Final answer:
The statement is true; amino acids break down in the liver with the nitrogen-containing amino group being removed, which then undergoes a process to form urea, the principal waste product of protein catabolism that is excreted in urine.
Step-by-step explanation:
The statement that amino acids break down in the liver, and the nitrogen-containing amino group is removed, is true. During amino acid catabolism, excess amino acids or those released during periods of stress such as fasting or starvation undergo deamination. In this process, the amino group is separated from the rest of the amino acid molecule. The nitrogen from the amino group is transformed into ammonia, which is further processed into urea through the urea cycle in the liver. Urea is a less toxic form of nitrogenous waste and is excreted from the body in urine.
- The liver plays a crucial role in the metabolism of amino acids, where transamination reactions often occur, allowing nitrogen to be conserved and reused for various metabolic processes. Eventually, the nitrogen is concentrated onto glutamate, which can be efficiently deaminated. This nitrogen conservation and processing are essential because amino acids cannot be stored by the body and their breakdown can lead to toxic byproducts if not correctly managed.