CBSE Class 12 Chemistry Chapter 14 Biomolecules NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 12 PDF

This chapter delves into the essential molecules of life, covering carbohydrates, proteins, enzymes, nucleic acids, and vitamins. The NCERT Solutions for Class 12 Chemistry Chapter 14: Biomolecules provide detailed explanations and step-by-step solutions for various questions, including Multiple Choice Questions (MCQs). These solutions clarify concepts like glycosidic linkages in polysaccharides, the structure and function of proteins, the mechanism of enzyme action, and the building blocks of DNA and RNA. Understanding these topics is crucial for students preparing for their board examinations, as they form the basis of many biological processes. The provided solutions aim to enhance conceptual clarity and aid in effective exam revision.

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Quick info

Board	CBSE
Class	Class 12
Subject	Chemistry Exemplar
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 14

Chapter summary

Chapter 14, Biomolecules, focuses on the chemistry of life. This NCERT Solutions set covers key concepts such as the classification and structure of carbohydrates (monosaccharides, disaccharides, polysaccharides), proteins (amino acids, peptide bonds, primary, secondary, tertiary structures), enzymes, nucleic acids (DNA, RNA), and vitamins. The solutions address multiple-choice questions, helping students understand the relationships between different biomolecules and their biological significance.

Learning outcomes

Understand the structure and function of carbohydrates like glycogen and sucrose.
Differentiate between various types of polysaccharides and their storage forms.
Identify the products of disaccharide hydrolysis.
Define and identify anomers in carbohydrate chemistry.
Recognize the structural similarities between glycogen and amylopectin.

Topics covered

Paper topics

Biomolecules
Carbohydrates
Polysaccharides
Glycogen
Amylopectin
Disaccharides
Sucrose
Hydrolysis
Anomers
α-D glucose
β-D glucose
Animal Starch

Important topics

Structure and storage of Glycogen
Hydrolysis of Sucrose
Definition and identification of Anomers
Comparison of Glycogen and Amylopectin structures
Role of α-D glucose and β-D glucose

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Questions and Solutions

Question 1

Glycogen is a branched chain polymer of <math>\alpha</math>-D glucose units in which the main chain is formed by C1—C4 glycosidic linkage, whereas branching occurs by the formation of C1—C6 glycosidic linkage. The structure of glycogen is similar to which of the following?

amylose
amylopectin
cellulose
glucose

Solution: Glycogen is a polysaccharide composed of numerous α-D-glucose units linked together. The primary chain of glycogen is formed by α-(1→4) glycosidic linkages. Additionally, glycogen contains branches, which are formed by α-(1→6) glycosidic linkages. This branched structure, with both linear chains and frequent branching points, is very similar to the structure of amylopectin, another polysaccharide found in plants. Amylose, in contrast, is a linear chain of glucose units linked by α-(1→4) glycosidic bonds without branching. Cellulose is also a linear polysaccharide but is composed of β-D-glucose units linked by β-(1→4) glycosidic bonds.

Therefore, the structure of glycogen is most similar to amylopectin.

Answer: (b) amylopectin

Question 2

Which of the following polymers is stored in the liver of animals?

Amylose
Cellulose
Amylopectin
Glycogen

Solution: Glycogen is the primary storage form of glucose in animals, analogous to starch in plants. It is predominantly stored in the liver and muscles. Liver glycogen helps maintain blood glucose levels, while muscle glycogen serves as an energy reserve for muscle activity. Glycogen is a highly branched polymer of α-D-glucose. Amylose and amylopectin are components of starch, found in plants. Cellulose is a structural polysaccharide in plants.

Answer: (d) Glycogen

Question 3

Sucrose (cane sugar) is a disaccharide. One molecule of sucrose on hydrolysis gives .........

