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CBSE Class 12 Chemistry Notes Chapter 14 Biomolecules

Jasmine Grover

Content Strategy Manager

Biomolecules are important organic molecules that fuse together to form complex organic compounds and govern the metabolism of living organisms. Proteins, carbohydrates, nucleic acids, enzymes and lipids form the living system of biomolecules .

• Carbohydrates are essential polyhydroxy aldehydes or ketones , forming the building blocks of energy in living organisms. 
• They encompass monosaccharides, disaccharides, and polysaccharides, with glucose being a vital energy source derived from starch digestion. 
• Proteins are composed of amino acids linked by peptide bonds. 
• Denaturation of proteins, disrupting protein structure, occurs with changes in pH or temperature. 
• Enzymes , primarily proteins, accelerate biochemical reactions with specificity. 
• Vitamins are crucial for health and are classified into fat-soluble (A, D, E, K) and water-soluble (B, C) types. 
• Nucleic acids , polymers of nucleotides, store genetic information as DNA and RNA. 
• DNA, with deoxyribose sugar, encodes hereditary data, while RNA, containing ribose, aids in protein synthesis via mRNA, rRNA, and tRNA.

According to the CBSE Class 12 Chemistry Syllabus 2023-24, this chapter has been renumbered as Chapter 10. Biomolecules Class 12 Notes are important for revision as the chapter holds a weightage of 7 marks in the Class 12 Chemistry examination 2024.

Biomolecules Notes

Carbohydrates

• Carbohydrates are organic compounds primarily produced by plants.
• Examples include cane sugar, glucose, and starch.
• They are characterized by a general formula, Cx(H 2 O)y, but not all compounds fitting this formula are classified as carbohydrates.
• Carbohydrates are defined as optically active polyhydroxy aldehydes or ketones , or compounds that produce such units upon hydrolysis .

Classification of Carbohydrates

Carbohydrates are classified into three groups based on their behavior on hydrolysis.

Monosaccharides

Monosaccharides cannot be further hydrolyzed to simpler units. Examples include glucose, fructose, and ribose. 

• Monosaccharides are classified into aldoses and ketoses based on their functional groups and the number of carbon atoms they contain.
• Glucose is obtained from sucrose through hydrolysis with dilute acids or from starch via hydrolysis with dilute sulfuric acid under pressure and elevated temperature.
• Its structure comprises six carbon atoms arranged in a straight chain, featuring functional groups such as aldehyde and hydroxyl. 
• Glucose, an aldohexose, is also known as dextrose and exists as the monomer of larger carbohydrates like starch and cellulose. 
• It forms two cyclic hemiacetal structures (a and b forms) known as anomers, with the configuration determined by the hydroxyl group at C1.
• The cyclic structure is depicted using the Haworth projection, representing the pyranose structure.

• Fructose, a ketohexose, is derived from sucrose hydrolysis and is naturally present in fruits, honey, and vegetables, serving as a natural sweetener.
• With the molecular formula C 6 H 12 O 6 , fructose contains a ketonic functional group at carbon number 2 and belongs to the D-series, exhibiting laevorotatory properties.
• Fructose exists in both open-chain and cyclic forms, with the cyclic form forming a five-membered ring called furanose upon the addition of a hydroxyl group at C5.

Disaccharides

• Disaccharides form via glycosidic linkage between two monosaccharide units, resulting from the loss of water.
• Sucrose yields invert sugar upon hydrolysis and exhibits laevorotatory properties.
• Maltose comprises two glucose units linked by a glycosidic linkage between C1 and C4.
• Lactose, found in milk, consists of galactose and glucose units linked between C1 and C4, and is a reducing sugar .

Polysaccharides

• Polysaccharides , composed of multiple monosaccharide units, function as vital food storage and structural materials in living organisms.
• Starch, a primary plant storage polysaccharide, contains amylose and amylopectin.
• Amylose is water-soluble and unbranched, while amylopectin is insoluble and branched.
• Cellulose , predominant in plant cell walls, comprises straight chains of β-D-glucose units linked by glycosidic bonds between C1 and C4.
• Glycogen , akin to animal starch, is stored in the liver, muscles, and brain, characterized by high branching and serving as a glucose reserve.

Importance of carbohydrates

• Carbohydrates provide a significant portion of the diet of plants and animals, serving as vital energy sources.
• Starch in plants and glycogen in animals function as storage forms of carbohydrates, offering easily accessible energy reserves.
• Cellulose constitutes the cell walls of bacteria and plants, with industrial applications including wood and cotton fiber products.
• Carbohydrates are crucial raw materials in industries like textiles, paper, lacquers, and breweries.
• Aldopentoses like D-ribose and 2-deoxy-D-ribose are key components of nucleic acids, underscoring their importance in biological systems.
• Proteins are abundant biomolecules in living organisms, vital for biological processes.
• Classification of proteins is done based on the shape, constituents and nature of molecules.
• Composed of α-amino acids, proteins are sourced from foods like milk, cheese, pulses, peanuts, fish, and meat.
• They contribute to growth, maintenance, and bodily functions.

Amino Acids

• Amino acids contain amino (–NH 2 ) and carboxyl (–COOH) functional groups. 
• They are categorized as acidic, basic, or neutral depending on the relative number of amino and carboxyl groups in their molecule. 
• Essential amino acids must be obtained through diet, while non-essential amino acids can be synthesized in the body.

Structure of proteins

Proteins are composed of amino acids linked by peptide bonds , formed by the condensation of amino and carboxyl groups. 

• Dipeptides, tripeptides, and polypeptides result from the combination of amino acids, with proteins containing more than a hundred amino acid residues.
• Proteins are classified into fibrous and globular types based on their molecular shape. 
• Fibrous proteins have parallel polypeptide chains held by hydrogen and disulfide bonds, while globular proteins have coiled polypeptide chains, giving them a spherical shape. 
• Primary (amino acid sequence)
• Secondary (a-helix, b-pleated sheet)
• Tertiary (overall folding)
• Quaternary (spatial arrangement of subunits).

