9781422280485

Protein

A 3-D chemical model of alanine, one of the nine nonessential amino acids used by the human body.

amino acids, but only 20 of them are used by the human body. Amino acids have specific chemical components in common, including carbon, hydrogen, oxygen, and nitrogen. Each of the 20 amino acids used by the human body has additional components—called a “side chain” or an “R group”—that give it its unique identity. Proteins are made from anywhere from 50 to 2,000 amino acids linked together into chains. The links between the amino acids are called peptide bonds , and the chains are known as polypeptides . Even though there are only 20 base units of amino acids, they make a huge variety of proteins by combining into

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