amino acids

Amino Acids: Classification by Side Chains

Nonpolar Side Chains

  • Glycine (G):

    • Abbreviation: Gly

    • Structure: H -

    • Properties: Smallest amino acid, nonpolar.

  • Alanine (A):

    • Abbreviation: Ala

    • Structure: H3C -

    • Properties: Nonpolar, hydrophobic, methyl side chain.

  • Valine (V):

    • Abbreviation: Val

    • Structure: H3C - CH

    • Properties: Nonpolar, branched-chain.

  • Leucine (L):

    • Abbreviation: Leu

    • Structure: H3C - CH2 -

    • Properties: Nonpolar, branched-chain.

  • Isoleucine (I):

    • Abbreviation: Ile

    • Structure: H3C - CH -

    • Properties: Nonpolar, branched-chain.

  • Methionine (M):

    • Abbreviation: Met

    • Structure: Contains sulfur in its side chain.

    • Properties: Nonpolar, hydrophobic, initiates protein synthesis.

  • Phenylalanine (F):

    • Abbreviation: Phe

    • Structure: Contains aromatic ring.

    • Properties: Nonpolar, hydrophobic.

  • Tryptophan (W):

    • Abbreviation: Trp

    • Structure: Contains indole structure.

    • Properties: Nonpolar, hydrophobic, precursor for serotonin.

  • Proline (P):

    • Abbreviation: Pro

    • Structure: Cyclic structure that adds rigidity.

    • Properties: Nonpolar, unique, affects protein folding.

Polar Side Chains

  • Serine (S):

    • Abbreviation: Ser

    • Structure: OH attached to side chain.

    • Properties: Polar, hydrophilic, participates in phosphorylation.

  • Threonine (T):

    • Abbreviation: Thr

    • Structure: Contains a hydroxyl group.

    • Properties: Polar, hydrophilic, essential amino acid.

  • Cysteine (C):

    • Abbreviation: Cys

    • Structure: Contains a thiol (-SH) group.

    • Properties: Polar, capable of forming disulfide bonds, stabilizes protein structure.

  • Tyrosine (Y):

    • Abbreviation: Tyr

    • Structure: Contains a hydroxyl group attached to a benzene ring.

    • Properties: Polar, participates in signal transduction.

  • Asparagine (N):

    • Abbreviation: Asn

    • Structure: Amide side chain.

    • Properties: Polar, hydrophilic, involved in N-glycosylation.

  • Glutamine (Q):

    • Abbreviation: Gln

    • Structure: Longer amide side chain than asparagine.

    • Properties: Polar, hydrophilic, plays a role in nitrogen metabolism.

Acidic Side Chains

  • Aspartate (D):

    • Abbreviation: Asp

    • Structure: Contains a carboxyl group.

    • Properties: Acidic, negatively charged at physiological pH.

  • Glutamate (E):

    • Abbreviation: Glu

    • Structure: Similar to aspartate with an extra carbon.

    • Properties: Acidic, negatively charged at physiological pH.

Basic Side Chains

  • Lysine (K):

    • Abbreviation: Lys

    • Structure: Contains an amino group.

    • Properties: Basic, positively charged at physiological pH.

  • Arginine (R):

    • Abbreviation: Arg

    • Structure: Contains a guanidinium group.

    • Properties: Basic, positively charged at physiological pH, important in nitric oxide synthesis.

  • Histidine (H):

    • Abbreviation: His

    • Structure: Contains an imidazole ring.

    • Properties: Basic, can be positively charged depending on the pH, important in enzyme active sites.