Absorbed amino acids are almost all synthesized\(\to\)protein or catabolized\(\to\)energy
Only ~100g exchangeable store of free amino acids
Synthesis: AAs enter cells \(\to\) directed via RNA at ribosome to form proteins. Liver forms plasma proteins (clotting factors, albumin etc), up to 30g/day
When cells are protein-replete, excess amino acids catabolised
Ammonia goes to liver \(\xrightarrow{\text{urea cycle}}\) urea
\(\alpha\)-keto acids can then (a) enter krebs cycle directly, (b) act as substrate for gluconeogenesis in liver, or (c) be converted to acetyl-CoA \(\to\) fatty acid synthesis for energy storage