Amino << uh MEE noh >> acid is the name for the type of organic acids that make up all the proteins in living things. Scientists call amino acids the building blocks of proteins. All amino acids contain carbon, hydrogen, oxygen, and nitrogen. Some amino acids contain sulfur.
Green plants and some microorganisms can make all the amino acids they need. But human beings and higher animals cannot make all of the 20 amino acids their bodies need to build tissues. Humans must get at least nine amino acids from their food. Protein foods, such as eggs, meat, milk products, and some vegetables, provide amino acids. The body breaks down these foods into amino acids. It then links the amino acids to form new proteins.
The body can make many different kinds of proteins. A single protein may consist of several hundred amino acid units linked together by chemical bonds. Also, the order of the amino acids may vary, producing different proteins. These different amino acid sequences determine the functions of the proteins.
Some simple proteins may be made up of only four different kinds of amino acids. Most of the more complex proteins contain about 20 amino acids. All amino acids contain one or more groups of one nitrogen and two hydrogen atoms called amino groups. Amino acids are made up of amino groups and certain organic acids.
See also Protein; Cell (The work of a cell); Hormone (How hormones work).