Structure of Proteins

Denaturation of Proteins

• Proteins in biological systems with unique three-dimensional structures and biological activity are termed native proteins.
• Denaturation occurs when native proteins undergo physical or chemical changes such as temperature fluctuations or pH alterations.
• It disrupts hydrogen bonds, causing globules to unfold and helices to uncoil, resulting in the loss of the protein's biological activity.
• During denaturation, secondary and tertiary protein structures are destroyed, while the primary structure remains intact.
• Common examples include the coagulation of egg white upon boiling and the curdling of milk due to lactic acid formation by bacteria.
• Enzymes facilitate chemical reactions vital for life, such as food digestion and energy production.
• It acts as biocatalysts and are mostly globular proteins, enabling reactions to occur under mild conditions in the body.
• The compounds are highly specific for particular reactions and substrates, often named after the compounds they act upon or the reactions they catalyze.
• It reduces the activation energy required for reactions, similar to chemical catalysts, allowing reactions to proceed efficiently.
• Enzymes typically end with "-ase" and may be named based on the reaction they catalyze or the substrate they act upon. 
• For instance, maltase catalyzes the hydrolysis of maltose to glucose.

• Vitamins are essential organic compounds required in small amounts in the diet to maintain optimum growth and health.
• Most of these compounds cannot be synthesized in the human body but are abundant in various foods. 
• Plants can synthesize most vitamins.
• They are classified into fat-soluble (A, D, E, K) and water-soluble (B complex, C) groups based on their solubility properties.
• While these compounds are essential, excess intake can be harmful. 

Types of vitamins

Nucleic acids

• Nucleic acids are polymers of nucleotides, comprising a-pentose sugar, phosphoric acid , and nitrogen-containing bases.
• In the nucleus of living cells, characteristics are transmitted via chromosomes , composed of proteins and nucleic acids.
• DNA and RNA are the two main types of nucleic acids.
• They are responsible for the transmission of characteristics from one generation to another.
• Nucleotides are joined by phosphodiester linkages between the 5' and 3' carbon atoms of the pentose sugar.
• DNA forms a double-stranded helix held together by hydrogen bonds between specific base pairs.
• RNA , categorized into messenger RNA (m-RNA), ribosomal RNA (r-RNA), and transfer RNA (t-RNA), plays distinct roles in protein synthesis.
• DNA serves as the repository of genetic information and is responsible for species identity maintenance.

Nucleic Acid

• Hormones , produced by endocrine glands , act as intracellular messengers in the body.
• They include steroids (e.g., estrogens, androgens), polypeptides (e.g., insulin, endorphins), and amino acid derivatives (e.g., epinephrine, norepinephrine).
• Peptide and steroid hormones are two types of hormones.
• They maintain biological balance, such as insulin regulating blood glucose levels, and glucagon increasing glucose levels.
• Thyroxine, produced by the thyroid gland , regulates metabolism, with abnormal levels leading to conditions like hypothyroidism or hyperthyroidism.
• Steroid hormones from adrenal cortex and gonads (testes, ovaries) regulate various body functions, such as carbohydrate metabolism and secondary sex characteristics.
• An imbalance in hormone levels can lead to disorders like Addison's disease (adrenal cortex dysfunction) or menstrual irregularities.

There are Some important  List Of Top Chemistry Questions On Biomolecules Asked In CBSE CLASS XII

CBSE CLASS XII Related Questions

1. define the term solution. how many types of solutions are formed write briefly about each type with an example., 2. which of the following compounds would undergo aldol condensation, which the cannizzaro reaction and which neither write the structures of the expected products of aldol condensation and cannizzaro reaction.  \((i) methanal \) \((ii) 2-methylpentanal \) \((iii) benzaldehyde \) \((iv) benzophenone \) \((v) cyclohexanone \) \((vi) 1-phenylpropanone \) \((vii) phenylacetaldehyde \) \((viii) butan-1-ol \) \((ix) 2, 2-dimethylbutanal\), 3. indicate the steps in the preparation of:   k 2 cr 2 o 7 from chromite ore.   kmno 4 from pyrolusite ore., 4. draw the structures of optical isomers of:  (i)  \([cr(c_2o_4)_3]^{3–}\) (ii)  \([ptcl_2(en)_2]^{2+}\) (iii)  \([cr(nh_3)2cl_2(en)]^{+}\), 5. write the nernst equation and emf of the following cells at 298 k :  (i) mg(s) | mg 2+ (0.001m) || cu 2+ (0.0001 m) | cu(s)  (ii) fe(s) | fe 2+ (0.001m) || h + (1m)|h 2 (g)(1bar) | pt(s)  (iii) sn(s) | sn 2+ (0.050 m) || h + (0.020 m) | h 2 (g) (1 bar) | pt(s)  (iv) pt(s) | br 2 (l) | br -  (0.010 m) || h + (0.030 m) | h 2 (g) (1 bar) | pt(s)., 6. in the button cells widely used in watches and other devices the following reaction takes place: zn(s) + ag 2 o(s) + h 2 o(l)  \(\rightarrow\)  zn 2+ (aq) + 2ag(s) + 2oh -  (aq)  determine  \(\triangle _rg^\ominus\)  and  \(e^\ominus\)  for the reaction., similar chemistry concepts.

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Biomolecules Class 12 Notes and Mind map

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Welcome to our comprehensive guide on Biomolecules for Class 12 students. Whether you're studying for your CBSE exams or simply looking to deepen your understanding of this fascinating subject, you're in the right place. In this article, we have compiled detailed class notes, mind maps, and scoring questions to help you master the concepts of Biomolecules. Biomolecules are the building blocks of life, playing critical roles in the functioning of living organisms.

