A condensation reaction is a type of chemical reaction in which monomers (small molecules) join together to form polymers (large molecules or macromolecules).During this process, covalent bonds form between the monomers, allowing them to join together into polymers. As these bonds form, water molecules are removed (or lost).

You may also hear this process referred to as dehydration synthesis. Dehydration means to remove water (or loss of water - think what happens when you say you are dehydrated). Synthesis in biology refers to the creation of compounds (biological molecules).

In the physical world, condensation is often seen in the form of the water cycle, where water changes from a gas to a liquid. However, in biology, condensation does not mean that biological molecules turn from gases into liquids. Instead, it means the chemical bonds between molecules form with the elimination of water.

Condensation reactions are important for infection. During an infection, the body's immune system produces antibodies to fight off the invading pathogen. These antibodies are created through a condensation reaction, where two monomers join together to form a larger molecule.

What is the general equation of a condensation reaction?

The general equation of condensation goes as follows: A and B are stand in symbols for the molecules that are condensed, and AB stands for the compound produced from the condensation.

What is an example of a condensation reaction?

Let's use the combination of galactose and glucose as an example of condensation reaction.

Both galactose and glucose are simple sugars, also known as monosaccharides. When they undergo a condensation reaction, lactose is formed. Lactose is also a sugar, but it's a disaccharide, which means it consists of two monosaccharides: glucose and galactose joined by a chemical bond known as a glycosidic bond (a type of covalent bond).

Although their formula is the same, the difference lies in their molecular structures. It's important to observe the -OH on the 4th carbon atom in Figure 1.

‍

If we remember the general equation of condensation, it goes as follows:

Now, let us swap A and B (groups of atoms) and AB (a compound) with galactose, glucose, and lactose formulas, respectively:

Notice that both molecules of galactose and glucose have six carbon atoms (C6), 12 hydrogen atoms (H12), and six oxygen atoms (O6).

As a new covalent bond forms, one of the sugars loses a hydrogen atom (H), and the other loses a hydroxyl group (OH). From these, a molecule of water is formed (H + OH = H2O).

Since a water molecule is one of the products, the resulting lactose has 22 hydrogen atoms (H22) instead of 24 and 11 oxygen atoms (O11) instead of 12.

The diagram of condensation of galactose and glucose would look like this:

‍

The same process occurs in other condensation reactions, where monomers combine to form polymers and covalent bonds are created.

This means that:

When monosaccharides undergo a condensation reaction, covalent glycosidic bonds are formed between them. In our earlier example, two monosaccharides joined to form a disaccharide. If multiple monosaccharides combine, a polysaccharide (or complex carbohydrate) polymer is formed.

When amino acid monomers undergo a condensation reaction, polypeptide (or protein) polymers are created, joined together by a covalent bond called a peptide bond.

When nucleotide monomers undergo a condensation reaction, a covalent bond called a phosphodiester bond is formed between them, resulting in polynucleotide (or nucleic acid) polymers.

Even though fatty acids and glycerol are not monomers, lipids still form during condensation reactions. When fatty acids and glycerol undergo a condensation reaction, an ester bond is created to form lipids.

It's important to note that condensation reactions are opposite to hydrolysis reactions. During hydrolysis, polymers are broken down rather than formed. Besides, water is not removed but added in a hydrolysis reaction.

What is the purpose of a condensation reaction?

In summary, a condensation reaction is a chemical process where monomers join together to form polymers, creating covalent bonds between the monomers and releasing water in the process. This reaction is crucial in the formation of essential macromolecules such as carbohydrates, proteins, lipids, and nucleic acids, which play important roles in the functioning of living organisms. Without condensation reactions, these essential functions would not be possible.

What is a condensation reaction?

Condensation is a chemical reaction during which monomers (small molecules) covalently bond to form polymers (large molecules or macromolecules).

What happens in a condensation reaction?

In a condensation reaction, covalent bonds form between monomers, and as these bonds form, water is released. This all results in the formation of polymers.

How does a condensation reaction differ from a hydrolysis reaction?

In a condensation reaction, covalent bonds between monomers form, while in hydrolysis, they break. Also, water is removed in condensation while it is added in hydrolysis. The result of condensation is a polymer, and of hydrolysis is the breaking down of a polymer into its monomers.

Is condensation a chemical reaction?

Condensation is a chemical reaction because chemical bonds are formed between monomers when forming polymers. Also, it is a chemical reaction because monomers (reactants) convert into a different substance (product) that is a polymer.

What is condensation polymerisation reaction?

Condensation polymerisation is the joining of monomers to form polymers with releasing a by-product, usually water. It is different from addition polymerisation, which creates no by-products other than a polymer when monomers join.

‍