Final answer:
Molecules 7 and 8 could be joined together by a peptide bond through a dehydration reaction.
Step-by-step explanation:
In the process of peptide bond formation, the carboxyl group of one amino acid is joined to the amino group of another amino acid, resulting in the formation of a peptide bond and the release of a water molecule. Based on the given options, molecules 7 and 8 could be joined together by a peptide bond through a dehydration reaction.