Difference Between Hydrolysis and Dehydration

Hydrolysis vs Dehydration

Water is very important for the survival of living beings. It has many usages. When water is not in sufficient quantities, it affects many important reactions in the bodies.


This is a reaction where a chemical bond is broken using a water molecule. During this reaction, a water molecule splits up into a proton and a hydroxide ion. Then these two ions are added to two parts of the molecule where the bond is broken. For example, following is an ester. The ester bond is between –CO and –O.


In the hydrolysis, the proton from the water adds to the –O side, and the hydroxide ion adds to the –CO side. Therefore, as a result of the hydrolysis, an alcohol and a carboxylic acid will form which were the reactants when forming the ester.

Hydrolysis is important to break down the polymers which were made by condensation polymerization. Condensation polymerizations are a type of chemical reaction where small molecules get together to form a large single molecule. The reaction takes place within two functional groups in the molecules. Other characteristic feature of a condensation reaction is that, during the reaction, a small molecule like water is lost. So, hydrolysis is the reversible process of the condensation polymerization. The above example shows a hydrolysis of an organic molecule.

Most of the hydrolysis reactions of organic molecules have to be catalyzed with strong acids and bases. However, simply, when a salt of a weak acid or weak base is dissolved in water, it also undergoes hydrolysis. Water ionizes and also the salt dissociates into a cation and anion. For example, when sodium acetate is dissolved in water, acetate reacts with protons and form acetic acid whereas sodium interacts with hydroxyl ions.

In living systems, hydrolysis reactions are very common. In the digestive system, this takes place in order to digest the food that we intake. Generating energy from ATP is also due to a hydrolysis reaction of the pyrophosphate linkages. Most of these biological hydrolysis reactions are catalyzed with enzymes.


Dehydration is the condition in which there isn’t the normal level of water required. When referred to biological systems, this is caused by a severe loss of body fluid (for example, blood). There are three types of dehydration as hypotonic, hypertonic and isotonic. Since the electrolytes level is directly affecting the water level, it is important to maintain the electrolyte balance within the body in order to maintain the osmotic balance.

Dehydration can be caused in several ways. Excess urine passing, diarrhea, loss of blood due to accidents, and excessive sweating are some of the common ways. Dehydration can cause headaches, decreased blood pressure, dizziness, fainting. In extreme condition of dehydration, it causes unconsciousness, and death.

Dehydration can be prevented by drinking sufficient water. When lot of water is lost from the body, it should be re-supplied (oral rehydration, injection etc).


What is the difference between Hydrolysis and Dehydration?

• Dehydration is the condition of having less amount of water than the normal level.

• Hydrolysis is a reaction where a chemical bond is broken using a water molecule.

• Dehydration affects hydrolysis reactions because for the hydrolysis reactions to take place there should be water.