Difference Between Glycosidic Bond and Peptide Bond

Main Difference – Glycosidic Bond vs Peptide Bond

Carbohydrates and proteins are essential components for the human body. Our body uses carbohydrates in order to fulfill the energy requirement. We need proteins for our growth. Carbohydrates and proteins are complex compounds that are made out of small units. The building blocks of carbohydrates are monosaccharides. The building blocks of proteins are amino acids. Monosaccharides are attached to each other through glycosidic bonds forming complex carbohydrates. Amino acids are attached to each other through peptide bonds forming a protein. The main difference between glycosidic bond and peptide bond is that a glycosidic bond is formed when two carbon atoms of two different monosaccharides are linked together whereas a peptide bond is formed when a carbon atom of one amino acid is linked to a nitrogen atom of a different amino acid.

Key Areas Covered

1. What is Glycosidic Bond
      – Definition, Formation, Properties
2. What is Peptide Bond
      – Definition, Formation, Properties
3. Similarities Between Glycosidic Bond and Peptide Bond
      – Outline of Common Features
4. What is the Difference Between Glycosidic Bond and Peptide Bond
      – Comparison of Key Differences

Key Terms: 1,4-Glycosidic Bond, 1,6-Glycosidic Bond, Carbohydrate, Covalent Bond, Glycosidic Bond, Monosaccharide, Peptide Bond, Poly Peptide, Protein

What is a Glycosidic Bond

A glycosidic bond is a type of covalent bond that occurs between two monosaccharides. This bond can be found in sugar or carbohydrate molecules. Carbohydrates are made of monosaccharides that are linked together through glycosidic bonds. A glycosidic bond is formed between two carbon atoms. Here, one carbon atom is linked to another carbon atom via an oxygen atom.

Figure 01: Formation of a Glycosidic Bond between Glucose and Fructose

The number of glycosidic bonds a certain carbohydrate has is dependent on the number of monosaccharides present in that carbohydrate and type of the carbohydrate. For example, in linear carbohydrate molecules, the monosaccharides are linked to each other in their two sides; thus, the number of glycosidic bonds present in that complex is equal to the value of the number of monosaccharides minus one.

If two monosaccharides are bonded via a glycosidic bond, a disaccharide is formed. If several monosaccharides are bonded to each other, an oligosaccharide is formed, and if the number of monosaccharides that are bonded to each other is more than 50, then a polysaccharide is formed. Sometimes, a glycosidic bond may found as a N-glycosidic bond or a S-glycosidic bond. This is because the two carbon atoms here are bonded to each other via a nitrogen atom or a sulfur atom, respectively.

There are two main types of glycosidic bonds that can be formed in between monosaccharides.

• 1,4-glycosidic bond
• 1,6-glycosidic bond

Figure 02: Two Types of Glycosidic Bonds

1,4-glycosidic bond is formed when the –OH group attached to the first carbon of a monosaccharide undergoes condensation reaction with the –OH group attached to the 4th carbon of another monosaccharide. 1,6-glycosidic bond is formed when the –OH group attached to the first carbon of a monosaccharide undergoes condensation reaction with the –OH group attached to the 6th carbon of another monosaccharide. In both methods, a water molecule is formed for each glycosidic bond that is formed.

1, 4-glycosidic bond causes the formation of a linear chain carbohydrate. 1, 6-glycosidic bond causes the formation of carbohydrates having branched structures. However, hydrolysis may break down the glycosidic bond.

What is a Peptide Bond

A peptide bond is a type of covalent bond formed between two amino acids. Here, the bond is formed between a carbon atom of one amino acid and the nitrogen atom of the other amino acid. The basic structure of an amino acid consists of a central carbon atom attached to a carboxylic group, amino group, hydrogen atom and an alkyl group. One amino acid differs from another amino acid according to this alkyl group.

A condensation reaction occurs between two amino acids. Here, the carboxylic acid of one amino acid reacts with the amine group of another amino acid, releasing a water molecule. The –OH group of the carboxylic acid group forms a water molecule, combining with a hydrogen from amine group.

Figure 03: Formation of a Peptide Bond

The peptide bond is given as –CONH- bond because the bond is formed involving these four atoms as shown in the above image. When two amino acids are bonded to each other through one peptide bond, the final product is a dipeptide; if several amino acids are attached to each other, then it is called oligopeptide. If a high number of amino acids are bonded to each other through peptide bonds, the complex molecule is called a polypeptide.

A peptide bond may undergo hydrolysis. This causes the peptide bond to be broken down, separating the two amino acids. Even though the process is very slow, hydrolysis may occur in the presence of water.

Similarities Between Glycosidic Bond and Peptide Bond

• Both glycosidic bond and peptide bond are types of covalent bonds.
• Both types of bonds are formed through condensation reactions.
• Both types can be cleaved from hydrolysis.
• Both types of bonds may attach two units together.

Difference Between Glycosidic Bond and Peptide Bond

Definition

Glycosidic Bond: Glycosidic bond is a type of covalent bond formed between two monosaccharides.

Peptide Bond: Peptide bond is a type of covalent bond formed between two amino acids.

Occurrence

Glycosidic Bond: Glycosidic bonds are present in carbohydrates/sugars.

Peptide Bond: Peptide bonds are present in proteins.

Chemical Bond

Glycosidic Bond: The glycosidic bond can be given as –C-O-C-.

Peptide Bond: The peptide bond can be given as –CONH-.

Hydrolysis

Glycosidic Bond: The hydrolysis of glycosidic bond forms two monosaccharides.

Peptide Bond: The hydrolysis of peptide bond forms two amino acids.

Conclusion

Both glycosidic bonds and peptide bonds are types of covalent bonds. Glycosidic bonds can be found in carbohydrates. Peptide bonds can be found in proteins. The main difference between glycosidic bond and peptide bond is that a glycosidic bond is formed when two carbon atoms of two different monosaccharides are linked together whereas a peptide bond is formed when a carbon atom of one amino acid is linked to a nitrogen atom of a different amino acid.

References:

 1. “Glycosidic Bond: Definition & Formation.” Study.com. Study.com, n.d. Web. Available here. 08 Aug. 2017.
2. “Peptide bond.” Wikipedia. Wikimedia Foundation, 07 Aug. 2017. Web. Available here. 08 Aug. 2017. 

Image Courtesy:

1. “Figure 03 02 04” By CNX OpenStax –  (CC BY 4.0) via Commons Wikimedia
2. “Glykogen glycosidic bond” By Glykogen.svg: NEUROtikerderivative work: Marek M (talk) – Glykogen.svg (Public Domain) via Commons Wikimedia
3. “224 Peptide Bond-01” By OpenStax College – Anatomy & Physiology, Connexions Web site.  Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia

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