NCERT Solutions for Class 11 Biology Chapter 9 - Biomolecules

NCERT Solutions for Class 11 Biology Chapter 9 Biomolecules are important concepts in understanding the chemical composition of matter found in living entities. This chapter is categorised under the latest CBSE Syllabus 2023-24. Students who look forward to making a career in the medical field must know the fundamentals. NCERT Solutions for Class 11 include solved solutions for all the questions appearing in the textbook, answered in the same order for the convenience of students.

Students might be tense before their examinations. But with a deep understanding of concepts, thorough revision and practice, students are assured of performing exceedingly well. Class 11 can be a crucial year, as a substantial number of questions appear in the competitive exams; therefore, analysing and understanding concepts is inevitable. NCERT Solutions steps in right here, sufficing all the academic needs of students.

NCERT Solutions for Class 11 Biology Chapter 9 – Biomolecules

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Access Answers to NCERT Class 11 Biology Chapter 9 – Biomolecules

1. What are macromolecules? Give examples.

Solution:

Macromolecules are the biomolecules that are formed by the polymerisation of a huge number of micromolecules possessing higher molecular weight. Micromolecules are found in the colloidal state in the intercellular fluid due to their insoluble nature. Protein is a macromolecule.

2. Illustrate a glycosidic peptide and a phospho-diester bond.

Solution:

Glycosidic bond – The bond between the individual monosaccharides is called a glycosidic linkage. This bond is formed between two carbon atoms of two adjacent monosaccharide units.

Peptide bond – It is a covalent bond. The amino acids in proteins are linked to one another through peptide bonds. It is formed when the carboxyl group (-COOH) of one amino acid interacts with the amino group (-NH2 ) of the adjacent amino acid when condensed.

Formation of Peptide bond – Example

Phospho-diester bond – That joins successive sugar molecules in a polynucleotide. It is a strong covalent bond formed between two adjacent sugar groups and phosphate. These are the bonds that form the sugar-phosphate backbone of the nucleic acids.

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

Solution:

It is a structure that forms when the secondary coiled polypeptides are folded to produce a hollow, wollen ball-like structure. It is folded such that the functional side groups appear on the surface while the inactive side groups are found inside.

4. 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.

Solution:

5. Proteins have a primary structure. If you are given a method to know which amino acid is at either of the two termini (ends) of a protein, can you connect this information to the purity or homogeneity of a protein?

Solution:

The positional information of a protein is called the primary structure of the protein. The first amino acid in a protein is called the N-terminal amino acid, and the last amino acid in a protein is called the C-terminal amino acid.

Yes, we can connect this information to check the purity or homogeneity of a protein. On the basis of carboxyl and amino groups, amino acids can be acidic, basic and neutral. Proteins can be acidic, basic and neutral.

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

Solution:

Following is the list of proteins used as therapeutic agents.

Insulin, Oxytocin, Immunoglobin, Antidiuretic Hormone( ADH), Thrombin, Fibrinogen, Renin and streptokinases.

Some other applications are

• They are used as artificial sweeteners. Thaumatin is a low-calorie sweetener.
• Proteins are used as dietary supplements to maintain health.
• They are used in creams and shampoos.

7. Explain the composition of triglyceride.

Solution:

When glycerol combines with three fatty acids on each of the OH groups through ester bonds, it is known as a triglyceride.

All three fatty acids of triglyceride in pure fat are similar, while in mixed fat, they are dissimilar.

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

Solution:

During fermentation, milk protein such as casein is denatured, which transforms globular proteins into fibrous proteins. This change is responsible for the production of curd or yoghurt.

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

Solution:

Yes, Biomolecules can be represented by the ball and stick model. Here, the bonds which hold the molecule are indicated by sticks, while the atoms are represented by balls. The figure below is a model of D-glucose, where atoms of hydrogen are indicated by green balls, oxygen atoms are represented by pink balls, and carbon atoms are represented by grey balls.

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

Solution:

The pH of the amino acid is recorded, and the weak base is slowly supplemented to the amino acids while continuously noting the pH. The number of changes recorded indicates the number of ionisable functional groups –COOH in the acidic range and –NH₂ in the alkaline range.

