Which of the following contributes to the three-dimensional structure of proteins?

The three-dimensional structure of proteins, known as tertiary structure, is significantly influenced by various types of interactions among the amino acid side chains. The correct choice highlights three key interactions: hydrogen bonds, ionic bonds, and disulfide bridges.

Hydrogen bonds occur between polar side chains of amino acids, helping to stabilize the protein structure by promoting the folding and shaping of the polypeptide chain. Ionic bonds form between positively and negatively charged side chains, contributing further stability to the overall protein configuration. Disulfide bridges, which are covalent bonds formed between the sulfur atoms of cysteine residues, provide strong links that can hold different parts of the protein together, reinforcing its three-dimensional form.

Together, these interactions create a complex tertiary structure that is essential for the protein's function, as the specific shape determines how a protein interacts with other molecules. The other options, focusing on only one type of bond, do not capture the comprehensive range of interactions that contribute to this complex structure.