From carbohydrates to lipids, proteins, and nucleic acids, each biomolecule has its own unique structure and function. Understanding these molecules is essential for grasping fundamental concepts in biology, biochemistry, and genetics. Our notes provide a clear and concise overview of each biomolecule, highlighting their structures, properties, and important functions.

The mind maps offer a visual representation of the interconnections between biomolecules, aiding in memory retention and concept mapping. Lastly, our scoring questions are designed to test and reinforce your understanding, allowing you to assess your knowledge and identify areas for improvement. So, dive in and explore our Biomolecules Class 12 Notes, Mind map, and Scoring Questions to ace your exams and enhance your knowledge of this fascinating subject.

Class 12 Chemistry Chapter 10, dedicated to Biomolecules, offers an extensive exploration into the fascinating world of biological molecules that are crucial for life processes. This chapter is a key part of the Class 12 curriculum, providing students with vital insights into the structure, function, and importance of biomolecules. The Class 12 Chemistry Biomolecules notes encompass comprehensive details about various biomolecules such as carbohydrates, proteins, nucleic acids, and vitamins, essential for students in their academic journey in chemistry.

For Class 12th students, understanding biomolecules is not just important for exams but also for a foundational knowledge in biochemistry, which has applications in fields like medicine, nutrition, and biotechnology. The biomolecules class 12 chemistry notes are crafted to cover every aspect of the topic, including the classification of biomolecules, their physical and chemical properties, and their roles in biological systems.

These notes also include biomolecules class 12th MCQs, which are crucial for students preparing for competitive exams as well as their board exams. The biomolecules class 12 chemistry important questions focus on key areas that are often emphasized in exams, helping students to solidify their understanding and prepare effectively.

For a more visual approach to learning, the biomolecules class 12 mind map provides a quick and efficient way to review the entire chapter, making it easier for students to recall important information during their exams. Additionally, the biomolecules class 12 chemistry notes PDF offers a convenient way for students to access study materials anytime, enhancing their learning experience.

In conclusion, the Chapter 10 of Class 12 Chemistry is a comprehensive guide for understanding biomolecules. With detailed notes, mind maps, MCQs, and important questions, students can effectively prepare for their exams and gain a thorough understanding of this vital topic in the field of chemistry.

Classification of Biomolecules

Biomolecules in living organisms are classified into several major categories based on their structure and function. These include carbohydrates, lipids, proteins, nucleic acids, and enzymes. Each class of biomolecules plays a crucial role in the structure and functioning of cells and organisms.

Carbohydrates

Carbohydrates are organic compounds made up of carbon, hydrogen, and oxygen, often following the formula (CH₂O)n. They are classified into monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Carbohydrates serve as the primary source of energy and as structural components in organisms.

Lipids are a diverse group of hydrophobic molecules, including fats, oils, waxes, phospholipids, and steroids. They are essential for storing energy, forming cell membranes, and acting as signaling molecules.

Proteins are large biomolecules made of amino acids linked by peptide bonds. They are crucial for various functions such as catalysis of biochemical reactions, structural support, transport, communication, and immune response.

Nucleic Acids

Nucleic acids, namely DNA and RNA, are the molecules responsible for storing and transmitting genetic information. DNA serves as the blueprint for protein synthesis, while RNA plays a role in translating this genetic code into proteins.

Enzymes and Their Functions

Enzymes are specialized proteins that act as catalysts in biochemical reactions. They speed up reactions by lowering the activation energy, thus playing a vital role in metabolism and other cellular processes.

Importance of Biomolecules in Living Organisms

Biomolecules are fundamental to life, as they constitute the cells and perform a range of functions necessary for the survival and growth of living organisms. They are involved in everything from energy production and storage to genetic information transfer and cellular structure maintenance.

Scoring Questions for Class 12 CBSE Exams

In Class 12 CBSE exams, scoring questions on biomolecules often involve understanding their structures, functions, and roles in biological systems. Questions may include explaining the properties of different types of biomolecules, their classification, and the significance of enzymes in metabolism. Additionally, questions might cover the application of biomolecules in health and disease, making a thorough understanding of this chapter crucial for success in exams.

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NCERT Solutions for Class 12 Chemistry chapter 14-Biomolecules

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NCERT Solutions for Class 12 Chemistry

NCERT Solutions for class-12 Chemistry Chapter 14 Biomolecules is prepared by our senior and renowned teachers of Physics Wallah primary focus while solving these questions of class-12 in NCERT textbook, also do read theory of this Chapter 14 Biomolecules while going before solving the NCERT questions. Our Physics Wallah team Prepared Other Subjects NCERT Solutions for class 12.

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Chapter 14 Biomolecules

Answer the following Questions.

Question 1. What are monosaccharides?

Solution : 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.

Question 2. What are reducing sugars?

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

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

Solution : 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.

Question 4. Classify the following into monosaccharides and disaccharides.

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

Solution : Monosaccharides:

Ribose, 2-deoxyribose, galactose, fructose

Disaccharides: 

Maltose, lactose 

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

Solution : 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.

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

Solution : 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.

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

Solution : (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.

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

Solution : 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).

Question 9. What happens when D-glucose is treated with the following reagents?

(i) HI (ii) Bromine water (iii) HNO 3

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

(ii) When D-glucose is treated with Br 2 water, D- gluconic acid is produced.

(iii) On being treated with HNO 3 , D-glucose get oxidised to give saccharic acid.

Question 10. Enumerate the reactions of D-glucose which cannot be explained by its open chain structure.

Solution : (1) Aldehydes give 2, 4-DNP test, Schiff’s test, and react with NaHSO 4 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 − ∝ andβ. The ∝-form (m.p. = 419 K) crystallises from a concentrated solution of glucose at 303 K and the β-form (m.p = 423 K) crystallises from a hot and saturated aqueous solution at 371 K. This behaviour cannot be explained by the open chain structure of glucose.

