What is the tertiary structure of a protein?

The tertiary structure of a protein is the final folding of a protein into its final shape. It involves interactions between the R-groups of the amino-acids in the polypeptide chain. These interactions are more simply known as 'R-group interactions', and they may take one of four different forms: 

• Hydrophobic - Hydrophillic interactions (bonds between polar and non-polar R groups)

• Hydrogen bonds (weakest of the bonds formed)

• Ionic bonds - stronger than Hydrogen bonds and form between oppositely charged R groups)

• Disulfide bonds (aka Disuflide bridges) - these are covalent and the strongest of the R-group interactions, but only occur between R groups that contain sulfur atoms