Question

What type of interaction would you expect to occur between the following pairs of amino acids? R is where it attaches to the amino acid backbone. SH disulfide bond nonpolar polar salt bridge

The second question has an option of nonpolar as well

Answer 1

Q1. Both amino acids are containing Thiol (-SH) groups. When they're close, the disulfide bond is supposed to take place. Both thiol groups come in closer proximity & oxidation happens to yield disulfide linkage & connect those amino acids. This oxidation reaction requires some external energy that's compensated by the internal energy generation of bond formation. Disulfide bond is typically a stable bond with 251 kJ/mol energy on an average.

Q2. Left amino acid is containing an ammonium (-NH2CH3+)cation whereas right one is containing a carboxylate (-COO-) anion. Since they've opposite charges, it's expected that they'll have polar interaction taking place. This is a sort of intermolecular Zwitter ion-like combination. Zwitter ion pair comprises an ammonium cation & carboxylate anion at the Isoelectric pH of an amino acid is purely intramolecular interaction.

Note: Wherever alkyl chains are present, covalent (non-polar interactions) are supposed to take place. Since it's common & truly weak, so often excluded & other interactions are considered.