Amino Acids

  • 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


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