The building blocks of protein are amino acids.
Amino acids are a class of organic compounds that contain at least one amino group, -NH2, and carboxyl group, -COOH.
Alpha amino acids , RCH(NH2)COOH, are the building blocks from which proteins are constructed.
The NH group of one amino acid and the COOH group of the other amino acid are joined together and a peptide bond -CONH- is formed between the two amino acids and the product is called a dipeptide.