2 molecules of glucose
2 molecules of glucose + 1 molecule of fructose
1 molecule of glucose + 1 molecule of fructose
2 molecules of fructose

Solution: Sucrose is a non-reducing disaccharide formed from the glycosidic linkage between the anomeric carbon (C-1) of α-D-glucose and the anomeric carbon (C-2) of β-D-fructose. Upon hydrolysis, this glycosidic bond is broken. The hydrolysis reaction can be represented as:

$C_{12}H_{22}O_{11} + H_2O \xrightarrow{H^+} C_6H_{12}O_6 (\text{glucose}) + C_6H_{12}O_6 (\text{fructose})$

Thus, one molecule of sucrose yields one molecule of D-glucose and one molecule of D-fructose. This mixture is also known as invert sugar because sucrose is dextrorotatory, but the resulting mixture of glucose and fructose is levorotatory.

Answer: (c) 1 molecule of glucose + 1 molecule of fructose

Question 4

Which of the following pairs represents anomers?

(The image displays structures of cyclic carbohydrates. The question asks to identify the pair that are anomers.)

Solution: Anomers are stereoisomers of cyclic saccharides that differ in configuration at the carbon atom that was the carbonyl carbon in the open-chain form. This carbon is called the anomeric carbon. In the case of glucose, which is an aldose, the anomeric carbon is C-1. The α-anomer has the hydroxyl group (-OH) attached to the anomeric carbon pointing down (or to the right in a Fischer projection), while the β-anomer has the -OH group pointing up (or to the left).

The provided options (represented by figures in the source) show different configurations at the anomeric carbon. The pair that differs only in the configuration at C-1 are the anomers. Specifically, if the -OH group at C-1 is on the right side (in a Fischer projection context for cyclic forms), it's the α-form, and if it's on the left side, it's the β-form. The figures in option (c) show two cyclic structures that differ only in the orientation of the hydroxyl group at the anomeric carbon (C-1), making them anomers.

Answer: (c)

Common mistakes

Confusing the structures and linkages of different polysaccharides (e.g., glycogen, amylopectin, cellulose).
Incorrectly identifying the products of disaccharide hydrolysis.
Misunderstanding the definition and identification of anomers.

Revision tips

Focus on the specific glycosidic linkages (C1-C4, C1-C6) mentioned for glycogen.
Review the hydrolysis products of common disaccharides like sucrose.
Pay close attention to the definition and visual representation of anomers.
Compare the structures of similar biomolecules like glycogen and amylopectin.

Practice MCQs

Q1. Glycogen, a branched chain polymer of α-D glucose units, forms its chain through C1-C4 glycosidic linkages and branching through C1-C6 glycosidic linkages. Which other polysaccharide shares a similar structure?

Q2. Which polysaccharide is primarily stored in the liver of animals?

Q3. Hydrolysis of one molecule of sucrose, a disaccharide, yields:

Q4. What defines a pair of anomers in carbohydrate chemistry?

Frequently asked questions

What are biomolecules?

Biomolecules are organic molecules that are essential for life, forming the structural and functional components of living organisms. Examples include carbohydrates, proteins, lipids, nucleic acids, and vitamins.

What is the difference between glycogen and amylopectin?

Both glycogen and amylopectin are branched polysaccharides of glucose. Glycogen is primarily found in animals and stored in the liver and muscles, while amylopectin is a component of starch found in plants. Their structures are very similar, with both having C1-C4 glycosidic linkages in the main chain and C1-C6 linkages for branching.

What happens when sucrose is hydrolyzed?

When sucrose (a disaccharide) is hydrolyzed, it breaks down into one molecule of glucose and one molecule of fructose. This process is typically catalyzed by an acid or an enzyme like invertase.

What are anomers in the context of carbohydrates?

Anomers are a specific type of stereoisomer of cyclic monosaccharides that differ in configuration at the anomeric carbon (C-1 in aldoses and ketoses). For example, α-D-glucose and β-D-glucose are anomers.

Why is glycogen called 'animal starch'?

Glycogen is called 'animal starch' because it serves as the primary storage form of glucose in animals, similar to how starch serves as the storage form of glucose in plants.

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