Hydrolysis reactions involve

• A. Water out, energy in
• B. Water in, energy in
• C. No water involved, energy out
• D. Water in, energy out

Answer: (D)

Hydrolysis involves adding water to a molecule to break a bond. In many biological cases, that bond-breaking releases energy, providing power for cellular processes. So water is in the reaction and energy is released, which is captured by the description: water in, energy out. This contrasts with setups where water would be removed (dehydration/condensation) or where the reaction requires an input of energy (endergonic). A common example is ATP hydrolysis, which liberates energy to drive work in the cell.