Question 11. What are essential and non-essential amino acids? Give two examples of each type.

Solution : 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

Question 12. Define the following as related to proteins

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

Solution : (i) Peptide linkage:

The amide formed between −COOH group of one molecule of an amino acid and −NH 2 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 3-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.

Question 13. What are the common types of secondary structure of proteins?

Solution : There are two common types of secondary structure of proteins: 

(i) ∝-helix structure

(ii) β-pleated sheet structure

∝- Helix structure:

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.

Question 14. What type of bonding helps in stabilising the ∝-helix structure of proteins?

Solution : The H-bonds formed between the −NH group of each amino acid residue and 

Question 15. Differentiate between globular and fibrous proteins.

Question 16. How do you explain the amphoteric behaviour of amino acids?

Solution : 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.

Question 17. What are enzymes?

Solution : 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 class of substrate and some times after the particular reaction. 

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

Again, 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’.

Question 18. What is the effect of denaturation on the structure of proteins?

Solution : As a result of denaturation, globules get unfolded and helixes 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 enzyme loses its activity.

Question 19. How are vitamins classified? Name the vitamin responsible for the coagulation of blood.

Solution : 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 (B 1 , B 2 , B 6 , B 12 , etc.) and vitamin C

However, biotin or vitamin H is neither soluble in water nor in fat.

Vitamin K is responsible for the coagulation of blood.

Question 20. Why are vitamin A and vitamin C essential to us? Give their important sources.

Solution : 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). 

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. 

Question 21. What are nucleic acids? Mention their two important functions.

Solution : 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 − 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: 

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

Question 22. What is the difference between a nucleoside and a nucleotide?

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

Question 23. The two strands in DNA are not identical but are complementary. Explain.

Solution : 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.

Question 24. Write the important structural and functional differences between DNA and RNA.

Solution : The structural differences between DNA and RNA are as follows:

The functional differences between DNA and RNA are as follows:

Question 25. What are the different types of RNA found in the cell?

Solution : (i) Messenger RNA (m-RNA)

(ii) Ribosomal RNA (r-RNA)

(iii) Transfer RNA (t-RNA)

Question 26. Glucose or sucrose are soluble in water but cyclohexane or benzene (simple six membered ring compounds) are insoluble in water. Explain.

Solution : A glucose molecule contains five −OH groups while a sucrose molecule contains eight −OH groups. Thus, glucose and sucrose undergo extensive H-bonding with water.

Hence, these are soluble in water.

But cyclohexane and benzene do not contain −OH groups. Hence, they cannot undergo H-bonding with water and as a result, are insoluble in water.

Question 27. What are the expected products of hydrolysis of lactose?

Solution : Lactose is composed of β-D galactose and β-D glucose. Thus, on hydrolysis, it gives β-D galactose and β-D glucose.

Question 28. How do you explain the absence of aldehyde group in the pentaacetate of D-glucose?

Solution : D-glucose reacts with hydroxylamine (NH 2 OH) to form an oxime because of the presence of aldehydic (−CHO) group or carbonyl carbon. This happens as the cyclic structure of glucose forms an open chain structure in an aqueous medium, which then reacts with NH 2 OH to give an oxime.

But pentaacetate of D-glucose does not react with NH 2 OH. This is because pentaacetate does not form an open chain structure.

Question 29. The melting points and solubility in water of amino acids are generally higher than that of the corresponding halo acids. Explain.

Solution : Both acidic (carboxyl) as well as basic (amino) groups are present in the same molecule of amino acids. In aqueous solutions, the carboxyl group can lose a proton and the amino group can accept a proton, thus giving rise to a dipolar ion known as a zwitter ion.

Due to this dipolar behaviour, they have strong electrostatic interactions within them and with water. But halo-acids do not exhibit such dipolar behaviour. 

For this reason, the melting points and the solubility of amino acids in water is higher than those of the corresponding halo-acids.

Question 30. Where does the water present in the egg go after boiling the egg?

Solution : When an egg is boiled, the proteins present inside the egg get denatured and coagulate. After boiling the egg, the water present in it is absorbed by the coagulated protein through H-bonding.

Question 31. Why cannot vitamin C be stored in our body?

Solution : Vitamin C cannot be stored in our body because it is water soluble. As a result, it is readily excreted in the urine.

Question 32. What products would be formed when a nucleotide from DNA containing thymine is hydrolysed?

Solution : When a nucleotide from the DNA containing thymine is hydrolyzed, thymine β-D-2-deoxyribose and phosphoric acid are obtained as products.

Question 33. When RNA is hydrolysed, there is no relationship among the quantities of different bases obtained. What does this fact suggest about the structure of RNA?

Solution : A DNA molecule is double-stranded in which the pairing of bases occurs. Adenine always pairs with thymine, while cytosine always pairs with guanine. Therefore, on hydrolysis of DNA, the quantity of adenine produced is equal to that of thymine and similarly, the quantity of cytosine is equal to that of guanine.

But when RNA is hydrolyzed, there is no relationship among the quantities of the different bases obtained. Hence, RNA is single-stranded.

NCERT Solutions For Class 12 Chemistry Chapter Wise.

