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NCERT Solutions For Class 11 Biology Chapter 9 Biomolecules

NCERT Solutions For Class 11 Biology Chapter 9 Biomolecules

Edited By Irshad Anwar | Updated on Apr 14, 2025 03:25 PM IST

NCERT Solutions for Class 11 Biology Chapter 9 Biomolecules are made for students to learn the complex ideas of the chapter and prepare well for their final as well as entrance exams. Biomolecules are necessary for students because they give information about the chemical compounds on which life is based, namely carbohydrates, proteins, lipids, and nucleic acids. These molecules have an important role in numerous biological processes that are required for growth, development, as well as metabolism. With NCERT Solutions, students can improve their knowledge, determine and rectify weak points, and consolidate their basic knowledge in biology. Not only does it make them trained in exams, but it also lays a strong foundation for further studies.

This Story also Contains
  1. NCERT Solutions For Class 11 Biology Biomolecules - PDF Download
  2. Detailed NCERT solutions for Class 11 Biology Chapter 9 on Biomolecules (Solved Exercise)
  3. How to solve NCERT Chapter 9 questions effectively?
  4. Overview of NCERT Class 11 Chapter 9
  5. Practice Questions from Chapter 9
  6. Chapter Wise NCERT Solutions for Class 11 Biology
NCERT Solutions For Class 11 Biology Chapter 9 Biomolecules
NCERT Solutions For Class 11 Biology Chapter 9 Biomolecules

If it is difficult for you to understand the concept of biomolecules, you are on the right platform. The NCERT Solutions for Class 11 are written in a simple and easy-to-read manner to make students skilled in core concepts and score well in exams. The questions and their detailed answers in the chapter are prepared by subject matter experts in sync with the updated CBSE syllabus.

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NCERT Solutions For Class 11 Biology Biomolecules - PDF Download

Students can download the solutions from below:

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Detailed NCERT solutions for Class 11 Biology Chapter 9 on Biomolecules (Solved Exercise)

The complete solved exercise is given below:

Q1. What are macromolecules? Give examples.

Answer:

The complex high molecular weight molecules separated in acid-insoluble fractions in the assistance of trichloroacetic acid are referred to as macromolecules. They are polymers of a molecular weight of 10,000 daltons and above. Proteins, carbohydrates, nucleic acids etc., are macromolecules. There are lipids in the acid-insoluble fraction too, but they are not of high molecular weight.

Q2. Illustrate a glycosidic, peptide and a phospho-diester bond.

Answer:

Glycosidic bond- This bond is formed between the 1st carbon atom of one monosaccharide and 4 carbon atoms of a neighbouring monosaccharide unit. During the formation of this bond, a water molecule is released. A representation of a glycosidic bond is as follows

Glycosidic Bond


Peptide bond- This is a covalent bond formed between the carboxyl group of one amino acid and the amino group of neighbouring amino acids. A water molecule is released in the formation of a peptide bond. A representation of a peptide bond is as follows

Peptide Bond

Phosphodiester bond- It refers to the phosphate-hydroxyl linkage between two nucleotides. In this bond, the phosphate attached to the hydroxyl group at the 5' carbon of pentose sugar is in turn bonded to the hydroxyl group of the 3' carbon of the pentose sugar of the next nucleotide.

 Phosphodiester bond


3. What is meant by the tertiary structure of proteins?

Answer:

The three-dimensional configuration of a protein that arises from repeated coiling and folding of helical and pleated polypeptide chains is termed its tertiary structure. Through repeated folding and coiling, polar side chains remain exposed whereas non-polar amino acids are kept inside. The tertiary structure is bonded through weak bonds. The activity of a protein exists in tertiary structures.


Q4. Find and write down structures of 10 interesting small molecular weight biomolecules. Find if there is any industry which manufactures the compounds by isolation. Find out who are the buyers.

Answer:

The structures of 10 small molecular weight biomolecules are as follows

1650612083293


10 small molecular weight biomolecules


These biomolecules are manufactured in biotechnology industries.

