Where would you find ionic bonds in biomolecules?
You would be most likely to find ionic bonds in proteins.
Proteins consist from long strings of amino acids held together by peptide linkages.
Some of these amino acids have acidic side-chains ( aspartic and glutamic acid).
Others have basic side-chains (lysine, arginine, and histidine).
In the protein, these side-chains hang off from the backbone of the peptide chain.
Many of the acidic side-chains exist as carboxylate ions, R-COO⁻.
Many of the basic side-chains exist as ammonium ions, R-NH₃⁺.
If these oppositely charged groups in different parts of the chain get close to each other, they can form ionic bonds.
Ionic bonds are one of the forces that are responsible for the three-dimensional shapes of proteins.