Protein comes from the Greek word “proteios”, which means first or primary. Proteins, the building blocks of life, are synthesized in all forms of living cells. Humans have tens of thousands of types of proteins, which are all constructed from a set of 20 amino acids.

Multiple amino acids connected by peptide bonds form a polypeptide. However, it is important to note that the term polypeptide is not synonymous with protein. A functional protein is not just an individual polypeptide chain but actually, one or more polypeptides precisely folded into a unique molecular shape. This specific protein structure determines its final function.


  • OpenStax College, Biology OpenStax CNX. 30 May 2015