The secondary structure of a protein is the
◦ configuration of those parts of the chain stabilized by a regular pattern of covalent bonds between C and O groups of the backbone of the chain.
◦ configuration of those parts of the chain stabilized by a regular pattern of hydrogen bonds between CO and NH groups of the backbone of the chain.
◦ specific order of amino acids in the chain.
◦ overall three-dimensional structure of the molecule.
◦ overall arrangement of several polypeptide chains into one functional unit.