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).

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.

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

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

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.