Here's why:
* Amino acids are the building blocks of proteins.
* When proteins are broken down, the amino acids are deaminated, which means the amino group (NH2) is removed.
* This amino group is converted into ammonia (NH3), which is toxic to the body.
* The liver converts ammonia into urea, a less toxic compound.
* Urea is then excreted by the kidneys in urine.
Therefore, urea is the primary nitrogenous waste product of amino acid metabolism.
