Amino acids is a chemical compounds produced by living organisms. Many amino acids are the structural units of proteins. These compounds are called amino acids because each of them contains at least one amino group (an atom of nitrogen and two atoms of hydrogen bonded together chemically).
Although more than 150 amino acids have been identified, only some 20 serves as “building blocks” of protein. Protein molecules consist of about 50 to more than 3,000 amino acid molecules linked together. When proteins are digested, they are broken down into their constituent amino acids. Proteins differ from one another because of their amino acids.
Amino acids are used by the body to make tissues, enzymes, hormones, and other vital body substances, and are necessary for the repair of tissues. Most plants are able to produce all the amino acids they need. Animals cannot manufacture all the amino acids they require and must obtain the remainder from their food.
Amino acids that are not produced by animal bodies but that are necessary for proper nutrition are called essential amino acids. Human beings produce only about 12 of the amino acids they need. Among the essential amino acids required by humans are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Many amino acids can be obtained in pure form, either by isolating them from proteins or by synthesizing them. They are used as dietary supplements and for experimental studies in nutrition.