Final answer:
Amino acids are broken down by removing the amino group through transamination. The remaining carbon skeletons can be converted into glucose, fatty acids, or catabolized for energy, particularly during fasting or starvation. The liver then processes the removed amino groups to form urea, which is excreted in urine.
Step-by-step explanation:
Catabolism of Amino Acids and Conversion to Fatty Acids
The breakdown of amino acids begins with the separation of the amino group from the carbon skeleton, often through a process called transamination. The liver plays a crucial role in amino acid metabolism along with other tissues. Once the amino group is removed, the resulting carbon skeletons can either form new compounds like glucose or fatty acids, or become oxidized in the citric acid cycle.
In the context of fasting or starvation, where glucose levels are low, the body uses these carbon skeletons for energy, resulting in the production of substances like acetoacetate and acetyl-CoA, which can enter the citric acid cycle. During this state, amino acid catabolism can lead to the wastage of essential body proteins and tissues.
Excess amino acids, which are not needed for protein synthesis, are transformed into intermediates by removing the amino group, which is then converted into ammonia and subsequently urea by the liver. This urea is then excreted from the body through urine.