AP BIOLOGY

Detailed explanation-1: -Several amino acid transporters, such as citrin, an aspartate/glutamate carrier protein that supplies aspartate to the urea cycle, are involved in shuttling metabolites into the urea cycle. CPS II, through the pyrimidine synthetic pathway, leads to the formation of orotic acid.

Detailed explanation-2: -Aspartate is the source of the second amine group on urea. Recall that aspartate results from the transamination of oxaloacetate and glutamate via aspartate transaminase, which requires vitamin B. Argininosuccinate is converted into arginine via argininosuccinate lyase.

Detailed explanation-3: -Glutamate is the one amino acid that undergoes oxidative deamination to liberate free ammonia for the synthesis of urea. Once free ammonia is formed in peripheral tissues, it must be transferred to the liver for the conversation to urea. This is carried out by the ‘glucose-alanine cycle”.

Detailed explanation-4: -Five -amino acids are involved directly in the urea cycle (ornithine, citrulline, aspartate, arginosuccinate, and arginine ).