Identify the type of structure (primary, secondary, tertiary, or quaternary) that corresponds to the following statements.
(a) This type of structure is the amino acid sequence in the protein.
(b) This type of structure indicates how different peptide chains in the overall protein are arranged with respect to one another.
(c) This type of structure refers to how the polypeptide chain is folded, including how amino acids that are far apart in the sequence end up in the overall molecule.
(d) This type of structure deals with structures that arise from hydrogen bonding between amide groups in the protein’s backbone.