複選題24. Which of the following descriptions regarding proteins is (are) CORREСТ? (A) Proteins are made up of amino acids. (B) Due to the polar and nonpolar properties of amino acid side chains, both hydrophilic and hydrophobic patches can form within a single protein. (C) Alpha-helix and beta-sheet are secondary structures of a protein; in addition to peptide bonds, covalent linkages are required to form both alpha-helices and beta-sheets. (D) The majority of enzymes are proteins. (E) Due to differences in the properties of amino acids, proteins can be positively or negatively charged.