Hydrolysis: Definition and Examples

Understand Hydrolysis in Chemistry

Human protein phosphatase
Human protein phosphatase removes a phosphate group from its substrate by hydrolysing phosphoric acid monoesters into a phosphate ion and a molecule with a free hydroxyl group. Laguna Design / Getty Images

Hydrolysis definition: Hydrolysis is a type of decomposition reaction where one reactant is water. Typically, water is used to break chemical bonds in the other reactant. The term comes from the Greek prefix hydro- (meaning water) with lysis (meaning to break apart).

Hydrolysis may be considered the reverse of a condensation reaction, in which two molecules combine with each other, producing water as one of the products.

The general formula of a hydrolysis reaction is:
AB + H2O → AH + BOH

Organic hydrolysis reactions involve the reaction of water and an ester. This reaction follows the general formula:
RCO-OR' + H2O → RCO-OH + R'-OH
The hyphen on the left side denotes the covalent bond that is broken during the reaction.

The first commercial application of hydrolysis was in the making of soap. The saponification reaction occurs when a triglyceride (fat) is hydrolyzed with water and a base (usually sodium hydroxide, NaOH, or potassium hydroxide, KOH). The reaction produces glycerol. Fatty acids react with the base to produce salts, which are used as soap.

Hydrolysis Examples

Dissolving a salt of a weak acid or base in water is an example of a hydrolysis reaction. Strong acids may also be hydrolyzed. For example, dissolving sulfuric acid in water yields hydronium and bisulfate.

Hydrolysis of a sugar has its own name: saccharification. For example, the sugar sucrose may undergo hydrolysis to break into its component sugars, glucose and fructose.

Acid-base catalyzed hydrolysis is another type of hydrolysis reaction. An example is the hydrolysis of amides.

In biological systems, hydrolysis tends to be catalyzed by enzymes. A good example is the hydrolysis of the energy molecule adenosine triphosphate, or ATP. Catalyzed hydrolysis is also used for digestion of proteins, carbohydrates, and lipids.