Amino acids with a uncharged polar side chain. Amino acids with a nonpolar side chain. Amino acids consist exclusively of the L-isomer . Normally there is free rotation about the C-N bond in amino acids. In proline and hydroxyproline, this free rotation is prevented.
Cystine can form covalent bonds to another cystine.
Protein shape is determined mostly by the amino acid sequence. Amino acids are covalently bonded from the carboxyl carbon of one amino acid to the amino nitrogen of another amino acid. The planar arrangement of of 6 atoms in the result of resonance. Proteins consist of a polypeptide backbone with attached side chains. The three dimension folding of proteins is the result of specific interactions between side chains.