Peptide Bonds and Other Bonds in Biomolecules

Before we proceed with peptide linkage definition and different kinds of bonds that exist in biomolecules, let us take a look at a few relevant concepts.  

All living organisms have biomolecules that are primarily constituted of polymers. Polymerisation is the formation resulting from multiple monomers. Monomers are the smaller units that are held together by various kinds of bonds. 

The formation of these bonds is dependent on the monomer's chemical nature. It is these different kinds of bonds that are discussed. 

Peptide Bond

If you are considering what is peptide linkage, it is another term for a peptide bond. When two molecules form a chemical bond in which the carboxyl group of one molecule undergoes reaction with the amino acid of another molecule, a peptide bond is formed. 

Peptide bond formation steps are also called a dehydration synthesis reaction where one molecule of water is released in the process. As in the case of proteins, peptides are also made up of amino acids that are linked amongst itself in a chain-like formation. 

Did You Know?

Nucleic acids are essentially such molecules that engage in coding genetic information of organisms. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two types of nucleic acids that are instrumental in reproduction, repair and protein synthesis. RNA and DNA are the polymers that are made up of monomers known as nucleotides.

Glycosidic Bond 

The covalent bond which joins a carbohydrate with another molecule or group is called a glycosidic bond. The constituting element of this bond is a glycoside. For instance, within adenosine molecule, adenine and ribose are connected by an N-glycosidic bond. 

Glycosidic bonds are of two types – 1, 4 beta and 1, 4 alpha glycosidic bonds. When water reacts with glycosidic bonds, it hydrolyses forming two monosaccharides. 

Phosphodiester Bond 

The covalent bonds which join 5 carbon of one deoxyribose with that of 3 carbon of the next deoxyribose of the adjacent nucleotide, within phosphate groups, are called phosphodiester bonds. 

It is one of the most critical components for structuring DNA and RNA to maintain genetic code integrity. The phosphodiester bond helps in linking phosphate molecules to sugar molecules. 

Base Pairing in DNA 

Base pair in DNA primarily relates to the bonding of two chemical bases with the formation of “rung of the DNA ladder”. There are two strands in the molecule that twist around each other, and the strands are made up of phosphate groups and alternating sugar or deoxyribose. The base pairing in DNA imparts its helical structure and allows replication. 

Test Your Knowledge 

i. Which of the following joins amino acids?

(a) Glycosidic bond    

(b) Ionic bond 

(c) Hydrogen bond  

(d) Peptide bond   

ii. Which of the following constitute a dipeptide?

(a) 2 amino acids and 3 peptide bonds 

(b) 2 amino acids and 1 peptide bond 

(c) 2 amino acids and 4 peptide bonds  

(d) 2 amino acids and 2 peptide bonds 

Solutions: i. (d) Peptide bond, ii. (b) 2 amino acids and 1 peptide bond 

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FAQ (Frequently Asked Questions)

1. What is the nature of bond linking monomers in a polymer?

Peptide bonds link monomers in a polymer. It is formed out of dehydration, that is, the amino group and carboxyl group of two different amino acids react to give rise to peptide bonds.

2. What type of linkage is present in nucleic acid?

Nucleic acid consists of phosphodiester linkages. The phosphodiester linkage joins the nucleotides which are further composed of a phosphate group, 5-carbon sugar, and a nitrogenous base.

3. What is peptide linkage?

The chemical bond within two molecules that are formed with a reaction between carboxyl groups of one molecule with an amino group of another molecule define peptide linkage. The reaction releases one molecule of water in the process.