Proteins

• Describe the general structure of an amino acid

  COOH = carboxyl group

  R = variable side chain / group

  H2N = amine group
• Describe how amino acids join together

  Condensation reaction

  Removing a water molecule

  Between carboxyl / COOH group of one and amine / NH2 group of another

  Forming a peptide bond
• What are dipeptides and polypeptides

  Dipeptide 2 amino acids joined together

  Polypeptide many amino acids joined together
• Describe the primary structure of a protein

  Sequence of amino acids in a polypeptide chain, joined by peptide bonds
• Describe the secondary structure of a protein

  Folding (repeating patterns) of polypeptide chain eg.

  alpha helix / beta pleated sheets

  Due to hydrogen bonding between amino acids

  Between NH (group of one amino acid) and C=O (group)
• Describe the tertiary structure of a protein

  • 3D folding of polypeptide chain
  • Due to interactions between amino acid R groups
  • Forming hydrogen bonds, ionic bonds and disulfide bridges
• Describe the quaternary structure of a protein

  • More than one polypeptide chain
  • Forming interactions between polypeptides
• Describe the test for proteins

  1. Add biuret reagent
  2. Positive result is purple/lilac colour