Amino acids

Amino acids are the basic monomers and building blocks of proteins (polymers). Their structure consists of three main groups as seen in Figure 1, namely the amino group or N terminus, carboxyl group or C terminus and the R group which contains the functional component of the amino acid. The R group gives the amino acid specific features according to its polarity and charge, which then affect the chemical and biological properties of the protein.

There are a total of 21 amino acid types based on their different R groups. 12 of these can be synthesized in the body, while the other 9 must be consumed in the diet, hence are termed essential amino acids.

Protein structure can be divided into four main categories depending on level of complexity.

* Primary structure: Peptide bonds between amino acids form a straight chain of peptides called a polypeptide, the primary structure.

* Secondary Structure: Formation of hydrogen bonds between this initial structure leads to the formation of the secondary protein structure. Amino acid sequences will commonly fold into two stable configurations of secondary structures

• Alpha helices occur when the amino acid sequence folds into a coil / spiral arrangement

• Beta-pleated sheets occur when the amino acid sequence adopts a directionally-oriented staggered strand conformation

* Tertiary Structure: Folding of this polypeptide chain into a 3D shape forms the tertiary structure.

* Quarternary Structure: The combination of multiple different polypeptide chain leads to formation of the quaternary structure.