UWorld Step 1 Qbank: Your world of learning. Subscribe now.

NBME 22 Answers

nbme22/Block 3/Question#30
Which of the following is required for the ...
Glutamine🔍

Login to comment/vote.


 +15  upvote downvote
submitted by mcl(453),

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).


Hexoasmine pathway has been implicated in Insulin resistance and diabetic nephropathy! https://www.ncbi.nlm.nih.gov/pubmed/10997685 (Just was curious why NBME asked this!!!)

+/- apurva(15),


 +13  upvote downvote
submitted by seagull(839),

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.

johnthurtjr  I did not +1  
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 +10  
d_holles  i did not +  
yb_26  I also guessed because both words start with "glu"))) +14  
impostersyndromel1000  same as person above me. also bc arginine carbamoyl phosphate and nag are all related through urea cycle. +  
jaxx  Not a clue. This was so random. +  
wolvarien  I did not +  
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?" +5  
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. +2  
djtallahassee  yea, I mature 30k anki cards to see this bs +3  
taediggity  I literally shouted wtf in quiet library at this question. +1  
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 +1  
drschmoctor  Is it biochemistry? Then I do not know it. +2  
snoochi95  hell no brother +  
roro17  I didn’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 +1  
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. +  
amy  +1 no idea! +  



 +5  upvote downvote
submitted by drzed(89),

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.




 +3  upvote downvote
submitted by adong(51),

you need to add an amine (nitrogen) and most biochem processes from sugar --> amine requires glutamine




 +1  upvote downvote
submitted by redvelvet(20),

If you want to take a look for the clinical importance of the hexosamine pathway & products: https://www.sciencedirect.com/topics/neuroscience/hexosamines




 -3  upvote downvote
submitted by meningitis(310),

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.
dr.xx  you mean, pure luck? :) +12  
impostersyndromel1000  lol pretty sound logic here mate +1  
nor16  same here, Glutamine is a NH3 (-amin) donor, so guessing made sense +  



UWorld Step 1 Qbank: Your world of learning. Subscribe now.