1. Protein structure

Figure 2a: Chemical structure of the 20 amino acids (nonpolar; polar) Figure 2b: Chemical structure of the 20 amino acids (nonpolar; polar)

Figures 2a and 2b: Chemical structure of the 20 amino acids (nonpolar; polar)

1.1 Amino acids

Classification

Amino acids are classified according to the charge of their residue:

  • Hydrophobic amino acids
    Gly, Ala, Val, Leu, Ile, Met, Phe, Trp, Pro

  • Neutral amino acids (non-charged but polar)
    No ionisable groups in the residue
    Ser, Thr, Cys, Asn, Gln, Tyr

  • Acidic amino acids (negatively charged at a physiological pH)
    –COOH group in the residue, ionised into –COO- at a cellular pH
    Asp, Glu