Final answer:
Amino acids entering the liver are metabolized through transamination and oxidative deamination, producing urea which is excreted in urine. Excess amino acids can form glucose or fats, or be catabolized for energy through the citric acid cycle.
Step-by-step explanation:
Pathway of an Amino Acid Through the Liver and Excretion from the Body
When an amino acid molecule enters the liver, it may undergo transamination, where the amino group is transferred to an α-keto acid, converting the amino acid into a corresponding α-keto acid and the α-keto acid into a new amino acid. This is followed by oxidative deamination, releasing ammonia, which is then converted into urea through the urea cycle. The carbon skeleton leftover from deamination may form glucose or fats, or enter the citric acid cycle to be used for energy. The urea produced is then excreted from the body through urine, thus removing nitrogen waste. If the body has excess amino acids, these may be converted into glucose or ketone bodies, and if not used, they will be broken down with nitrogen excreted as urea.