What maintains the secondary structure of a protein?

• A. Ionic bonds
• B. Hydrophobic interactions
• C. Disulfide bridges
• D. Hydrogen bonds

Answer: (D)

Verified step by step guidance

1. Understand that proteins have different levels of structure: primary, secondary, tertiary, and quaternary. The secondary structure refers to the local folded structures that form within a polypeptide due to interactions between atoms of the backbone.
2. Recognize that the secondary structure of a protein is primarily maintained by hydrogen bonds. These bonds occur between the carbonyl oxygen of one amino acid and the amide hydrogen of another.
3. Identify the two most common types of secondary structures: alpha helices and beta sheets. In an alpha helix, the hydrogen bonds form between every fourth amino acid, creating a coiled structure. In a beta sheet, the hydrogen bonds form between strands, which can be parallel or antiparallel.
4. Differentiate hydrogen bonds from other types of interactions such as ionic bonds, hydrophobic interactions, and disulfide bridges. Ionic bonds and hydrophobic interactions are more relevant to tertiary structure, while disulfide bridges are covalent bonds that stabilize tertiary and quaternary structures.
5. Conclude that while other interactions contribute to the overall stability and folding of proteins, hydrogen bonds are specifically responsible for maintaining the secondary structure, such as alpha helices and beta sheets, within the protein.