## Human Anatomy & Physiology (9th Edition)

Dehydration synthesis reactions combine two molecules by removing a hydrogen from one molecule and a hydroxyl group from the other, thus removing a water molecule ($H_2O$). Hydrolysis reactions add a water molecule to break apart a larger molecule into two smaller molecules, with one receiving a hydrogen and one a hydroxyl group. Dehydration synthesis and hydrolysis are used in countless reactions within the body, including digestion of food molecules through hydrolysis and the synthesis of proteins and carbohydrates through dehydration reactions.