The enzymes that are central to every single biological reaction are proteins. Anti-bodies, many hormones, muscles and bones all contain protein. The Building Blocks of Protein Humans don't have a requirement for protein per se. The requirement is for amino acids, which are the building blocks of protein, and for the nitrogen they contain. A protein molecule consists of long twisted strands or chains of amino acids.
Every amino acid contains nitrogen, which is found primarily in amino acids.
There are only about 20 different amino acids in foods. But amino acids are like the letters of the alphabet. We can produce thousands of words by rearranging the same 26 letters into different combinations. In the same way, the body can produce thousands of proteins by linking amino acids in different sequences. When food proteins enter the body, they are broken down into individual amino acids.