[Borek]

Naturally occurring aminoacid A enzymatically decomposes to biologically active compound B. During the reaction side chain of the aminoacid doesn't change. When 31.0 mg (0.2 mmol) of the aminoacid was burnt, products contained 52.8 mg of CO₂ and 16.2 mg H₂O and no traces of sulfur were detected. During analysis the substance B 1 mmol (111 mg) sample produced 33.6 mL of dry nitrogen, 220 mg of CO₂ and 81 mg of H₂O. Identify A and B and explain what is the enzymatic reaction.

[delta609]

L-Histidine (A) decompsoing into Histamine (B).  I believe this reaction explains the inflammatory response we receive in our mucas membranes during allergy season. 

[Sunil Simha]

A is Histidine because it is the  sole amino-acid which contains no sulfur and 6 carbon and 9 hydrogen atoms.
B is C₅H₉N₃. It appears as though the enzymatic process is de-carboxylation of Histidine to form histamine.

[Borek]

Yes, these were both the right answers (although only the second one mentioned it is decarboxylation).

[Big-Daddy]

How did you work out the moles of N2 gas produced by the reaction, given the volume is 33.6 cm3? Don't we need the molar volume or mass?

[Borek]

How did you work out the moles of N2 gas produced by the reaction, given the volume is 33.6 cm3? Don't we need the molar volume or mass?

If no other information is given you should assume STP.

[Big-Daddy]

How did you work out the moles of N2 gas produced by the reaction, given the volume is 33.6 cm3? Don't we need the molar volume or mass?

If no other information is given you should assume STP.

If V_m=24 dm³mol^-1 then I got the answers as above, except with the moles of N in the formula for B being 2.8. I wasn't too sure I could round this up to 3, so I thought I might have made a mistake.

Anyway thanks, good practice for combustion analysis.