Proteins are complex organic compounds.
The basic structure of protein is a chain of amino acids that contain carbon, hydrogen, oxygen, and nitrogen. The presence of nitrogen differentiates protein from carbohydrate and fat . The human body requires approximately 20 amino acids for the synthesis of its proteins. They are, in fact, essential but people do not have to get them from food we eat. There are 9 essential amino acids that are obtained only from food, and not made in the body.