Bonds in Protein Structures

Steps:

• Primary structure consists of amino acids linked by peptide bonds, forming the polypeptide chain.
• Secondary structure features local folding, such as alpha helices and beta sheets, stabilized by hydrogen bonds between backbone atoms.
• Tertiary structure involves the overall 3D folding of the chain, maintained by interactions like ionic bonds between charged side chains.
• Compare options: only C correctly matches peptide bonds to primary, hydrogen bonds to secondary, and ionic bonds to tertiary.

Why C is correct:

• Peptide bonds covalently link amino acids in the primary sequence; hydrogen bonds stabilize secondary motifs per the definition of alpha helices and beta sheets; ionic bonds form salt bridges that lock tertiary structure.

Why the others are wrong:

• A: Peptide bonds occur in primary structure, not tertiary.
• B: Ionic bonds stabilize tertiary folding, not secondary.
• D: Ionic bonds are for tertiary, while secondary uses hydrogen bonds.

Final answer: C