6. Find out and make a list of proteins used as therapeutic agents. Find other applications of proteins (e.g., Cosmetics etc.)

Answer:

Proteins with therapeutic uses are insulin, oxytocin, ADH, thrombin, fibrinogen, renin, immunoglobulin, diastase, streptokinase etc.

Other applications of proteins are

1. As cosmetics- Protein such as casein is used in beauty creams, shampoos etc.

2. Sweeteners- Thaumatin and monellin are sweet proteins.

3. Dietary supplements- Proteins can be used as dietary supplements.

Q7. Explain the composition of triglyceride.

Answer: triglyceride

A triglyceride is a chemical formed by the esterification of three molecules of fatty acids with one molecule of trihydric alcohol called glycerol. All three fatty acids of triglyceride can be similar as in tripalmitin or dissimilar as in palmito-oleoistearin, dipalmitostearin, etc.

three molecules of fatty acids


Q8. Can you describe what happens when milk is converted into curd or yoghurt, from your understanding of proteins?

Answer:

Milk has a protein known as casein. When we mix a little curd into milk, the protein casein is coagulated by the action of lactic acid bacteria and thus milk is transformed into curd. Coagulation breaks the structure of the protein casein.

Q9. Can you attempt building models of biomolecules using commercially available atomic models (Ball and Stick models).

Answer:

Yes, we can try constructing models of biomolecules with the help of commercially purchased atomic models like ball and stick models. The stick is, in the model, taken to be a bond and balls of varying colours are taken to be atoms.

Q10. Attempt titrating an amino acid against a weak base and discover the number of dissociating ( ionizable ) functional groups in the amino acid.

Answer:

When we titrate an amino acid against a weak base, it dissociates into its functional groups i.e. -COOH (carboxylic group) and -NH (amino group)

Q11. Draw the structure of the amino acid, alanine.

Answer:

The structure of the amino acid alanine is represented below:

structure of the amino acid alanine

Q13. Find out a qualitative test for proteins, fats and oils, and amino acids and test any fruit juice, saliva, sweat and urine for them.

Answer:

One of the qualitative tests for proteins is the xanthoproteic test. When a qualitative test for protein in urine is done using the aid of the xanthoproteic test, if a yellow precipitate is formed, then it is guaranteed that there is protein in it. The qualitative test for fats is the emulsification test.

During the emulsification test, the experimental material is first treated with ethanol and then dissolved in water. The development of emulsion proves the existence of fats. The qualitative analysis for oils is the paper test. The material to be tested is placed on paper. The presence of oil is established when oil marks remain. The qualitative analysis for amino acids is the ninhydrin test.

Q14. Find out how much cellulose is made by all the plants in the biosphere and compare it with how much of paper is manufactured by man and hence what the consumption of plant material by man annually. What a loss of vegetation!

Answer:

Paper consists of wood pulp which is predominantly composed of cellulose. Cellulose is a polymer of glucose molecules combined. Approximately 85 billion tonnes of cellulose is generated every year in the biosphere. Paper production requires 0.5 billion tonnes of wood. The rise in the usage of wood has caused immense loss in vegetation.

Q15. Describe the important properties of enzymes.

Answer:

Enzymes are proteinaceous substances which are capable of catalysing chemical reactions of biological origin without themselves undergoing any change. They are commonly called biocatalysts. The properties of enzymes are as follows:

1. Enzymes are proteins by nature

2. Optimum temperature- An enzyme is active within a narrow range of temperature. The temperature at which an enzyme is most active is called the optimum temperature. The enzyme activity decreased above and below this temperature.

3. Optimum pH- Every enzyme has an optimum pH at which it is maximum active. Most of the intracellular enzymes work at neutral pH.

4. Enzymes are substrate specific, i.e. one enzyme catalyses only a particular substrate. Every enzyme has specific sites called active sites for the binding of substrate.

5. Only a small quantity ofthe enzyme is capable of forming the desired product

6. Enzyme activity is sensitive to certain chemicals called inhibitors or modulators.

How to solve NCERT Chapter 9 questions effectively?