Chapter 1 The Solid States

Chapter 2 Solutions

Chapter 3 Electrochemistry

Chapter 4 Chemical Kinetics

Chapter 5 Surface Chemistry

Chapter 6 General Priciples and Processes of Isolation of Elements

Chapter 7 The P Block Elements

Chapter 8 The D and F Elements

Chapter 9 Coordination Compounds

Chapter 10 Haloalkanes and Haloarenes

Chapter 11 Alcohols, Phenols and Ethers

Chapter 12 Aldehydes, ketones and Carboxylics Acids

Chapter 13 Amines

Chapter 15 Polymers

Chapter 16 Chemistry In Everyday Life

Related Chapters

• chapter 14-Biomolecules
• chapter 15-Polymers
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Chemistry Worksheets Class 12 on Chapter 14 Biomolecules with Answers - Set 1

Biomolecules are the most essential organic molecules, which are involved in the maintenance and metabolic processes of living organisms. These non-living molecules are the actual foot-soldiers of the battle of sustenance of life. They range from small molecules such as primary and secondary metabolites and hormones to large macromolecules like proteins, nucleic acids, carbohydrates, lipids etc.

There are four major classes of Biomolecules – Carbohydrates, Proteins, Nucleic acids and Lipids.

Download Chemistry Worksheet Class 12 Chapter 14 Biomolecules PDF – Set 1

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CBSE Class 12 Chemistry Worksheet Chapter 14 Biomolecules – Set 1

Q1. Carbohydrates obtaining more than 10 simple units of sugar are called:

a.) Monosaccharides

b.) Disaccharides

c.) Trisaccharides

d.) Polysaccharides

Q2. Which of the following is a protein?

a.) Glycogen

b.) Amylopectin

c.) Keratin

d.) Lecithin

Q3. Night blindness may be caused by the deficiency of vitamin-

Q4. Which of the following gives maximum energy in metabolic process?

a.) Proteins

b.) Vitamins

d.) Carbohydrates

Q5. The relation between nucleotide triplets and the amino acids is called:

b.) Genetic code

c.) Replication

d.) Enzymes

Q6. How do anomers differ from epimers?

Q7. What are reducing and non reducing sugars? What is the structural feature characterising reducing sugars?

Q8. Write the formula of a tripeptide alanylglycyl phenylalanine.

Q9. Define the following terms:

a.) Anomers

b.) Peptide bond

Q10. Describe the terms D– and L– configurations used for amino acids with example.

Q11. Coagulation of egg white on boiling is an example of denaturation of protein. Explain in term of structural changes.

Q12. What are neutral, acidic and basic amino acids? Which vitamin deficiency leads to scurvy? Mention one function of Vitamin C.

Q13. What type of forces are responsible for the formation of :

a.) Cross linking of polypeptide chains

b.) ⍺-helix formation

c.) β-sheet structure

Q14. a.) What is denaturation of proteins?

b.) What type of bonds hold a DNA double helix together?

c.) Which enzyme is present in saliva? What is the function?

Q15. Differentiate between globular and fibrous proteins.

Q16. Name a disease that is caused due to deficiency of the following vitamins:

a.) Thiamine

b.) Riboflavin

Q17. Write reactions to show how glucose separately reacts with

i.) NH 2 OH

iii.) ammoniacal AgNO 3

b.) What do you understand by renaturation of proteins?

Q18. What are enzymes? How do enzymes differ from ordinary chemical catalysts? Comment on the specificity of enzyme action. What is the most important reason for their specificity?

Q19. The two strands in DNA are not identical but are complementary. Explain.

Q20 . a.) What is glycogen? How is it different from starch?

b.) How is starch structurally different from cellulose?

c.) Explain what is meant by the following:

Peptide linkage and pyranose structure of glucose.

Download PDF to access answers of Chemistry Worksheet for Class 12 Chemistry Chapter 14 Biomolecules set -1. Download PDF

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Biomolecules Class 12 Notes PDF (Handwritten & Short Notes)

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Important Questions for Class 12 Chemistry Chapter 14 Biomolecules Class 12 Important Questions

December 6, 2019 by Sastry CBSE

Biomolecules Class 12 Important Questions Very Short Answer Type

Question 1. What is meant by ‘reducing sugars’? (All India 2010) Answer: Reducing sugar contains aldehydic or ketonic group in the hemiacetal and hemiketal forms and can reduce Tollen’s reagent or Fehlmg’s solution.

Question 2. What are monosaccharides? (All India 2010) Answer: These are the simplest carbohydrates which cannot be hydrolysed to smaller molecules. Their general formula is (CH 2 O) n where n = 3 – 7 Example : glucose, fructose etc.

Question 5. What are the expected products of hydrolysis of lactose ? (Comptt. Delhi 2012) Answer: On hydrolysis, lactose gives P-D-galactose and p-D-glucose.

Question 6. Where does the water present in the egg go after boiling the egg? (Comptt. Delhi 2012) Answer: Denaturation of proteins is a process that changes the physical and biological properties of proteins without affecting the chemical composition of protein. In an egg, denaturation of protein is the coagulation of albumin present in the white of an egg. When an egg is boiled in water, the globular proteins present in it change to a rubber like insoluble mass which absorbs all the water present in the egg by making hydrogen bond with it.

Question 7. Name a water soluble vitamin which is a powerful antioxidant. Give its one natural source. (Comptt. Delhi 2012) Answer: Water soluble vitamin : Vitamin C Natural source : Amla

Question 8. What are three types of RNA molecules which perform different functions? (Delhi 2013) Answer: m-RNA, t-RNA, r-RNA

Question 9. What is a glycosidic linkage? (Delhi 2013) Answer: The two monosaccharide units are joined together through an etheral or oxide linkage formed by loss of a molecule of water. Such a linkage between two monosaccharide units through oxygen atom is called glycosidic linkage.

Question 10. What are the products of hydrolysis of sucrose? (All India 2013) Answer: Invert sugar: An equimolar mixture of glucose and fructose is obtained by hydrolysis of sucrose in presence of an acid such as dil. HC1 or the enzyme invertase or sucrase and is called invert sugar.

Question 11. Write the name of linkage joining two amino acids. (All India 2013) Answer: Peptide linkage joins two amino acids.

Question 12. Name the deficiency diseases resulting from lack of Vitamins A and E in the diet. (Comptt. Delhi 2013) Answer: Deficiency of Vitamin A causes Xerophthalmia and deficiency of Vitamin E causes Sterility.

