[Biology Class Notes] on Peptide Bonds Biomolecules Pdf for Exam

Peptide Bond Formation Steps

Nucleic acids, carbohydrates, proteins and different significant biomolecules are called macromolecules collectively. These macromolecules contain polymers with monomers linked by way of certain bonds. Thus, what is peptide linkage? 

Define Peptide Linkage

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This image depicts the structure of peptide bonds. 

There is no clear peptide linkage definition. You should understand that proteins contain polypeptides since they are the polymers of different amino acids. It is the amino acids that are linked by the peptide bonds. There are a couple of functional groups within the amino acid category, and they are carboxylic acid or the –COOH group and amine or –NH-2 group. Peptide bonds are usually amide bonds (-CONH) between the -COOH group and the –NH₂ group of the contiguous amino acids. With the formation of a peptide bond, there is the elimination of a water molecule.

Peptide Bond Definition Biology

A couple of amino acids formed a covalent bond between them, which is called a peptide bond. Different living organisms make use of peptide bonds for building long-chain amino acids, called proteins. Now when it comes to an understanding of the vital role played by proteins in the lives of human beings, they are needed for almost everything. Proteins make way for structural support and even prove to be effective in catalyzing some of the most important reactions. Proteins also help in determining molecules across the environment. Therefore, a peptide bond forms the basis of different biological reactions. Peptide bond formation is one of the most important requirements of life.

Peptide Bond Formation Steps

At the molecular stage, dehydration reaction leads to the peptide bonds. Two amino acids tend to bond when oxygen and two hydrogens are eliminated from molecules. To this reaction, the carboxyl group is given by them whereas a hydroxyl group is destroyed. Amino groups that come from different amino acids lose hydrogen. Next, nitrogen plays the role of a substitute for the hydroxyl group, and thus a peptide bond is formed. It is only because of this reason that peptide bonds are also referred to as the substituted amide linkages. During the peptide bond formation, the amino acids used are called residues after the reaction because they lose several atoms and are covalently bonded to one another post the formation of a peptide bond.

Here, it is important to note that the nitrogen to carbon bond formed in the peptide bond is entirely different from the nitrogen-carbon bonds present in the various other molecule parts. Oxygen on carboxyl bond side has a negative charge while nitrogen has a positive charge. Both the negative and the positive charges are slight, and it is this interaction that results in the nitrogen and the carbon sharing more electors in comparison to what they share. The whole procedure leads to the establishment of an electronic dipole.

The number of extra electrons has the bond serving in the form of a double bond that is quite rigid and is not able to rotate. The unit consisting of a total of 6 molecules is called a peptide group appearing in the form of a flat plane or ball. Carbons found in the middle of the amino acids have a total of 4 equal bonds along with the ability to rotate freely. Hence, when several amino acids bond together, a chain of unbending atom planes is moulded around the peptide bond. The flexible bonds of carbon duly connect this bond. It is this whole setting that consents peptide chains to crook and rotates, resulting in highly advanced creations with the ability to catalyse reactions.

Nature of Bond Linking Monomers in a Polymer

Polymers like nucleic acids, polysaccharides and proteins are formed especially when the monomers link in long chains. There are different varieties of bonds providing stability and structure to biomolecules while making them functional at the same time. When a particular amino acid’s carboxyl group reacts with an amino group of another amino acid, proteins form. It is dehydration that results in the formation of a peptide bond.

The formation of polysaccharides takes place when multiple mono-saccharides get linked in once place through a glycosidic bond. Even in this procedure, dehydration plays a vital role in bond formation. Glycosidic bonds connect with the carbohydrates or carbohydrate molecules.

The formation of nucleic acid takes place when a phosphate group, pentose sugar and nitrogenous base link and form the polynucleotide chain.    

Nucleic Acid has What Type of Linkage?

There are three types of linkages available in nucleic acid. They are phosphodiester linkage joining the nucleic acid monomeric unit, glycosidic linkage joining base and ribose sugar and hydrogen linkage joining the nitrogen bases.