How are amino acids, polypeptides, and proteins related?

1 Answer

Amino acids are all the building blocks of protein. Chain of amino acids form polypeptide. One or more polypeptide (sometimes along with non protein part) together may acquire a functional form and 3D structure to become protein.


A protein is a macromolecule composed of amino acid monomers.

Amino acids contains a central carbon atom bonded to a hydrogen atom, an amino group, a carboxyl group and a variable R group.

Note that the R group are also known as side chains. As all amino acids have the same underlying structure, the distinctive shape and properties of an amino acid (and thus the proteins formed) are determined by the R group.


Polypeptides are polymers composed of many amino acids linked together by peptide bonds. Peptide bond forms between carboxyl group of one amino acid and amino group of another, and it is a dehydration reaction.

Amino acid sequence determines primary protein structure. Polypeptide develops disulphide bonds and thus secondary structure of protein is generated. Further 3D arrangement of polypeptide (by folding) is essential to make a protein functional.