Question

Since ammonia is neurotoxic to urotelic organisms, which includes humans, nitrogen atoms can be transported from tissues to the liver and kidneys as

a) Glutamic acid
b) Glutamine
c) Aspartic acid
d) Alanine
e) All of the above

Answer 1

All the above participate in the ammonia excretion

Step-by-step explanation:

The amino groups present in the amino acids are required to form the urea. The ammonia disposal takes place un the liver by the urea formation and is excreted in the kidneys by urine. When free ammonia is produced in peripheral tissues, it is transported to the liver by glucose -alanine cycle, alanine in transported in the blood to the liver, where is converted into pyruvate.

Another pathway is by glutamine synthase/glutaminase system. The storage and transport of ammonia to the liver is glutamine from glutamate by glutamine synthetase: NH3 + glutamate → glutamine once in the liver glutamine is transformed into glutamate again by glutaminase enzyme: glutamine → NH3 + glutamate.

In the liver takes place the urea cycle, the amino acids transported into the liver can be converted to aspartate. This aspartate enters the urea cycle forming an intermediate of the cycle, and the final product is urea that is excreted by urine.