Which type of bond forms between the R groups of amino acids in proteins?

The formation of bonds between the R groups of amino acids plays a crucial role in the stabilization and function of proteins. Specifically, disulfide bridges and hydrogen bonds are key types of interactions that occur between the side chains of amino acids.

Disulfide bridges, which are a type of covalent bond, form specifically between the sulfur atoms of cysteine residues when they undergo oxidation. This creates a strong linkage that can significantly stabilize the three-dimensional structure of proteins, particularly in extracellular environments where they may be exposed to varying conditions.

Hydrogen bonds are another common interaction among R groups. They occur when there is a polar covalent bond within the amino acid side chains, allowing for attractions between partial positive and partial negative charges in nearby groups. These interactions are vital for maintaining secondary and tertiary structures of proteins.

In contrast, other bond types listed in the options do not primarily form between R groups in the context described. Peptide bonds specifically link amino acids together in a polypeptide chain but do not occur between R groups. Ionic bonds also can play a role between charged side chains, yet they are not the primary types of bonds forming between R groups, which are primarily stabilized through disulfide bridges and hydrogen bonds. Thus, the correct selection is the