Amino Acids

Functions
Amino acids have interconnections with other biochemical processes of the body. They can be used for energy (ketogenic), or be converted to glucose (glucogenic). Ketogenic amino acids can convert directly to acetyl CoA, while glucogenic amico acids can convert to intermediate molecules in the Krebs cycle, which can contribute to the synthesis of glucose.

Amino acids also contribute to the formation of nucleic acids, spingolipids, hormones, peptides, and other molecules.

Mnemonics
Essential 10
"Private Tim Hall" (Phe Val Thr Trp Ile Met His Arg Leu Lys).

Purely ketogenic
Only leucine and lysine are not glucogenic.

Both glucogenic and ketogenic
"Tip" ([Thr Tyr Trp] Ile Phe).

The remaining amino acids are purely glucogenic.

Excretion
Excess amino acids are not stored, so they are used as energy or converted into other molecules. In this conversion, the -NH₂ groups are removed (by transamination), transported, and excreted as urea:

1. By transamination, 2-ketoglutarate transfers its oxygen to the amino acid while removing and taking on the -NH₂ group to form glutamate. (2-ketoglutarate is a Kreb's cycle intermediate, and a nitrogen transporter).
2. Glutamate travels to the liver and releases ammonia (oxidative deamination) to the urea cycle. In the process, glutamate changes back to 2-ketoglutarate.