There are several basic reaction types that will be encountered repeatedly in cellular processes. It is a good idea to become familiar with these reactions and the terms that describe them. They are grouped in pairs, with one reaction type describing the addition of some chemical group and its partner describing the removal of the same group. Hydrolysis or hydrolytic reactions use the addition of a molecule of water to break apart large molecules. Hydrolysis is used during the process of digestion to break large molecules down into their smaller components.
Hydrolytic reactions are exergonic reactions.
In the hydrolysis of the disaccharide sucrose, the components of water are added 'across the bond' the held the two halves of the sucrose molecule together, forming two smaller monosaccharides, glucose and fructose. If water is added, withoug splitting the molecule in two, for example, if hydrogen and a hydroxyl group are added to the two sides of a double bond, the reaction is called a hydration, rather than a hydrolytic reaction. Dehydration synthesis or condensation reactions are the reverse of hydrolysis. Dehydration synthesis plays an important role in the construction of organic polymers. This is the reaction used to assemble monosaccharides to make complex sugars, and is used to join amino acids to make proteins, or to join nucleotides to make a nucleic acid.