Protein structures

• Primary structure:

  • A sequence of amino acids joined by peptide bonds
• Secondary structure:

  • 2D folding of a chain of amino acids into an alpha helix or a beta pleated sheet, held together by hydrogen bonds
  • Alpha helix - H bonds between amino and carboxyl group, for every 4th amino acid
  • Beta pleated sheet - H bonds between the amino group and carboxyl group
• Tertiary structure:

  • 3D folding of the secondary structure, due to the interactions between the R groups of the polypeptide
  • Hydrogen bonds - forces of attraction between polar R groups
  • Disulfide bridges - covalent bonds between sulfur atoms in cysteine
  • Ionic bonds - between oppositely charged R groups
• Quaternary structure:

  • More than one polypeptide chain folding
• Hydrogen bonding broken by:

  • ��
• Ionic bonding broken by:

  • pH