NCERT Solutions Class 12 Chemistry Chapter 14

NCERT Solutions Class 12 Chemistry Chapter 14 Biomolecules

Chemicals make up life, and living organisms are made up of biomolecules, including carbohydrates, vitamins, lipids, proteins, and nucleic acids. The molecular logic of life processes is made up of these biomolecules interacting with one another. In addition, essential compounds such as vitamins and mineral salts play a vital part in how organisms function. NCERT Solutions Class 12 Chemistry Chapter 14 discusses and answers the structures and functions of some of these biomolecules.

After studying with Extramarks’ Solutions, students will be able to:

  • Comprehend the characteristics of biomolecules such as carbohydrates, proteins, nucleic acids, and hormones and classify carbohydrates, proteins, nucleic acids, and vitamins based on their structures.
  • Differentiate between DNA and RNA.
  • Understand the role of biomolecules in biosystems.

NCERT Solutions Class 12 Chemistry Chapter 14 covers questions and solutions on commonly heard and somewhat unusual biomolecules, such as glycogen, cellulose, saccharides, etc.

These answers are written in primary language to make them easier for students to understand. On Extramarks’ official website, you can get free access to NCERT Solutions Class 12 Chemistry Chapter 14, curated by Extramarks subject experts.

Key Topics Covered in NCERT Solutions Class 12 Chemistry Chapter 14

The concept of a ‘Biomolecule’ is introduced in NCERT Class 12 syllabus. It illustrates how all living things must evolve to survive and reproduce. However, all living organisms are made up of non-living atoms and molecules, and all changes in a living organism occur through a chemical reaction. our solutions provide a detailed understanding of chemical changes inside every being.

The following subtopics are covered in Class 12 Chapter 14 Biomolecules:

  • Carbohydrates
  • Proteins
  • Enzymes
  • Vitamins
  • Nucleic Acid
  • Hormones

‘The role of carbohydrates and proteins in our food’ is an integral part of Biomolecules Class 12 NCERT answers. It refers to all chemical reactions required for living organisms to function.

NCERT Solutions Class 12 Chemistry Chapter 14: Marks Weightage

Name of Chapter Marks allotted
Chapter 14 – Biomolecules 4

NCERT Solutions Class 12 Chemistry Chapter 14: Exercises & Solutions

‘Biomolecules’ teaches that a system grows, sustains, and reproduces itself through a process. Atoms and molecules make up a living system. Biochemistry is the branch of science that studies what happens chemically within a living system. It is necessary to comprehend the living system’s biological and molecular life processes. 

NCERT Chapter 14 Biomolecules is a vital Chapter and thus, needs to be prepared well. The Solutions given below in the links are designed by Extramarks’ academic experts and follow every NCERT guideline. This can also be utilised as reference material when you cannot solve a question from this Chapter. We also have provided some basic examples to showcase our approach to its questions 

NCERT Solutions Class 12 Chemistry Chapter 14 Ex 14.1

NCERT Solutions Class 12 Chemistry Chapter 14 Ex 14.2

NCERT Solutions Class 12 Chemistry Chapter 14 Ex 14.3

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NCERT Solutions Class 12 Chemistry Chapter 14 Ex 14.5

NCERT Solutions Class 12 Chemistry Chapter 14 Ex 14.6

Our subject experts create NCERT Solutions to assist students in understanding concepts correctly, quickly and more efficiently. NCERT Solutions provide comprehensive, step-by-step Solutions to textbook problems. NCERT Solutions, designed by Extramarks, are accessible to all Classes.

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Advantages of NCERT Solutions Class 12 Chemistry Chapter 14

Stated below are some of the advantages students gain from preparing with NCERT Solutions created by Extramarks:

  • It gives you a comprehensive overview of the Chapter.
  • It helps revise because all essential ideas are provided efficiently and are easily understandable.
  • It is a valuable practice paper because it lays out the question format of Board Examinations.
  • Removes any doubts that may have arisen while reading the Chapter.
  • Not only does it help in preparation for Board Examinations, but it aids in preparation for other competitive undergraduate Examinations as well.

