Proteins

• Amino acid:

  • Amine group
  • R-group
  • Hydrogen atom
  • Carboxyl group
• Amino acids are joined by peptide bonds to form dipeptides and polypeptides.
• Test for proteins:

  • Add Biuret A solution to food sample.
  • Add Biuret B solution to mixture.
  • Positive result will be indicated by blue solution turning lilac.
• Primary Structure:

  • Sequence of amino acids forms chain
  • Peptide bonds
  • 2D structure
• Secondary Structure:

  • Chain is folded into beta pleated sheets or alpha helix coils.
  • Hydrogen bonds formed
  • 3D structure
• Tertiary Structure:

  • Folded further.
  • Ionic bonds, disulphide bridges and more hydrogen bonds are formed.
• Quaternary Structure:

  • Many 3D tertiary structures are joined together.