Protein is essential for life. It is made up of long chains of amino acids that are linked together through a process called protein synthesis. Amino acids are the basic structural units or "building blocks" that are used to build protein in the human body. There are 20 standard amino acids that are used to build protein. The amino acid sequence of the chain, not just the presence of individual amino acids, determines the structure and function of the resulting protein. Our bodies can produce some of these amino acids internally, but others must be obtained through diet because they cannot be synthesized by the human body. These amino acids are known as "essential amino acids" and must be consumed.