Glycosidic Bond Formation | Linkages formed between Carbohydrate Monomers

Sugar molecules are connected to each other by condensation reaction. This type of linkage is known as a Glycosidic Linkage and the bonds formed are called Glycosidic Bonds.

Example 1: Maltose

An example of a glycosidic linkage is the bonding between two glucose molecules.

In the example above, the hydroxyl groups of the two monomers result in a water molecule given off and one oxygen atom connecting the two monomers. The two sugar molecule connected by a glycosidic bond to form a disaccharide. In this case, the disaccharide is made up of two α-glucose molecules.

An α-glycosidic bond is formed here because the number one carbon was in the alpha position – this means, the OH-group of the number one carbon is opposite site of the plane as the number six carbon. The result linkage is called α – 1, 4 glycosidic linkage.

Example 2: Sucrose

The next example of a glycosidic bond is between glucose and fructose.

This glycosidic linkage also result in the formation of an alpha linkage since the number one carbon of the glucose molecule is in the alpha position here as well. The result linkage is called α – 1, 2 glycosidic linkage.

These are single monomer units. “Mono” means one and “Saccharide” is another name for sugar. Monosaccharide is carbohydrate in its simplest form. Some examples of monosaccharides are glucose and fructose.

These are sugars that consist of two monosaccharide units. “Di” means two. Hence, a disaccharide is a combination of two sugars. Examples are Maltose and Sucrose.

“Oligo” means few. Oligosaccharides are sugars that consist of few monomer units, usually 3 to 10 monomer monosaccharide units.  An example of oligosaccharide is Fructo-oligosaccharides, FOS for short. FOS can be found in many vegetables.

In this case “Poly” means “Many sugars”. Polysaccharides are made up of hundreds to hundreds of thousands of monosaccharide units. An example of a polysaccharide is cellulose.

Long chains of simple sugars are also called Complex Carbohydrates – usually carbohydrates made from linking three or more monosaccharides.