Biological molecules tutorial: Protein structure (key points covered)

1) Primary structure
- number, type, and sequence of amino acids
- held together by peptide bonds
- determines the type of bonding possible in secondary/tertiary/quaternary structure

2) Secondary structure (alpha-helix or beta-pleated sheet)
- folding and coiling of polypeptide backbone
- hydrogen bonds
- between neighbouring amino acids at peptide bond regions

3) Tertiary structure
- further coiling and folding to form a compact three-dimensional globular structure
- all four types of intramolecular bonding possible (hydrogen bonds, disulfide bridges, ionic bonds, hydrophobic/hydrophilic interactions)
- between R groups of amino acids

4) Quaternary structure
- aggregation of 2 or more extensively coiled polypeptide chains
- held together by four possible types of intermolecular bonds (hydrogen bonds, disulfide bridges, ionic bonds, hydrophobic/hydrophilic interactions)