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NBME 22 Answers

nbme22/Block 3/Question#30 (reveal difficulty score)
Which of the following is required for the ...
Glutamine ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
tags: biochem

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 +27  upvote downvote
submitted by โˆ—seagull(1933)
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out of curiosity, how may people knew this? (dont be shy to say you did or didnt?)

My poverty education didn't ingrain this in me.

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johnthurtjr  I did not +3
nlkrueger  i did not lol +
ht3  you're definitely not alone lol +
yotsubato  no idea +
yotsubato  And its not in FA, so fuck it IMO +1
niboonsh  i didnt +
imnotarobotbut  Nope +
epr94  did not +
link981  I guessed it because the names sounded similar :D +18
d_holles  i did not +
yb_26  I also guessed because both words start with "glu"))) +30
impostersyndromel1000  same as person above me. also bc arginine carbamoyl phosphate and nag are all related through urea cycle. +1
jaxx  Not a clue. This was so random. +
ls3076  no way +
hyperfukus  no clue +
mkreamy  this made me feel a lot better. also, no fucking clue +1
amirmullick3  My immediate thought after reading this was "why would i know this and how does this make me a better doctor?" +10
mrglass  Generally speaking Glutamine is often used to aminate things. Think brain nitrogen metabolism. You know that F-6-P isn't an amine, and that Glucosamine is, so Glutamine isn't an unrealistic guess. +6
djtallahassee  yea, I mature 30k anki cards to see this bs +6
taediggity  I literally shouted wtf in quiet library at this question. +2
bend_nbme_over  Lol def didn't know it. Looks like I'm not going to be a competent doctor because I don't know the hexosamine pathway lol +25
drschmoctor  Is it biochemistry? Then I do not know it. +5
snoochi95  hell no brother +1
roro17  I didnโ€™t +
bodanese  I did not +
hatethisshit  nope +
jesusisking  I Ctrl+F'd glucosamine in FA and it's not even there lol +
batmane  i definitely guessed, for some reason got it down to arginine and glutamine +3
waterloo  Nope. +
monique  I did not +
issamd1221  didnt +
baja_blast  Narrowed it down to Arginine and Glutamine figuring the Nitrogen would have to come from one of these two but of course I picked the wrong one. Classic. +2
amy  +1 no idea! +
mumenrider4ever  Had no idea what glucosamine was +
feeeeeever  Ahhh yes the classic Glucosamine from fructose 6-phosphate question....Missed this question harder than the Misoprostol missed swing +1
surfacegomd  no clue +
schep  no idea. i could only safely eliminate carbamoyl phosphate because that's urea cycle +
chediakhigashi  nurp +
kidokick  just adding in to say, nope. +
flvent2120  Lol I didn't either. I think this is just critical thinking though. The amine has to come from somewhere. Glutamine/glutamate is known to transfer amines at the least +1
l0ud_minority  No fucking clue I guessed wrong:( +

 +18  upvote downvote
submitted by โˆ—mcl(670)
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The question is referring to the hexosamine pathway.

Carbamoyl phosphate and arginine are involved in the urea cycle. So is n-acetylglutamate (NAG) (regulates production of carbamoyl phosphate).

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Hexoasmine pathway has been implicated in Insulin resistance and diabetic nephropathy! (Just was curious why NBME asked this!!!)

+4/- apurva(101)

 +14  upvote downvote
submitted by โˆ—drzed(332)
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I tried to use logic to answer this question (I did not know about the hexosamine pathway). Here is my attempt--this is probably wrong somewhere.

I figured that if you want to make glucosamine, you need to combine glucose + an amine group

(A) Arginine I knew was involved in donating nitrogen, but it is in the urea cycle, so I figured this was probably not the answer but it had potential. I figured that the major way this compound removes its nitrogen is through urea, though.

(B) ATP. Since F6P already has the phosphate group, I figured ATP is probably not necessary as the compound in question already has a PO4 group.

(C) Carbamoyl phosphate. I knew this was involved in both the urea cycle and nucleoside synthesis, so this was less likely. It also is the product of a NH3 and CO2 so that means that I wouldn't expect it to donate an amine group

(D) Glutamine I figured has an amine group attached to it ready for donation. I also know that transamination reactions are common with amino acids and alpha-ketoacids (e.g. alpha ketoglutarate with alanine can get you glutamate and a pyruvate via ALT) thus it made sense that an amino acid could donate an amine group.

(E) The only thing I knew about NAG was that it was used in the urea cycle as an allosteric activator of CPS, so I didn't think that it was useful as a donator of nitrogen since its function is to help aid nitrogen excretion.

So then I was stuck between A and D, but based on transamination reactions, I picked D.

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makingstrides  Also, L-arginine converts to NO +
madamestep  This was my reasoning too! Fructose to glucose + amine โ†’ Need to add an amine. Glutamine is in a lot of other processes for donating N and becoming Glutamate. +

 +3  upvote downvote
submitted by โˆ—adong(144)
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you need to add an amine (nitrogen) and most biochem processes from sugar --> amine requires glutamine

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 +1  upvote downvote
submitted by โˆ—redvelvet(56)
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If you want to take a look for the clinical importance of the hexosamine pathway & products:

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 -4  upvote downvote
submitted by โˆ—meningitis(643)
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Process of elimination on this one.

  • I eliminated Carbomyl phosphate, Arginine due to urea cycle.
  • I eliminated ATP because ATP alone wouldn't change F6P into glucosamine
  • NAG I got lucky and I eliminated it due to its use in ECM and collagen so I didn't think it was relevant and I kind of remembered it being in urea cycle.
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dr.xx  you mean, pure luck? :) +13
impostersyndromel1000  lol pretty sound logic here mate +3
nor16  same here, Glutamine is a NH3 (-amin) donor, so guessing made sense +

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