Question 13. Name one water soluble vitamin which is a powerful antioxidant. Give its one natural source. (Comptt. Delhi 2013) Answer: Water soluble vitamin : Vitamin C Natural source : Amla

Question 14. Name one oil soluble vitamin which is a powerful antioxidant and give its one natural source. (Comptt. Delhi 2013) Answer: Oil soluble Vitamine : Vitamin D Natural source : Fish liver oil, butter, milk, eggs etc.

Question 16. Name the only vitamin which can be synthesized in our body. Name the disease caused due to the deficiency of this vitamin. (Comptt. All India 2013) Answer: Vitamin which can be synthesized in our body : Vitamin A Its deficiency causes Xerophthalmia.

Question 17. Mention one important function of nucleic acids in our body. (Comptt. All India 2013) Answer: Function of nucleic acid : Nucleic acids control the transmission of hereditary characters from one generation to another.

Question 18. Which of the two components of starch is water soluble? (Delhi 2014) Answer: Amylose is water soluble component of starch.

Question 19. Name the products of hydrolysis of sucrose. (Delhi 2014) Answer: Glucose and fructose are the products of hydrolysis of sucrose.

Question 20. Which component of starch is a branched polymer of a-glucose and insoluble in water? (Delhi 2014) Answer: Amylopectin.

Question 21. What are the products of hydrolysis of sucrose? (All India 2014) Answer: Glucose and fructose.

Question 24. Define a ‘Peptide linkage’. (Comptt. All India 2014) Answer: Peptide linkage : It is an amide linkage formed between – COOH group of one α-amino acid and NH 2 group of the other α-amino acid by loss of a molecule of water. – CO – NH – bond is called Peptide linkage.

Question 25. What are enzymes? (Comptt. All India 2014) Answer: Enzymes are protein molecules which act as catalyst in biochemical reaction.

Biomolecules Class 12 Important Questions Short Answer Type SA-I

(ii) Glycosidic linkage : The two monosaccharide units are joined together through an etheral or oxide linkage formed by loss of a molecule of water. Such a linkage between two monosaccharide units through oxygen atom is called glycosidic linkage.

Question 27. Name two water soluble vitamins, their sources and the diseases caused due to their deficiency in diet. (Delhi 2009) Answer:

Question 28. Name the four bases present in DNA. Which one of these is not present in RNA? (All India 2009) Answer: The four bases present in DNA are : (i) Adenine (A) (ii) Guanine (G) (iii) Cytosine (C) (iv) Thymine (T) In RNA, Thymine (T) is absent. It has Uracil (U) in place of Thymine.

Question 29. Name two fat soluble vitamins, their sources and the diseases caused due to their deficiency in diet. (All India 2009) Answer:

Question 30. Explain the following terms : (i) Invert sugar (ii) Polypeptides (Delhi 2009) Answer: (i) Invert sugar : An equimolar mixture of glucose and fructose obtained by hydrolysis of sucrose in presence of an acid such as dil. HCl or the enzyme invertase or sucrase is called invert sugar.

Question 32. What are essential and non-essential amino acids in human food? Give one example of each type.(Delhi 2009) Answer: Essential amino acids : Amino acids which the body cannot synthesize are called essential amino acids. Example : Valine, leucine etc. Therefore they must be supplied in diet.

Non-essential amino acids : Amino acids which the body can synthesize are called non-essential amino acids. Therefore, they may or may not be present in diet. Example : Glycine, alanine etc.

Question 35. Describe what you understand by primary structure and secondary structure of proteins. (Delhi 2009) Answer: Primary structure of proteins : Proteins may have one or more polypeptide chains. Each polypeptide in a protein has amino acids linked with each other in a specific sequence which is known as primary structure of protein.

Secondary structure of proteins : The conformation which the polypeptide chains assume as a result of hydrogen bonding is called the secondary structure of the protein.

Depending upon the size of the R groups, the two different secondary structures are possible which are :

• α-Helix structure : Intramolecular H-bonds present between the C = O of one amino acid and N – H of fourth amino acid.
• β-Pleated sheet structure : The two neighbouring polypeptide chains are held together by intermolecular H-bonds.

Question 37. Name the bases present in RNA. Which one of these is not present in DNA? (Delhi 2009) Answer: The four bases present in RNA are : Purines – Adenine (A) and Guanine (G) Pyrimidines – Uracil (U) and Cytosine (C) Uracil is not present in DNA.

Question 39. Write the main structural difference between DNA and RNA. Of the four bases, name those which are common to both DNA and RNA. (All India 2009) Answer:

The base which are common to both DNA and RNA are :

• Adenine (A)
• Guanine (G)
• Cytosine (C)

Question 40. Write such reactions and facts about glucose which cannot be explained by its open chain structure. (All India 2009) Answer: Limitations of the open chain structure of glucose :

• Glucose does not form NaHSO 3 addition product. Despite having aldehyde-ammonia group, it does not respond to 2,4-DNP test and does not respond to Schiff’s reagent test.
• Glucose penta acetate does not react with NH 2 OH due to absence of aldehydic group.

Question 41. Write any two reactions of glucose which cannot be explained by the open chain structure of glucose molecule. (Delhi 2012) Answer:

• Despite having the aldehyde group, glucose does not give 2, 4-DNP test or Schiff’s test.
• It does not form the hydrogen sulphite addition product with NaHSO 3 .
• The pentaacetate of glucose does not react with hydroxylamine indicating the absence of free – CHO group.

Question 42. Write the main structural difference between DNA and RNA. Of the two bases, thymine and uracil, which one is present in DNA? (Delhi 2012) Answer: (i) Difference between DNA and RNA :

(ii) Thymine is present in DNA.

