Examples of antioxidants include vitamins C and E, selenium, and carotenoids, such as beta-carotene, lycopene, lutein, and zeaxanthin. This fact sheet provides basic information about antioxidants, summarizes what the science says about antioxidants and health, and suggests sources for additional information. Key Points Vegetables and fruits are rich sources of antioxidants.
Proteins, among the most complex of all organic compounds, are composed of amino acids (see Figure 2-4), which contain carbon, hydrogen, oxygen, and nitrogen atoms. Certain amino acids also have sulfur atoms, phosphorus, or other trace elements such as iron or copper.
Proteins are composed of Î±-amino acids linked together by peptide bonds into polypeptide chains. An amino acid is characterized by an amino group (-NH2) and a carboxylic acid group (-COOH) linked to a carbon, known as the Î±-carbon. Also attached to the Î±-carbon is a H and various R-groups or side-chains.