To answer Biomolecules questions, just follow the simple steps:

  1. Study the formation of chemicals in living organisms, for example, carbon, hydrogen, and oxygen.
  2. Study biomacromolecules such as proteins, nucleic acids, and polysaccharides.
  3. Note down primary and secondary metabolites and their role in metabolism.
  4. Visit concepts such as the formation of an enzyme, function, and determinants of enzyme activity.
  5. Practice the detection of bonds such as glycosidic, peptide, and phosphodiester bonds.
  6. Practice with practice problems to solidify your understanding of biochemical reactions and conversions.
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Check the NCERT Books and NCERT Syllabus here:

Overview of NCERT Class 11 Chapter 9

Biomolecules falls under Unit 3 – Cell: Structure and Functions in the new syllabus of CBSE 11th standard Biology. According to old question papers, this unit has a maximum of 15 marks, which is around 21% of the total exam weightage. It is important to understand the concepts of subtopics in this chapter to obtain good marks.

If you are confused while reading Biomolecules, re-read the chapter, attempt questions yourself, and then match your responses with trusted solutions. This will not only benefit you in the school exams but also augment your preparation for competitive exams such as NEET.

NCERT Solutions for Class 11: Subject-wise

Importance of Biomolecules Class 11 Biology

Here are some key reasons why biomolecules are important:

Importance

Explanation

Building Blocks of Life

Biomolecules such as proteins, carbohydrates, lipids, and nucleic acids form the structural and functional basis of living organisms.

Energy Storage and Supply

Carbohydrates and lipids provide the energy required for various biological activities.

Genetic Information Transfer

Nucleic acids (DNA and RNA) store and transmit genetic information for growth and reproduction.

Metabolic Functions

Enzymes, which are proteins, regulate biochemical reactions essential for life processes.

Practice Questions from Chapter 9

Some questions from Biomolecules are given below:

1. Which of the following is a homopolymer?

a. Cellulose

b. Hemoglobin

c. DNA

d. RNA

Answer: a. Cellulose

Explanation: A homopolymer is a polymer consisting of one kind of monomer. Cellulose is a polysaccharide containing only glucose units and hence a homopolymer. Hemoglobin is a protein (heteropolymer), and DNA and RNA are nucleic acids that consist of varying nucleotides.

2. What type of bond joins monosaccharides in polysaccharides?

a. Peptide bond

b. Glycosidic bond

c. Phosphodiester bond

d. Hydrogen bond

Answer: b. Glycosidic bond

Explanation: Glycosidic bonds are the chemical connections between monosaccharide units in polysaccharides. Peptide bonds connect amino acids in proteins, phosphodiester bonds connect nucleotides in DNA and RNA, and hydrogen bonds are weaker interactions that stabilize the structure of molecules.

3. Which of the following is the simplest amino acid?

a. Alanine

b. Tyrosine

c. Glycine

d. Asparagine

Answer: c. Glycine

Explanation: Glycine is the simplest amino acid because it possesses the smallest side chain, which consists of a single hydrogen atom. Glycine is thus exceptional among the 20 common amino acids.

4. Proteins are heteropolymers made up of how many types of monomers?

a. 20 types

b. 40 types

c. 30 types

d. Only one type

Answer: a. 20 types

Explanation: Proteins are heteropolymers since they consist of varied kinds of monomers, that is, amino acids. Proteins have 20 conventional amino acids that form the building units of proteins.

5. Which reaction is not enzyme-mediated in biological processes?

a. Glycolysis

b. Protein synthesis

c. DNA replication

d. Formation of peptide bonds in ribosomes

Answer: d. Formation of peptide bonds in ribosomes

Explanation: Although the overall process of protein synthesis is enzyme-catalyzed, the actual peptide bond formation between amino acids during translation takes place inside the ribosome, a ribonucleoprotein complex. This is catalyzed by ribozymes (catalytic RNA) contained within the ribosome, not by free enzymes. Enzymes do play a role in other processes of protein synthesis. Glycolysis, protein synthesis (overall process), and DNA replication are all enzyme-catalyzed processes.

