Lysine is one of the 20 amino acids that make up proteins in our body. It is abbreviated to the 3-letters Lys and the 1-letter K. Lysine’s R-group consists of an amino group at the end of a long, 4-carbon chain. As a result, lysine is a polar, hydrophilic amino acid. The nitrogen in the amino group also acts as a proton acceptor, making lysine a basic, positively charged amino acid at physiological pH. 

Key Points

  • Lysine
    • Abbreviations
      • Lys, K
    • Chemical Structure
    • R-group: -CH2-CH2-CH2-CH2-NH2 
    • Polarity
      • Polar (water soluble/hydrophilic)
    • Acidity/Basicity
      • Basic
      • pKa = 10.5 (rounded)
    • Charge at pH 7
      • Positive (+)