11. Draw the structure of the amino acid alanine.

Solution:

The structure of Alanine is as follows:

12. What are gums made of? Is Fevicol different?

Solution:

Gums are heteropolysaccharides formed by different monosaccharide units associated with glycosidic bonds. On the other hand, Fevicol is different from gums, as it is made up of synthetic polymers.

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

Solution:

Qualitative test for proteins

Biuret test: Biuret test identifies the presence of proteins by turning the colour of the solution from light blue to purple.

Qualitative test for fats and oils

Grease test for oils: Certain oils give a translucent stain on blue paper. This test can be used to detect the presence of oils and fats.

Qualitative test for amino acids

Ninhydrin test

Upon adding ninhydrin reagent to the solution, the colour of the solution turns to pink, purple or blue based on the type of amino acid.

14. 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 is the consumption of plant material by man annually. What a loss of vegetation!

Solution:

The biosphere produces about 100 billion tonnes of cellulose out of 170 billion tonnes of total organic matter. Production of paper consumes about 0.5 billion tonnes of wood. Trees are also utilised for other purposes, including food, medicines, timber, spices, etc. An approximate estimate of 1.5 billion tonnes of food is required. Wood requirement for various purposes includes 2 billion tonnes. Therefore, it is difficult to gauge the annual consumption of plant material by man. Thus, the use of cellulose led to a great loss of vegetation.

15. Describe the important properties of enzymes.

Solution:

Almost all enzymes are proteins. Important properties of enzymes are as follows:

• They have a higher molecular weight and are complex macromolecules.
• They catalyse the biochemical reactions involved in the cell, assisting in breaking down larger molecules into simpler molecules or getting together two smaller molecules to form a larger one.
• Enzymes do not initiate but accelerate a reaction.
• They affect the rate of biochemical reaction and do not influence the direction of the reaction.
• They are action-specific.
• A higher turnover of enzymes causes an increase in the efficiency of a reaction. Most of the enzymes have a high turnover number.
• Enzymes are affected by temperature. As the temperature increases, enzymatic activity decreases. Maximum activity is observed at 30-40 degree Celsius.

• Maximum activity is observed at a 6-8 pH level.
• With an increase in substrate concentration, the enzymatic velocity also increases, reaching maximum velocity.

NCERT Solutions for Class 11 Biology Chapter 9 – Biomolecules

NCERT Solutions for Class 11 Biology Chapter 9 – Biomolecules are categorised under Unit 3 – Cell: Structure and Functions of the latest CBSE Syllabus 2023-24. This particular unit totals up to 15 marks as per the previous years’ question papers which approximately adds up to 21% of the total weightage of the paper.

Students can revise from previous years’ question papers to get an idea of the typology of questions that can be expected from this chapter. Apart from learning concepts, knowing how to answer is the key to scoring optimum marks, and NCERT Solutions help students with it.

List of subtopics covered in Chapter 9 – Biomolecules

NCERT Solutions for Class 11 Biology Chapter 9 – Biomolecules

Biomolecules include some important topics which enable students to understand the chemical composition. To be able to analyse a living tissue sample and identify a specific organic compound in higher classes, a fundamental understanding of different types of tissues, anatomy, morphology, the common site at which they are found, different functionalities they carry out, etc., are equally required to comprehend concepts.

Students thus understand different chemical reactions and their conversions, the role of enzymes, the nature of different enzyme actions, various factors affecting the activity of enzymes, and the classification and nomenclature of different enzymes.

Key Features of NCERT Solutions for Class 11 Biology Chapter 9 – Biomolecules

• Solutions framed by subject-matter experts.
• Solutions are provided as per the expected answering pattern.
• NCERT Solutions are available for free download.
• Simple and easy to understand.
• Efficient and effective study tool.

Disclaimer – 

Dropped Topics – 

9.8 Nature of Bond Linking Monomers in a Polymer
9.9 Dynamic State of Body Constituents – Concept of Metabolism
9.10 Metabolic Basis for Living
9.11 The Living State
Question nos 2, 3, 5, 8, 10