Chapter Wise NCERT Solutions for Class 11 Biology

Below mentioned are the Chapterwise solutions:

NCERT Class 11 Biology Chapter 9, "Biomolecules," describes the structure and functions of key biomolecules in easy and simple words. The chapter discusses vital concepts such as the kinds of biomolecules (carbohydrates, proteins, lipids, and nucleic acids), their functions in the body, enzyme activities, and metabolism. These solutions are by the CBSE syllabus and can be helpful for school examinations and enhancing the concepts of key points. The solutions are clearly and concisely written so that they are perfect for swift revision when exam time is around the corner. Overall, the solutions are top-notch study materials for studying biomolecules and excelling at exams.

Frequently Asked Questions (FAQs)

1. What are the benefits of biomolecules class 11 ncert solutions?

The benefits of Chapter 9 of NCERT Solutions for Class 11 Biology are:

  • NCERT is the base of your learning.  
  • NCERT solutions for class 11 biology chapter 9 biomolecules will also help you with competitive exams like NEET.  
  • You will get all the answers to biomolecules ncert biology and biomolecules class 11 pdf will help you to score good marks in the exam. 
  • Biomolecules pdf class 11  will also help you in your 12th board exam.  
  • Biomolecules class 11 pdf will also boost your knowledge. 
  • To score well in the examination, follow the NCERT syllabus and solve the exercise given in the NCERT Book. To practice more problems, students must refer to NCERT Exemplar.
2. What are the different types of structures of biomacromolecules given biomolecules ncert biology?

The different types of structures of biomacromolecules given in Chapter 9 of NCERT Solutions for Class 11 Biology are: 

  • primary  
  • secondary  
  • tertiary and  
  • quaternary 
3. What are the important topics of ch 9 bio class 11?

The important topics of NCERT Solutions for Class 11 Biology Chapter 9 are: 

  • Primary and Secondary Metabolites  
  • Biomacromolecules  
  • Proteins  
  • Polysaccharides  
  • Nucleic Acids  
  • Structure of Proteins  
  • Nature of Bond Linking Monomers in a Polymer  
  • Dynamic State of Body Constituents - Concept of Metabolism  
  • Metabolic Basis for Living  
  • The Living State  
  • Enzymes 
4. List the characteristics of the enzymes discussed in Chapter 9 of the NCERT Solutions for Class 11 Biology.

The properties of enzymes covered in Chapter 9 of NCERT Solutions for Class 11 Biology are: 

  • The enzymes are complex macromolecules with a higher molecular weight.
  • The enzymes help break down larger molecules into simpler molecules by catalyzing the biochemical reactions occurring within the cell.
  • Enzymes can only speed up a reaction.
  • Enzymes have an impact on the biochemical reaction's rate, but they have no impact on the reaction's direction.
  • Enzymes are action specific.
  • At a pH level between 6 and 8, enzyme activity peaks.
5. What is the importance of biomolecules in biology?

Biomolecules are fundamental to life as they constitute cell structural elements, store and transmit genetic information and catalyze biochemical processes. They encompass carbohydrates, lipids, proteins, and nucleic acids with each having a particular function within cellular processes. Their interactions modulate metabolism, growth, and reproduction in every living organism.

6. How are proteins formed according to NCERT?

Proteins are synthesized through the polymerization of amino acids with peptide bonds, as stated by NCERT. A peptide bond is established between the carboxyl (-COOH) group of a particular amino acid and the amino (-NH₂) group of another, losing a water molecule (condensation reaction). The amino acid sequence (primary structure) decides the function of the protein. Additional folding and interactions result in secondary, tertiary, and quaternary structures to give functional proteins.

7. What is the structure and function of nucleic acids in Class 11?

Nucleic acids (DNA and RNA) are nucleotide polymers, composed of a sugar, phosphate group, and nitrogenous base (A, T/U, G, C). DNA is double-helix, whereas RNA is typically single-stranded. They carry and transfer genetic information, with DNA coordinating protein synthesis and RNA helping in transcription and translation. Their structure allows replication, gene expression, and heredity in living things.

