When amino acids are oxidized to form cellular energy, their amino groups are removed and liberated as ammonia (NH3).

Here's a breakdown of the process:

1. Deamination: The first step in amino acid catabolism is the removal of the amino group. This process is called deamination.

2. Ammonia Production: Deamination releases ammonia (NH3) as a byproduct.

3. Urea Cycle: Ammonia is toxic to the body, so it must be converted into a less toxic form. This conversion occurs in the liver via the urea cycle, where ammonia is combined with carbon dioxide to form urea (NH2)2CO.

4. Urea Excretion: Urea is then excreted from the body in urine.

While the amino group is the primary group removed and liberated as ammonia, the remaining carbon skeleton of the amino acid is further broken down for energy through various metabolic pathways.