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NCERT Solutions For Class 11 Biology Chapter 9 - Biomolecules
Edited By Irshad Anwar | Updated on May 14, 2025 08:42 AM IST
Chapter 9 of Biology Biomolecules is important for students to understand the complicated concepts of the chapter and study well for their final as well as entrance exams. Biomolecules are required by students as they provide information regarding the chemical compounds upon which life is established, such as carbohydrates, proteins, lipids, and nucleic acids. These molecules play an important role in various biological processes that are essential for growth, development, and 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 help them in exams, but it also lays a strong foundation for further studies.
This Story also Contains
- NCERT Solutions For Class 11 Biology Biomolecules - PDF Download
- Detailed NCERT solutions for Class 11 Biology Chapter 9 on Biomolecules (Solved Exercise)
- Approach to Solve Questions of Class 11 Chapter 9
- Most Important Questions Class 11 Chapter 9
- Chapter Wise NCERT Solutions for Class 11 Biology
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.
NCERT Solutions For Class 11 Biology Biomolecules - PDF Download
Students can download the solutions from below:
Also Read,
- NCERT Notes for class 11 biology chapter 9 biomolecules
- NCERT Exemplar for class 11 biology chapter 9 biomolecules
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
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
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 the pentose sugar is in turn bonded to the hydroxyl group of the 3' carbon of the pentose sugar of the next nucleotide.
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.
Answer:
The structures of 10 small molecular weight biomolecules are as follows
These biomolecules are manufactured in biotechnology industries.
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: 
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.
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.
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.
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:
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.
Answer:
Paper consists of wood pulp, which is predominantly composed of cellulose. Cellulose is a polymer of glucose molecules. Approximately 85 billion tonnes of cellulose are 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 of 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.
Check the NCERT Books and NCERT Syllabus here:
- NCERT Books Class 11 Biology
- NCERT Syllabus Class 11 Biology
- NCERT Books Class 11
- NCERT Syllabus Class 11
Approach to Solve Questions of Class 11 Chapter 9
To answer Biomolecules questions, just follow the simple steps:
- Study the formation of chemicals in living organisms, for example, carbon, hydrogen, and oxygen.
- Study biomacromolecules such as proteins, nucleic acids, and polysaccharides.
- Note down primary and secondary metabolites and their role in metabolism.
- Visit concepts such as the formation of an enzyme, function, and determinants of enzyme activity.
- Practice the detection of bonds such as glycosidic, peptide, and phosphodiester bonds.
- Practice with practice problems to solidify your understanding of biochemical reactions and conversions.
NCERT Solutions for Class 11: Subject-wise
Most Important Questions Class 11 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. Haemoglobin 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 stabilise 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-catalysed, the actual peptide bond formation between amino acids during translation takes place inside the ribosome, a ribonucleoprotein complex. This is catalysed 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-catalysed processes.
What Extra Should Students Study Beyond the NCERT for NEET?
Here is a table for all the important topics from the chapter:
Chapter Wise NCERT Solutions for Class 11 Biology
Below are the chapter-wise solutions:
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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