8. How do enzymes work as biological catalysts?

Enzymes function as biological catalysts by accelerating biochemical reactions without being used up. They reduce the activation energy by binding to substrates at their active site, creating an enzyme-substrate complex. This binding allows for the breaking or formation of bonds, transforming substrates to products with efficiency. Enzymes are very specific in their function, are active within a particular temperature and pH, and control metabolic pathways in living organisms.

9. What is the role of vitamins in biomolecules?

Vitamins serve as coenzymes or coenzyme precursors, facilitating enzymatic reactions during metabolism. Vitamins assist in energy production, immune function, cell growth, and repair. Although they do not contribute to energy, their lack can result in disease and metabolic disorders. Vitamins are either water-soluble (B-complex, C) or fat-soluble (A, D, E, K), with each having a unique biochemical function.


10. What are the characteristics of biomolecules?

Biomolecules possess the following features:

  • Organic in Nature – Contains primarily carbon, hydrogen, oxygen, and nitrogen.
  • Macromolecular or Micromolecular – Found in the form of small molecules (e.g., vitamins) or large polymers (e.g., proteins, nucleic acids).
  • Specific Structure and Function – Every biomolecule possesses a distinctive structure that dictates its biological function.
  • Involved in Metabolism – Take part in biochemical reactions necessary for life.
  • Intermolecular Interactions – Engage in hydrogen bonding, ionic bonds, and hydrophobic interactions to develop complex structures.

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A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

Option 1)

0.34\; J

Option 2)

0.16\; J

Option 3)

1.00\; J

Option 4)

0.67\; J

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times.  Assume that the potential energy lost each time he lowers the mass is dissipated.  How much fat will he use up considering the work done only when the weight is lifted up ?  Fat supplies 3.8×107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate.  Take g = 9.8 ms−2 :

Option 1)

2.45×10−3 kg

Option 2)

 6.45×10−3 kg

Option 3)

 9.89×10−3 kg

Option 4)

12.89×10−3 kg

 

An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

Option 1)

2,000 \; J - 5,000\; J

Option 2)

200 \, \, J - 500 \, \, J

Option 3)

2\times 10^{5}J-3\times 10^{5}J

Option 4)

20,000 \, \, J - 50,000 \, \, J

A particle is projected at 600   to the horizontal with a kinetic energy K. The kinetic energy at the highest point

Option 1)

K/2\,

Option 2)

\; K\;

Option 3)

zero\;

Option 4)

K/4

In the reaction,

2Al_{(s)}+6HCL_{(aq)}\rightarrow 2Al^{3+}\, _{(aq)}+6Cl^{-}\, _{(aq)}+3H_{2(g)}

Option 1)

11.2\, L\, H_{2(g)}  at STP  is produced for every mole HCL_{(aq)}  consumed

Option 2)

6L\, HCl_{(aq)}  is consumed for ever 3L\, H_{2(g)}      produced

Option 3)

33.6 L\, H_{2(g)} is produced regardless of temperature and pressure for every mole Al that reacts

Option 4)

67.2\, L\, H_{2(g)} at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, Mg_{3}(PO_{4})_{2} will contain 0.25 mole of oxygen atoms?

Option 1)

0.02

Option 2)

3.125 × 10-2

Option 3)

1.25 × 10-2

Option 4)

2.5 × 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

Option 1)

decrease twice

Option 2)

increase two fold

Option 3)

remain unchanged

Option 4)

be a function of the molecular mass of the substance.

With increase of temperature, which of these changes?

Option 1)

Molality

Option 2)

Weight fraction of solute

Option 3)

Fraction of solute present in water

Option 4)

Mole fraction.

Number of atoms in 558.5 gram Fe (at. wt.of Fe = 55.85 g mol-1) is

Option 1)

twice that in 60 g carbon

Option 2)

6.023 × 1022

Option 3)

half that in 8 g He

Option 4)

558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

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