AP BIOLOGY

Detailed explanation-1: -The liver produces several chemicals (enzymes) that change ammonia into a form called urea, which the body can remove in the urine.

Detailed explanation-2: -The liver is where urea is created. The urea cycle is a cyclic mechanism that produces urea from ammonia, carbon dioxide, and aspartate.

Detailed explanation-3: -In humans and mammals, almost 80% of the nitrogen excreted is in the form of urea, which is produced through a series of reactions occurring in the cytosol and mitochondrial matrix of liver cells. These reactions are collectively called the urea cycle or the Krebs-Henseleit cycle.

Detailed explanation-4: -The liver prepares urea by combining two molecules of ammonia with one molecule of carbon dioxide in the urea cycle. Urea actively plays an important role in the countercurrent system of nephrons which allows the re-absorption of water molecules and other unwanted ions from the urine being excreted.