• Only l-amino acids are found in proteins.
• Essential
  • PVT TIM HaLL: Phenylalanine, Valine, Tyrosine, Threonine, Isoleucine, Methionine, Histidine, Leucine, Lysine.
  • Glucogenic: Methionine, histidine, valine. I met his valentine, she is so sweet (glucogenic).
  • Glucogenic/ketogenic: Isoleucine, phenylalanine, threonine, tyrosine.
  • Ketogenic: Leucine, Lysine. The onLy pureLy ketogenic amino acids (supplemented in pyruvate dehydrogenase deficiency)
• Essential amino acids for low birth weight infants
  • Cysteine, arginine, taurine
• Acidic
  • Aspartic acid, glutamic acid.
  • Negatively charged at body pH.
• Basic
  • Arginine, histidine, lysine.
  • Arginine is most basic. Histidine has no charge at body pH.
  • Arginine and histidine are required during periods of growth.
  • Arginine and lysine are ↑ in histones which bind negatively charged DNA.
  • His lys (lies) are basic.
• Neutral
  • Alanine, Serine, Threonine, Valine, Isoleucine, Leucin, Phenylalanine, Tyrosine, Tryptophan
  • Found in urine in Hartnup disease
• Nonpolar
  • Alanine, Valine, Leucine, Isoleucine, Phenylalanine, Tryptophan, Methionine, Proline, Glycine
• Amino acid derivatives
• Methionine → cysteine, carnitine, taurine & lecithin
• Choline + acetyl-CoA (with enzyme choline acetyltransferase) → Acetylcholine
• Glutamine (with enzyme glutaminase) → Glutamate (with enzyme glutamate decarboxylase & Vitamin B6) →  GABA
• Aromatic amino acids:
  • Phenylalanine – benzene ring;
  • Histidine – Imidazole ring;
  • Tryptophan – Indole ring;
  • Proline contains a ring structure, but is not classified as an aromatic amino acid