcse ot ivedid. siTh qsuirree NDA eitipnoarcl nad rntasoa.tlin Of ihchw teh eunlcic daic hmiyte is ip.trtmaon It erruqsie a mehlty stnarref.

ihTs is rhwee onnheiimte eocms n.i Menotenhii cbmisneo wthi TAP to rfmo MAS a( hmeylt rndoo)

whossayin  Thatโ€™s a legendary explanation. Thanks dude! +  
makinallkindzofgainz  This is exactly how I solved it! I remembered that Methionine is essential for methyl transfers, and you would need that in dividing (growing) cells. But now I'll just remember PVT TIM HaLL too :) +2  



 +15 
submitted by nosancuck(87),
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oY gadw ew lla tboua VTP MIT aLLH

enanPl,hlnayie alenVi, ryNKDtApT,o ,rneoThein csIeeonu,li nite,Monhei Hdti,nisie eiLncue nsieyL

meningitis  I don't understand what the question is asking... can someone please explain it to me? Patient doesnt eat protein, shes chubby. What does methionine have to do with this? +2  
charcot_bouchard  Just basically asking which is essential amino acids. +3  
usmleuser007  Essential amino acids (something i came up with) 1. "Three HAL fans will try meth" a. Threonine = Three b. Histidine; Arginine; Lysine = HAL c. Phenylalanine = fans d. Valine; Isoleucine; Leucine = will e. Tryptophan = try f. Methionine = meth +3  
nala_ula  They're saying there is a lack of good quality protein -> slight nutritional deficiency. She may have acquired weight but it's not because of protein. So they're specifically asking what amino acid she might be missing due to her subpar diet. Since essential amino acids are those that the body cannot make itself, out off those listed, methionine is the essential amino acid. It's on page 81 of FA 2019. +11  
nala_ula  correct me if I'm wrong please :) +  
hello  For anyone confused trying to follow @usmleuser007's comment -- slightly modified Essential amino acids mnemonic "Ah, Three fans will try meth" Ah = arginine, histidine Three = Threonine Fans (phans)= Phenylalanine Vil (Will -- German accent pronouncing English word 'will') = valine, isoleucine, leucine, lysine Try = tryptophan Meth = Methionine +1  
pg32  Why does @hello and @usmleuser007 mnemonic contain arginine? That isn't in the PVT TIM HaLL mnemonic for essential amino acids... +  
paperbackwriter  @pg32 arginine is semi-essential. It is essential in preterm infants who cannot synthesize it https://www.sciencedirect.com/science/article/pii/S0955286304000701?via%3Dihub +  



 +8 
submitted by usmleuser007(397),
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.1 re"The HAL snfa wlli tyr t
eh"m    .a ihroTenne = heeTr 
    b. tens;iiHdi nAni;iegr yneLsi = 
LHA    c. Pnennaelahyli = 
nfas    .d leV;ain inoIlue;sce Lneucie = lwli
    e. yoTrptpnah = t
ry    f. henonietiM = 
tmhe
pparalpha  Thanks! Good mnemonic +1  
b1ackcoffee  best mnemonic +  



 +5 
submitted by usmleuser007(397),
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saestnlie niomA icads AA)(

)1 usdAtl eriureq 9 A(A) = labe to keam rnignae vai raeu ec)lc2y eCdhlinr iurreeq 01 AA() = htye era tisll dn iepeovg3l) Wthi PUK irsnteoy obscmee ltneeisas ni bhot daults nad hrncelid




 +3 
submitted by drzed(220),

Let's say you didn't know methionine was essential.

(A) Alanine -- you can create alanine from the enzyme ALT (alanine aminotransferase), thus this enzyme cannot be essential

(B) Aspartate -- you can create aspartate from the enzyme AST (aspartate aminotransferase), thus this enzyme cannot be essential

(C) Glycine -- this one is low yield, but it is made from serine (serine + THF -> CO2 + Me-THF + glycine). If you didn't know about this, you had a 50/50 shot

(E) Tyrosine -- you can create tyrosine from phenylalanine (unless of course you have phenylketonuria), and thus this cannot be essential.




 +0 
submitted by hello(315),
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For aoneyn nsodufce nrgyti ot loowlf @sle7eu0'smr0su mocntme

lylthgiS omediifd

aesnltsEi nomia asdci imnncmoe A,"h eThre nfas iwll ytr hemhett"

Ah = rgiain,ne nieidtshi

heTer = nhrTnioee

Fsan (hps)=na yePneaninlalh

lliV lwl(i -- marnGe tacnec inuocnporgn gElsihn rodw "l"l)wi = ln,ivae ol,nceeusii in,eelcu yilesn

yrT = tpaprhntyo

htMe = nhoiMeteni




 +0 
submitted by mrglass(38),
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ehT ywa I meerbemr het ntseailse monai asdci is yb reinfgeenrc hte namoi sdcia opursg I eaadlry wko.n oS het stiesanle niaom dscai rae:

  1. eTh cdrhenab anhic onmai sdci:a Iiluocsene, e,cnLiue nda lainVe

  2. heT nigerd miano dcisa XTPCEE iyresoTn wchhi( moscebe stesleian in otseh ithw P)KU: Tpaoyptnhr, idiniHste, lyennlPiheana

  3. hTe ulfurs ignnicaont miaon ica:sd tisnyeCe nda seniHdtii Yu(o lliw ees bteaed vore hteerhw estenyiC efquisali sa saenielts or t)on

  4. Teh tow uoy sjut ahev ot iozmemr:e neTreinho adn yiensL

mrglass  I meant to say Cysteine and Methionine* +  



 +0 
submitted by saqeer(3),

a little misleading her increase in weight made it seem as if she had low thyroid hormone and tyrosine is a precursor.

b1ackcoffee  but hypothyroidism would decrease the height. +  



 -3 
submitted by codyluvr95(6),
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B12 csmeo rmfo piretno dna is a ssneaeyrc fccaoort ofr oteeinhnim shnt.esya owL 2B1 = olw miitnone.he




 -3 
submitted by mcl(599),
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neiehioMtn is na etaenslis imnao ic.da llA estohr ledtis aer tno.

scalpelofthenorth  Pg 81 Tyrosine is listed as an essential AA. Should be tryptophan for those who got this wrong like me. +  
neonem  But tyrosine can come from phenylalanine, so it's not really essential right? +1  
gh889  in FA2019, it is listed as Tryptophan, not Tyrosine. That was corrected. +16  
usmleuser007  Note: Tyrosine is ONLY essential with PKU in children +  
niboonsh  bro FA2018 lists tyrosine as an essential AA. They played us. +1