Final answer:
When a serine molecule reacts with another serine molecule, they form a peptide bond through a dehydration reaction.
Step-by-step explanation:
When a serine molecule reacts with another serine molecule, they form a peptide bond. A peptide bond is a covalent bond that attaches to each amino acid in a protein chain. It is formed through a dehydration reaction where the carboxyl group of one amino acid combines with the amino group of the incoming amino acid, releasing a water molecule.