All the points mentioned above are important aspects of the Chapter 14 Class 12 Chemistry NCERT Solutions – Biomolecules, and they are mandatory reading for students. It’s an initial step towards learning the fundamentals of more advanced bioChemistry. As a result, students should have a broad understanding of the subject.

NCERT Exemplar Class 12 Chemistry

Students can use the NCERT Class 12 Chemistry Exemplars as assistance to score admirably in their Class 12 Examinations and graduate admission tests. NCERT Exemplar for Class 12 Chemistry includes solved Chapter-by-Chapter questions to help students quickly review the syllabus and perform well in Examinations.

Students get to understand the subject better by practising problems from this guide. Extramarks subject expert team answers all the questions and follows the NCERT syllabus guidelines (2022-2023).

Q.1 What are monosaccharides?


Monosaccharides are carbohydrates that cannot be hydrolysed further to give simpler units of polyhydroxy aldehyde or ketone. Monosaccharides are classified on the bases of number of carbon atoms and the functional group present in them. Monosaccharides containing an aldehyde group are known as aldoses and those containing a keto group are known as ketoses. Monosaccharides are further classified as trioses, tetroses, pentoses, hexoses and heptoses according to the number of carbon atoms they contain. For example, a ketose containing 3 carbon atoms is called ketotriose and an aldose containing 3 carbon atoms is called aldotriose.

Q.2 What are reducing sugars?


Reducing sugars are carbohydrates that reduce Fehling’s solution and Tollen’s reagent. All monosaccharides and disaccharides, excluding sucrose, are reducing sugars.

Q.3 Write two main functions of carbohydrates in plants.


Two main functions of carbohydrates in plants are:

(i) Polysaccharides such as starch serve as storage molecules.

(ii) Cellulose, a polysaccharide, is used to build the cell wall.

Q.4 Classify the following into monosaccharides and disaccharides.

Ribose, 2-deoxyribose, maltose, galactose, fructose and lactose


Monosaccharides: Ribose, 2-deoxyribose, galactose, fructose

Disaccharides: Maltose, lactose

Q.5 What do you understand by the term glycosidic linkage?


Glycosidic linkage refers to the linkage formed between two monosaccharide units through an oxygen atom by the loss of a water molecule.

For example, in a sucrose molecule, two monosaccharide units, ∝-glucose and β- fructose, are joined together by a glycosidic linkage.

Q.6 What is glycogen? How is it different from starch?


Glycogen is a carbohydrate (polysaccharide). In animals, carbohydrates are stored as glycogen.

Starch is a carbohydrate consisting of two components − amylose (15 − 20%) and amylopectin (80 − 85%).

However, glycogen consists of only one component whose structure is similar to amylopectin. Also, glycogen is more branched than amylopectin.

Q.7 What are the hydrolysis products of (i) sucrose and (ii) lactose?


(i) On hydrolysis, sucrose gives one molecule of ∝-D glucose and one molecule of β- D- fructose.

(ii) The hydrolysis of lactose gives β-D-galactose and β-D-glucose.

Q.8 What is the basic structural difference between starch and cellulose?


Starch consists of two components − amylose and amylopectin. Amylose is a long linear chain of ∝−D−(+)−glucose units joined by C1−C4 glycosidic linkage (∝-link).

Amylopectin is a branched-chain polymer of ∝-D-glucose units, in which the chain is formed by C1−C4 glycosidic linkage and the branching occurs by C1−C6 glycosidic linkage.

On the other hand, cellulose is a straight-chain polysaccharide of β-D-glucose units joined by C1−C4 glycosidic linkage (β-link).

Q.9 What happens when D-glucose is treated with the following reagents?
(i) HI (ii) Bromine water (iii) HNO3


(i) When D-glucose is heated with HI for a long time, n-hexane is formed.

(ii) When D-glucose is treated with bromine water, D- gluconic acid is produced.

(iii) On being treated with HNO3, D-glucose get oxidised to give saccharic acid.

Q.10 What are essential and non-essential amino acids? Give two examples of each type.


