Terrestrial vertebrates use the urea cycle to convert the ammonium ion to urea such that the urea can be excreted. In the production of urea, only one of the nitrogens in the product comes from ammonium ions. What is the source of the other nitrogen?

Asparate is the source of other nitrogen

Explanation:

In the terrestrial vertebrate urea cycle is present which converts ammonium ions to urea and then this urea is excreted out of the by through urine.

First ammonia and bicarbonate combine to form Carbamoyl phosphate. The Carbamoyl phosphate and ornithine get condense to citrulline. Until here the reaction occurs in mitochondria.

Then the citrulline is transported in the cytosol where another nitrogen is added by an amino acid called aspartate and citrulline is condensed into argininosuccinate and aspartate converts and released as fumarate. So the correct answer is aspartate.

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.