USMLE

Arginine

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Amino Acids
  1. Serine
  2. Asparagine
  3. Alanine
  4. Valine
  5. Leucine
  6. Isoleucine
  7. Phenylalanine
  8. Tryptophan
  9. Methionine
  10. Proline
  11. Glycine
  12. Threonine
  13. Cysteine
  14. Tyrosine
  15. Glutamine
  16. Aspartate
  17. Glutamate
  18. Histidine
  19. Lysine
  20. Arginine

Summary

Arginine is one of 20 amino acids that make up proteins in our body. It is abbreviated to the 3-letter Arg and the 1-letter R. Arginine’s R-group starts with a 3-carbon chain, followed by a guanidino group, which is a three-pronged structure with nitrogens at the end of each prong. As a result of these nitrogens, arginine is a polar, hydrophilic amino acid. The double bonded nitrogen also acts as a proton acceptor, making arginine a basic, positively charged amino acid at physiological pH.

Key Points

  • Arginine
    • Abbreviations
      • Arg, R
    • Chemical Structure
    • R-group: -CH2-CH2-CH2-Guanidino
    • Polarity
      • Polar (water soluble/hydrophilic)
    • Acidity/Basicity
      • Basic
      • pKa = 12.5 (rounded)
    • Charge at pH 7
      • Positive (+)