Outline the first three levels of protein structure, including the types of bonding within each

The primary structure of a protein is its amino acid sequence which is determined by the base sequence of the gene which codes for the protein. Secondary structures include alpha-helicies and beta-pleated sheets. These structures form as a result of hydrogen bonds between the peptide groups of the amino acids. Tertiary structure develops the 3D shape of the protein due to non-covalent interactions between side groups (R groups) of the amino acid chain. Examples include; disulphide bridges which form between sulphur atoms on the R groups of the amino acid cysteine, hydrogen bonds form between polar R groups and ionic bonds form between oppositely charged R groups.