Question 44. (a) Name the only vitamin which can be synthesized in our body. Name one disease that is caused due to the deficiency of this vitamin. (b) State two functions of carbohydrates. (Comptt. All India 2012) Answer: (a) Vitamin that can be synthesized ‘.Vitamin B 12 Disease due to the deficiency of Vitamin B 12 : Pernicious anaemia.

(b) Two functions of glucose :

• Carbohydrates such as glucose, starch, glycogen etc. provide energy for functioning of living organisms.
• Carbohydrates, especially cellulose in the form of wood is used for making furniture, houses etc. by us.

Question 46. Answer the following questions: (i) Why are vitamin A and vitamin C essential for us? (ii) What is the difference between a nucleoside and a nucleotide? (Comptt. Delhi 2014) Answer: (i) Because deficiency of vitamin A and vitamin C causes night blindness and scurvy respectively.

Question 47. Enumerate the reactions of glucose which cannot be explained by its open chain structures. (Comptt. Delhi 2014) Answer: Limitations of the open chain structure of glucose :

• Glucose does not form NaHS03 addition product. Despite having aldehyde-ammonia group, it does not give 2,4-DNP test and does not respond to Schiff’s reagent test.
• Glucose penta acetate does not react with NH2OH due to absence of aldehydic group.

Question 48. Write the ambident nucleophiles? Give an example. (Comptt. Delhi 2014) Answer: A group containing two nucleophilic centres. Example : – CN (Cyanide) and – NC (Isocynide).

Biomolecules Class 12 Important Questions Short Answer Type SA-II

Question 49. Amino acids may be acidic, alkaline or neutral. How does this happen? What are essential and non-essential amino acids? Name one of each type. (All India 2010) Answer: Amino acids can be broadly classified into three classes i.e. acidic, alkaline and neutral amino acids depending on the number of —NH 2 group and — COOH group.

Acidic amino acids : Those a-amino acids such as aspartic acid, asparagine and glutamic acid which contain two -COOH groups and one -NH 2 group are called acidic amino acids.

Alkaline or Basic amino acids : Those a-amino acids such as lysine, arginine and histidine which contain two -NH 2 groups and one -COOH group, are called basic amino acids.

Neutral amino acids : Those a-amino acids such as glycine, alanine, valine etc. which contain one -NH 2 and one – COOH group, are called neutral amino acids.

Essential amino acids : Amino acids which the body cannot synthesize are called essential amino acids. Example : Valine, leucine etc. Therefore they must be supplied in diet.

Question 50. Differentiate between fibrous proteins and globular proteins. What is meant by the denaturation of a protein? (All India 2010) Answer:

Denaturation of protein : Due to coagulation of globular protein under the influence of change in temperature, change in pH etc., the native shape of the protein is destroyed and biological activity is lost and the formed protein is called denaturated proteins and the phenomenon is denaturation.

Question 51. What is essentially the difference between a-glucose and P-glucose? What is meant by pyranose structure of glucose? (All India 2012) Answer: The two cyclic hemiacetal forms of glucose differ only in the configuration of the hydroxyl group on the first carbon atom called anomeric carbon. Such isomers i.e, α-form and β-form are called anomers. a-glucose is the monomer unit of starch and P-glucose is the monomer unit of cellulose. The six membered cyclic structure of glucose is called pyranose structure.

(ii) Primary structure : Proteins may have one or more polypeptide chains. Each polypeptide in a protein has amino acids linked with each other in a specific sequence and it is this sequence of amino acids that is called the primary structure of that protein.

(iii) Denaturation : Due to coagulation of globular protein under the influence of change in temperature, change in pH etc., the native shape of the protein is destroyed and biological activity is lost and the formed protein is called denaturated proteins and the phenomenon is denaturation.

Question 53. What are the different types of RNA found in cells of organisms ? State the functions of each type. (Comptt. Delhi 2012) Answer: Different types of RNA found in the cell are :

• Messenger RNA (mRNA): carries the message of DNA for specific protein synthesis.
• Ribosotnal RNA (rRNA) : provides the site for protein synthesis.
• Transfer RNA (t-RNA): transfers amino acids to the site of protein synthesis.

Question 54. (a) What are essential and non-essential amino acids? Give two examples of each type. (b) What are the hydrolysis products of sucrose? (Comptt. Delhi 2012) Answer: (a) Non-essential amino acids : The amino acids which can be synthesised in the body, are known as non-essential amino acids. Example : Glycine, Alanine etc.

Essential amino acids : The amino acids which cannot be synthesised in the body and must be obtained through diet are known as essential amino acids. Example : Valine, Leucine etc.

Question 55. (a) Write the structural and functional differences between DNA and RNA (b) Name two components of starch. (Comptt. Delhi 2012) Answer: (a) Structural difference :

Adenine (A)The base which are common to both DNA and RNA are :

Functional difference : DNA’s main function is to control cell activities like telling each organ what to make and what to do. RNA’s main function is to make protein.

(b) Components of starch : Amylose and amylopectin.

Question 56. (a) Give two differences between globular and fibrous proteins. (b) What change occurs in the nature of egg protein on boiling? (Comptt. Delhi 2013) Answer: (a)

(b) Because the egg comes in contact with a solution of higher osmotic pressure, the egg will shrink due to going out of water. This shrinking of egg is called plasmolysis.

Question 57. (a) How are hormones and vitamins different in respect of their source and functions? (b) Give one example each of (i) Globular protein (ii) Fibrous protein (Comptt. All India 2012) Answer: (a) Hormones are synthesized in our body and help in regulation of our body systems while vitamins are synthesized artificially in the laboratory or obtained from the food which helps in controlling many diseases.

• Globular protein : All enzymes and hormones like insulin.
• Fibrous protein : Keratin in skin, nails etc.