Essential amino acids are required by the human body, but they cannot be synthesised in the body. They must be taken through food. For example: valine and leucine. Non-essential amino acids are also required by the human body, but they can be synthesised in the body. For example: glycine and alanine

Q.11 Define the following as related to proteins

(i) Peptide linkage (ii) Primary structure (iii) Denaturation.


(i) Peptide linkage: The amide formed between −COOH group of one molecule of an amino acid and −NH2 group of another molecule of the amino acid by the elimination of a water molecule is called a peptide linkage.

(ii) Primary structure: The primary structure of protein refers to the specific sequence in which various amino acids are present in it, i.e., the sequence of linkages between amino acids in a polypeptide chain. The sequence in which amino acids are arranged is different in each protein. A change in the sequence creates a different protein.

(iii) Denaturation: In a biological system, a protein is found to have a unique three-dimensional structure and a unique biological activity. In such a situation, the protein is called native protein. However, when the native protein is subjected to physical changes such as change in temperature or chemical changes such as change in pH, its H-bonds are disturbed. This disturbance unfolds the globules and uncoils the helix. As a result, the protein loses its biological activity. This loss of biological activity by the protein is called denaturation. During denaturation, the secondary and the tertiary structures of the protein get destroyed, but the primary structure remains unaltered. One of the examples of denaturation of proteins is the coagulation of egg white when an egg is boiled.

Q.12 What are the common types of secondary structure of proteins?


There are two common types of secondary structure of proteins:

(i) ∝-helix structure: In this structure, the −NH− group of an amino acid residue forms H-bond with the group of the adjacent turn of the right-handed screw (∝-helix).

(ii) β-pleated sheet structure: This structure is called so because it looks like the pleated folds of drapery. In this structure, all the peptide chains are stretched out to nearly the maximum extension and then laid side by side.These peptide chains are held together by intermolecular hydrogen bonds.

Q.13 What type of bonding helps in stabilising the ∝-helix structure of proteins?


The H-bonds formed between the −NH group of each amino acid residue and thegroup of the adjacent turns of the ∝-helix helps in stabilising the helix.

Q.14 Differentiate between globular and fibrous proteins.


S. No. Globular protein Fibrous protein
(i) The polypeptide chain in this protein is folded around itself, giving rise to a spherical structure. It is a fibre-like structure formed by the polypeptide chain. These proteins are held together by strong hydrogen and disulphide bonds.
(ii) It is usually soluble in water. It is usually insoluble in water.
(iii) All enzymes are globular proteins. Some hormones such as insulin are also globular proteins. Fibrous proteins are usually used for structural purposes. For example, keratin is present in nails and hair; collagenin tendons; and myosin in muscles.

Q.15 How do you explain the amphoteric behaviour of amino acids?


In aqueous solution, the carboxyl group of an amino acid can lose a proton and the amino group can accept a proton to give a dipolar ion known as zwitter ion.

Therefore, in zwitter ionic form, the amino acid can act both as an acid and as a base.

Thus, amino acids show amphoteric behaviour.

Q.16 What are enzymes?


Enzymes are proteins that catalyse biological reactions. They are very specific in nature and catalyse only a particular reaction for a particular substrate. Enzymes are usually named after the particular substrate or the class of substrate upon which they work.

For example, the enzyme used to catalyse the hydrolysis of maltose into glucose is named as maltase.

C 12 H 22 O 11 Maltase 2 C 6 H 12 O 6 MathType@MTEF@5@5@+=feaaguart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbwvMCKfMBHbqedmvETj2BSbqefm0B1jxALjhiov2DaerbuLwBLnhiov2DGi1BTfMBaebbnrfifHhDYfgasaacH8IrFz0xbbf9q8WrFfeuY=Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0=yr0RYxir=Jbba9q8aq0=yq=He9q8qqQ8frFve9Fve9Ff0dmeaabaqaaiaacaGaaeaabaWaaqaafaaakeaadaWfqaqaaiaadoeadaWgaaWcbaGaaGymaiaaikdaaeqaaOGaamisamaaBaaaleaacaaIYaGaaGOmaaqabaGccaWGpbWaaSbaaSqaaiaaigdacaaIXaaabeaaaeaaaeqaaOWaa4ajaSqaaiaab2eacaqGHbGaaeiBaiaabshacaqGHbGaae4CaiaabwgaaeqakiaawkziamaaxababaGaaGOmaiaadoeadaWgaaWcbaGaaGOnaaqabaGccaWGibWaaSbaaSqaaiaaigdacaaIYaaabeaakiaad+eadaWgaaWcbaGaaGOnaaqabaaabaaabeaaaaa@4F3F@

