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Peptide bond and other bonds in biomolecules can be classified in two parts, such as:
- Glycosidic bond
- Phosphodiester bond
Non-living molecules and atoms create the living system. Biomolecules or biological molecules are products that are created by living organisms and cells. Proteins, lipids, nucleic acid, carbohydrates, etc are the different types of biomolecules.
Biomolecules play an important role in maintaining the life process where simple molecules like mineral salts and vitamins act in the efficient functioning of the organism.
There are different kind of bonds in biomolecules that holds together the monomers. The chemical nature of the monomers affects the formation of the bonds.
| Table of Content |
Key Terms: Polymers, Monomers, Biomolecules, Bonds, Linkage, DNA, Molecules, Group, Atoms, Water, Amino acid, Proteins, Peptide bond, Carboxyl group, Dehydration synthesis
Peptide bond
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A Peptide bond or peptide linkage is the bond that holds together the proteins or polymers of the amino acid.
- It creates a chain-like formation when peptides are formed with amino acids.
- To represent chemically, the peptide bond formation creates a connection between the –NH2 group and the –COOH group.
- A peptide bond is formed when the carboxyl group of one molecule is reacted with the amino acid of another molecule.
The steps of peptide bond formation are also known as the dehydration synthesis reaction as a single molecule of water is released in the process.
Peptide Bond Structure
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Glycosidic Bond
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Glucosidic bonds are the covalent bonds that create a linkage between a carbohydrate and another molecule or group. Glycoside is the main element of this bond.
- 1,4 beta and 1,4 alpha glucoside bonds are the two types of glycosidic bond.
- Two monosaccharides are formed when there is a reaction between water and glycosidic bonds and it hydrolyses.
- The loss of a water molecule results in the oxide linkage which links two monosaccharides.
- Such a linkage which is supported by an oxygen atom is known as glycosidic linkage.
Glucosidic Bond
Phosphodiester Bond
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Phosphodiester bond is a covalent bond that creates a link between 5 carbon of one deoxyribose and 3 carbon of the next deoxyribose of the immediate nucleotide, within the phosphate group.
- In order to maintain integrity within the generic code, this bond plays an important role in organizing RNA and DNA.
- Sugar molecules are linked to phosphate molecules through the phosphodiester bond.
Phosphodiester bond
Base Pairing in DNA
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The bonding of two chemical bases is known as base pairing.
- In a molecule, two strands twist around each other.
- One is made of a phosphate group and the other is made up of alternating sugar or deoxyribose.
- The helical structure of the DNA is because of its base pairing.
- Base pairing also helps in replication.
Base Pairing in DNA
Things to Remember
- Biomolecules are made up of polymers.
- Many monomers together result in the formation of polymers.
- A peptide bond definition (also called amide bond) is formed between the α-nitrogen atom of an amino acid and carbonyl carbon of the second.
- A glycosidic bond connects a large number of monosaccharide units which together are known as polysaccharides or disaccharides.
- Peptide bond joins amino acids and is broken by hydrolysis.
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Previous Year Questions
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Sample Questions
Ques. Is sucrose a non-reducing sugar? (1 mark)
Ans: Yes, sucrose is a non-reducing sugar. The formation of a glycosidic bond involves the reducing groups of fructose and glucose. Thus, sucrose is a non-reducing sugar.
Ques. What are the characteristics of peptide bonds? (3 marks)
Ans. The characteristics of peptide bonds are:
- Peptide bonds are strong because of their partial double bond character.
- They are unbreakable by the high salt concentration or heating
- They can be broken by certain enzymes or through exposure to strong acids or bases for a long time.
- Peptide groups contain partial positive and negative charged groups.
Ques. What are the different forms of peptide bonds? (2 marks)
Ans. There are several forms of peptide bonds. They are:
- Dipeptide
- Tripeptide
- Tetrapeptide
- Oligopeptide
- Polypeptide
- Macropeptide
Ques. How a glycosidic bond does leads to the formation of polysaccharides? (1 mark)
Ans. A glycosidic bond is a reaction between two units of sugar. It is the reaction between the H- group of one sugar and the –OH group of another sugar. It releases the water and joins the units of sugar together. This results in the formation of polysaccharides.
Ques. Which reaction results in the formation of glycosidic and peptide bonds? (1 mark)
Ans. The removal of a water molecule leads to the formation of two types of covalent bonds such as glycosidic and peptide bonds. This process is known as dehydration or condensation reaction which results in the formation of covalent bonds.
Ques. Name some substances that contain glycosidic and peptide bonds. (1 mark)
Ans. The substance which contains peptide bonds is insulin which is a protein molecule. The substance which contains glycosidic bonds is inulin which is a polysaccharide molecule.
Ques. What is the structure of the peptide bond? (3 marks)
Ans. The peptide bond has a balanced, trans, and inflexible configuration. It also partially exhibits the characteristic of the double bond.
The coplanarity feature of a peptide bond expresses the incomplete sharing of the two pairs of electrons between the carboxyl oxygen and amide nitrogen.
The peptide bond consists of atoms such as C, H, N, and O which are placed in the same plane which is similar to the arrangement of the hydrogen atom of the amide group and the oxygen atom of the carboxyl group.
Ques. What are the elements of biomolecules? (2 marks)
Ans. The large molecules which are made out of smaller organic molecules to engage in life processes are known as macromolecules.
There are four major macromolecules – carbohydrates, lipids, proteins, and nucleic acid. Each of the elements has a major contribution to the wide range of life functioning.
Ques. Give some examples of a phosphodiester bond. (2 marks)
Ans. The nucleotides in RNA and DNA are attached with the help of a phosphodiester bond. NADP and NDP are dinucleotides that involve phosphodiester bonds. The individual nucleotides of polynucleotide also have phosphodiester bonds.
Ques. What is the difference between Primary Bonds and Secondary Bonds in biological molecules? (4 marks)
Ans. The differences between Primary and Secondary Bonds in biological molecules are:
| Primary Bond | Secondary Bond |
|---|---|
| Primary bonding is known to take place when electrons are lost or gained so that the outer shell is filled. | Secondary bonds are not bonds that has a valence electron shared or donated. These bonds are formed when an uneven charge distribution takes place, forming a dipole. |
| Formed between atoms due to sharing of electrons. | Formed when atoms or groups of atoms are brought together. |
| These are permanent covalent bonds. | These are temporary forces of attraction. |
| Examples: Glycosidic Bond, an Ester Bond, Peptide Bond. | Examples: Disulphide Bond, Hydrogen Bond, Hydrophobic Interaction, Etc. |
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