The amino acids structure states that the amino acids are important and the basic unit of protein. They are the ones which consist of amino group and carboxylic group. They also play extensive role in the processes of gene expression that includes adjustment of protein function, which facilitates the messenger RNA translation. In nature, around 700 types of the amino acids are uncovered. Almost all of them are as a-amino acid. They are discovered in the algae, fungi, bacteria and different other plants. They are put together in polypeptide chain on ribosome during the protein synthesis. In process of peptide bond, covalent bond between the two amino acid residues is formed.
There are around twenty amino acids as per list of amino acids which occurs commonly in the nature. All of them include all specific features that are defined by side chain and that offers complete unique role in protein structure. Based on prosperity of side chain for being in contact with the polar solvent as water, it can be classified as the hydrophobic, polar or even charged. This charged amino acids residue includes the lysine, aspartate, arginine and even glutamate. The polar amino acid also includes the threonine, serine, glutamine, asparagine, tyrosine and histidine. The amino acids include the proline, isoleucine, leucine, valine, alanine, methionine, cystenine, tryptophane.
You must have noticed probably that all these classifications are based on amino acid side chain types. However, the glycine as common amino acid don’t have side chain and for such a reason it is not straightforward for assigning it one of above classes. Generally, it is also found at protein surface, within the coil or loop regions, offering high flexibility to polypeptide chain at such locations. The amino acids structure suggests that they are rather hydrophilic. Similarly, proline on other hand is non-polar generally and found buried inside protein, similar to the glycine. It is found in the loop regions.
Contrast to the glycine, it offers the rigidity to polypeptide chains by imposing of some torsion angles on structure segment. Reason for it is also discussed in action on the torsion angles. The proline and glycine is highly conserved within protein family since they all are essential for conservation of specific protein folds. You must also know that these twenty amino acids are present in big molecules as the essential component of protein and peptides, amines, basic structure, acidic structure or other amide types.