What is a hydrolysis reaction?

• A. H2O added, covalent bond forms
• B. H2O leaves, covalent bond forms
• C. H2O leaves, ionic bond forms
• D. H2O added, ionic bond forms

Answer: (A)

Hydrolysis is the process of breaking a covalent bond in a molecule by adding water. The water molecule donates a hydrogen to one fragment and a hydroxyl group to the other, so a new covalent bond forms between the fragments and the water-derived pieces, effectively splitting the original bond. That’s why describing it as water added with a covalent bond forming fits best. The alternative idea of water leaving corresponds to dehydration synthesis, not hydrolysis, and forming ionic bonds isn’t how hydrolysis typically occurs in biology.