Maltose Glucose

Sometimes, the enzymes are also named after a particular reaction. For example, the enzymes used to catalyse the oxidation of one substrate with the simultaneous reduction of another substrate are named as oxidoreductase enzymes.The name of an enzyme ends with ‘− ase’.

Q.17 What is the effect of denaturation on the structure of proteins?


As a result of denaturation, globules get unfolded and helix get uncoiled. Secondary and tertiary structures of protein are destroyed, but the primary structures remain unaltered. It can be said that during denaturation, secondary and tertiary-structured proteins get converted into primary-structured proteins. Also, as the secondary and tertiary structures of a protein are destroyed, the protein loses its biological activity.

Q.18 How are vitamins classified? Name the vitamin responsible for the coagulation of blood.


On the basis of their solubility in water or fat, vitamins are classified into two groups:

(i) Fat-soluble vitamins: Vitamins that are soluble in fat and oils, but not in water, belong to this group. For example: Vitamins A, D, E, and K

(ii) Water-soluble vitamins: Vitamins that are soluble in water belong to this group. For example: B group vitamins (B1, B2, B6, B12, etc.) and vitamin C.

Vitamin K is responsible for the coagulation of blood.

Q.19 Why are vitamin A and vitamin C essential to us? Give their important sources.


The deficiency of vitamin A leads to xerophthalmia (hardening of the cornea of the eye) and night blindness. The deficiency of vitamin C leads to scurvy (bleeding gums). Thus, vitamin A and vitamin C are essential to us. The sources of vitamin A are fish liver oil, carrots, butter, and milk. The sources of vitamin C are citrus fruits, amla, and green leafy vegetables.

Q.20 What are nucleic acids? Mention their two important functions.


Nucleic acids are biomolecules found in the nuclei of all living cells, as one of the constituents of chromosomes. There are mainly two types of nucleic acids that are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are also known as polynucleotides as they are long-chain polymers of nucleotides.

Two main functions of nucleic acids are as follows:

(i) DNA is responsible for the transmission of inherent characters from one generation to the next. This process of transmission is called heredity.

(ii) Nucleic acids (both DNA and RNA) are responsible for protein synthesis in a cell. Even though the proteins are actually synthesised by the various RNA molecules in a cell, the message for the synthesis of a particular protein is present in DNA.

Q.21 What is the difference between a nucleoside and a nucleotide?


A nucleoside is formed by the attachment of a base to 1′ position of sugar.

Nucleoside = Sugar + Base

On the other hand, all the three basic components of nucleic acids (i.e., pentose sugar, phosphoric acid, and base) are present in a nucleotide.

Nucleotide = Sugar + Base + Phosphoric acid

Q.22 The two strands in DNA are not identical but are complementary. Explain.


In the helical structure of DNA, the two strands are held together by hydrogen bonds between specific pairs of bases. Cytosine forms hydrogen bond with guanine, while adenine forms hydrogen bond with thymine. As a result, the two strands are complementary to each other.

Q.23 Write the important structural and functional differences between DNA and RNA.


The structural differences between DNA and RNA are as follows:

(i) The sugar moiety in DNA molecules is β-D-2 deoxyribose. The sugar moiety in RNA molecules is β-D-ribose.
(ii) DNA contains thymine (T). It does not contain uracil (U). RNA contains uracil (U). It does not contain thymine (T).
(iii) The helical structure of DNA is double-stranded. The helical structure of RNA is single-stranded.

The functional differences between DNA and RNA are as follows:

(i) DNA is the chemical basis of heredity. RNA is not responsible for heredity.
(ii) DNA molecule do not synthesise proteins, but transfer coded message for the synthesis of proteins in the cells. Proteins are synthesised by RNA molecules in the cells.