Question 58. (a) What are essential and non-essential amino acids? Give two examples of each. (b) How are nucleosides different from nucleotides? (Comptt. All India 2012) Answer: (a) Non-essential amino acids : The amino acids which can be synthesised in the body, are known as non-essential amino acids. Example : Glycine, Alanine etc.

Question 59. (i) Deficiency of which vitamin causes night-blindness? (ii) Name the base that is found in nucleotide of RNA only. (iii) Glucose on reaction with HI gives n-hexane. What does it suggest about the structure of glucose? (Delhi 2014) Answer: (i) Vitamin A causes night blindness. (ii) Uracil is found in nucleotide of RNA only. (iii) It suggests the open structure of glucose.

Question 63. Define the following terms : (i) Glycosidic linkage (ii) Invert sugar (iii) Oligosaccharides (All India 2014) Answer: (i) Glycosidic linkage : The two monosaccharide units are joined together through an etheral or oxide linkage formed by loss of a molecule of water. Such a linkage between two monosaccharide units through oxygen atom is called glycosidic linkage

(ii) Invert sugar : An equimolar mixture of glucose and fructose obtained by hydrolysis of sucrose in presence of an acid such as dil. HC1 or the enzyme invertase or sucrase is called invert sugar.

(iii) Oligosaccharides : Those carbohydrates which on hydrolysis give 2-10 molecules of monosaccharides are called oligosaccharides. Example : sucrose, maltose.

(ii) Anomers : A pair of stereoisomers which differ in configuration only around C 1 are called anomers. Two isomers are said to be anomers if the isomerisation in the molecule is at first carbon.

(iii) Essential amino acids: Essential amino acids : Amino acids which the body cannot synthesize are called essential amino acids. Example : Valine, leucine etc. Therefore they must be supplied in diet.

Non-essential amino acids : Amino acids which the body can synthesize are called non-essential amino acids. Therefore, they may or may not be present in diet. Example ; Glycine, alanine etc.

Question 65. What are essential and non-essential amino acids? Give two examples of each. (Comptt. All India 2014) Answer: Essential amino acids : Amino acids which the body cannot synthesize are called essential amino acids. Example : Valine, leucine etc. Therefore they must be supplied in diet.

Question 66. (i) Which one of the following is a disaccharide : Starch, Maltose, Fructose, Glucose? (ii) What is the difference between fibrous protein and globular protein? (iii) Write the name of vitamin whose deficiency causes bones deformities in children. (Delhi 2014) Answer: (i) Maltose is a disaccharide.

(iii) Vitamin D

Question 67. (i) Which one of the following is a polysaccharide : Starch, Maltose, Fructose, Glucose? (ii) What one difference between a-helix and P-pleated sheet structure of protein. (iii) Write the name of the disease caused by the deficiency of Vitamin B 12 . (All India 2015) Answer: (i) Starch is a polysaccharide. (ii) α-Helix structure : The polypeptide chains are held together (stabilized) by intramolecular H-bonding. β-Pleated sheet structure : The two neighbouring polypeptide chains are held together by intermolecular , H-bonding. (iii) Disease caused by the deficiency of Vitamin B 12 is Pernicious anaemia.

Question 68. How are vitamins classified? Name the vitamin responsible for the coagulation of blood. (Comptt. Delhi 2015) Answer: Vitamins are classified into two types :

• Water insoluble vitamins : These are fat soluble substances E.g. Vitamin A, D, E and K.
• Water soluble vitamins : These include Vitamin B-Complex and Vitamin C (except B 12 ). Vitamin K or phylloquinone is responsible for the coagulation of blood.

Question 71. (i) Write the structural difference between starch and cellulose. (ii) What type of linkage is present in Nucleic acids? (iii) Give one example each for fibrous protein and globular protein. (All India 2016) Answer: (i) Starch contains the β-D-glucose as its monomer units while cellulose contains β-D- glucose as its monomer units. (ii) Phosphodiester linkages are present in Nucleic Adds (iii) Globular protein : All enzymes and hormones like insulin. Fibrous protein : Keratin in skin.

Question 72. Define the following as related to proteins : (i) Peptide linkage (ii) Primary structure (iii) Denaturation (Comptt. Delhi 2016) Answer: (i) Peptide linkage : Two amino acids of same type or different types combine together by the elimination of H 2 O molecule to form – CONH- linkage. (ii) Primary structure : It refers to the sequence in which amino acids are joined. (iii) Denaturation : When a native protein is subjected to change in temperature or pH, hydrogen bonds get disturbed and globules get uncoiled and proteins lose their biological activity.

Question 73. What are enzymes? Describe their functions. Name two diseases which are caused due to deficiency of enzymes. (Comptt. All India 2016) Answer: Enzymes are protein molecules which acts catalyst in Biochemical Reactions (biocatalyst). They increase the rate of biochemical reactions. For example : Zymase, Invertase etc. Two diseases due to deficiency of enzymes are : Anemia, Gauchea’s disease.

Question 74. (a) What type of linkage is present in disaccharides? (b) Write one source and deficiency disease of vitamin B 12 . (c) Write the difference between DNA and RNA. (Comptt. Delhi 2016) Answer: (a) Glycosidic linkage is present in disaccharides. (b) Eggs are the source of Vitamin B 12 and its deficiency causes pernicious anaemia. (c) DNA is a double strand while RNA is a single strand molecule.

Question 76. (a) Why water soluble vitamins must be supplied regularly in the diet? Give one example of it. (b) Differentiate between the following : (i) Essential and non-essential amino acids. (ii) Fibrous and globular proteins. Answer: (a) Water soluble vitamins must be supplied regularly in the diet because they are regularly excreted in urine and cannot be stored in our body. For eg., Vitamin C, Vitamin B, etc. (b) (i) Essential amino acids : Amino acids which the body cannot synthesize are called essential amino acids. Example : Valine, leucine etc. Therefore they must be supplied in diet.

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