QuestionSBA
QuestionChoice
Nitric oxide is a signalling molecule with a single nitrogen atom. It is not used as a source of nitrogen for urea synthesis.
10024012
c
Nitric oxide (NO)
QuestionChoice
Urea synthesis involves the combination of ammonia (NH3) and carbon dioxide (CO2) in a series of enzymatic reactions. Two ammonia molecules contribute their nitrogen atoms to form the two nitrogen atoms found in the urea molecule. This process occurs in the liver and is a key part of the urea cycle, which helps eliminate excess nitrogen (ammonia) from the body. Aspartate also contributes to the requirement for nitrogen atoms.
10024010
a
Ammonia (NH3)
QuestionChoice
Whilst nitrate contains nitrogen, it is not directly used in the synthesis of urea. Nitrate can be converted into nitrite and then into ammonia, which can then be incorporated into the urea cycle.
10024011
b
Nitrate (NO3-)
QuestionChoice
Nitrogen gas (N2) is abundant in the atmosphere but is not a form of nitrogen that the human body can readily use for urea synthesis. It needs to be converted into ammonia before it can be incorporated into the urea cycle.
10024013
d
Nitrogen gas (N2)
QuestionChoice
Uric acid contains nitrogen, but it is not directly involved in the synthesis of urea. Uric acid is the end product of purine metabolism, and excess nitrogen in the form of uric acid is excreted in the urine. It is not a precursor for urea formation.
10024014
e
Uric acid
Concept
Chapter
2693
5717
Urea Cycle
Topic
281
Muscles
17200
The formation of urea requires 2 atoms of nitrogen.

Which of the following is a molecule they come from?
a