Q.24 What are the different types of RNA found in the cell?


The three types of RNA found in the cell are as follows:

(i) Messenger RNA (m-RNA)

(ii) Ribosomal RNA (r-RNA)

(iii) Transfer RNA (t-RNA)

Q.25 Enumerate the reactions of D-glucose which cannot be explained by its open chain structure.


(1) Aldehydes give Schiff’s test and react with NaHSO3 to form the hydrogen sulphite addition product. However, glucose does not undergo these reactions.

(2) The pentaacetate of glucose does not react with hydroxylamine. This indicates that a free −CHO group is absent from glucose.

(3) Glucose exists in two crystalline forms ∝ and β. The ∝-form (m.p. = 419 K) crystallises from a concentrated solution of glucose at 303 K and the β-form (m.p = 423K) crystallises from a hot and saturated aqueous solution at 371 K. This behavior cannot be explained by the open chain structure of glucose.

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FAQs (Frequently Asked Questions)

1. How can I prepare for Chapter 14 of Chemistry Class 12?

It is necessary to read the Chapter to comprehend what it offers fully. While reading the chapter, students should quickly note all the significant points to access them during the Examination. To answer any question from this Chapter, students should regularly practice the numerous names, formulae, and functions. Aside from that, students must consult Extramarks Chapter 14 Class 12 Chemistry NCERT Solutions and complete all the included activities.

2. What are some of the characteristics of glucose?

  1. Glucose has the following properties:
  • Pentaacetate is produced when glucose is acetylated with acetic anhydride, confirming the presence of hydroxyl groups in glucose.
  • When glucose reacts with hydroxylamine, it produces monoxime, which combines with a molecule of hydrogen cyanide to form cyanohydrin. This proves that glucose has a carbonyl group.
  • Glucose is oxidised to gluconic acid when it reacts with weak oxidising agents like bromine water. On the other hand, when nitric acid is oxidised, saccharic acid is generated.

3. Explain the difference between glycogen and starch, as discussed in NCERT Solutions Class 12 Chemistry Chapter 14.

Carbohydrates are stored in the form of glycogen, a polysaccharide in animals. Similarly, amylose and amylopectin are the two components of starch. Even though starch and glycogen are carbohydrates, glycogen only has an element. When opposed to amylopectin, glycogen has a more branched structure. Class 12 students can better comprehend these concepts by studying the NCERT Solutions created by Extramarks experts.

4. What are monosaccharides, and what do they do?

  1. Monosaccharides are carbohydrate molecules that cannot be further broken down (hydrolysed) into ketones or units of polyhydroxy aldehyde. The functional group and number of carbon atoms in these monosaccharides can be used to Classify them further.


  • Functional Groups-Based Classification:

The monosaccharides that contain a keto-group are Classified as ketoses, whereas those containing aldehyde groups are called aldoses.


  • Classification Based on the Number of Carbon Atoms:

Monosaccharides are Classified as trioses, pentoses, tetroses, or heptoses based on the number of carbon atoms present.

The monosaccharides are named after the two classes mentioned above. For example, aldotetrose is an aldose with four carbon atoms, while ketotetrose is a ketose with four carbon atoms.

5. What are biomolecules and their types described in NCERT Solutions Class 12 Chemistry Chapter 14?

  1. Biomolecules are organic compounds that have a role in various metabolic activities such as cell repair, digestion, and growth. These biomolecules support all of the living activities required for human survival. 

Biomolecules are divided into four categories: 

  • Lipids
  • Proteins
  • Nucleic acids
  • Carbohydrates. 

Besides  these, a slew of biomolecules plays a role in metabolic processes.

6. Can students rely on Extramarks for NCERT Solutions Class 12 Chemistry Chapter 14?

Students can use Extramarks’ NCERT Solutions Class 12 Chemistry Chapter 14 to help them with their homework, prepare for Examinations, and prepare any competitive Examinations. These solutions are created by subject matter specialists using the most recent NCERT Syllabus and its recommendations. Every solution includes structures and chemical equations to assist students in grasping the subject quickly. Students will be able to review the crucial principles in this Chapter by going through the solutions curated by Extramarks.