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Important Questions for CBSE Class 12 Chemistry – Biomolecules

  

Important Questions for CBSE Class 12 Chemistry – Biomolecules

PREVIOUS YEARS QUESTIONS

2O15

Short Answer Type Questions [II] [3 Marks]

Question 1:
(i)Which one of the following is a disaccharide:
starch, maltose, fructose, glucose?
(ii) What is the difference between acidic amino acid and basic amino acid?
(iii) Write the name of the linkage joining two nucleotides.
Answer:
(i) Maltose
(ii) Acidic amino acid contains 2 carboxylic acids groups and 1 amino group. Basic amino acids contain 2 amino and one —COOH group.
(iii) Phospho diester linkage.

Question 2:
(i) Which one of the following is an oligosaccharide:
starch, maltose, fructose, glucose
(ii) What is the difference between DNA and RNA.
(iii) Write the name of the disease caused by the deficiency of vitamin B1
Answer:
(i) Maltose
(ii) DNA is Deoxyribonucleic acid, whereas RNA is Ribonucleic acid. DNA has Thymin, RNA has Uracil.
(iii) Beri-Beri.

Question 3:
(i) Write the product obtained when D-glucose reacts with HCN.
(ii) What type of bonding stabilizes the α-helix structure of proteins?
(iii) Write the name of the disease caused by the deficiency of vitamin B12

.
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 1
(ii) H-Bonding
(iii) Pernicious anaemia.

Question 4:
(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 bone deformities in children.
Answer:
(i) Maltose is disaccharide.
(ii) Fibrous proteins have thread like structure and are insoluble in water. Globular proteins form a-helix and are soluble in water.
(iii) Vitamin D.

Question 5:
(i) Which one of the following is a polysaccharide: starch, maltose, fructose, glucose
(ii) Write one difference between α-helix and β-pleated sheet structures of protein.
(iii) Write the name of the disease caused by the deficiency of vitamin B12
Answer:
(i) Starch
(ii) α-helix structure has intra-molecular H-bonding in polypeptide chains of globular proteins.
β-pleated structure has inter-molecular H-bonding between polypeptide chains of fibrous proteins.
(iii) Pernicious Anaemia.

Question 6:
(i) Which one of the following is a monosaccharide: starch, maltose, fructose, cellulose
(ii) What is the difference between acidic amino acids and basic amino acids?
(iii) Write the name of the vitamin whose deficiency causes bleeding of gums.
Answer:
(i) Fructose is monosaccharide.
(ii) Refer Ans. to Q.1(ii).
(iii) Deficiency of Vitamin ‘C’ causes bleeding of gums.

Question 7:
(i) Write the product obtained when D-glucose reacts with H2N—OH
(ii) Amino acids show amphoteric behaviour why?
(iii) Why cannot vitamin C be stored in our body.
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 2
(ii) It is because they have acidic as well as basic group.
(iii) It is because Vitamin ‘C’ is soluble in water.

Question 8:
(i) Write the product obtained when D-glucose reacts with Br2 water.
(ii) What type of linkage is present in proteins?
(iii) Write one difference between DNA and RNA?
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 3

Question 9:
(i) Which one of the following is a polysaccharide: starch, maltose, fructose, glucose
(ii) What is the difference between native protein and denatured protein?
(iii) Write the name of the vitamin responsible for the coagulation of blood.
Answer:
(i) Starch
(ii) Native protein is biologically active, whereas denatured protein loses biological activity and its secondary and tertiary structures are ruptured.
(iii) Vitamin K.

2014

Very Short Answer Type Questions [1 Mark]

Question 10:
Which of the two components of starch is water soluble?
Answer:
Amylose is water soluble component in starch.

Question 11:
Which component of starch is a branched polymer of α-glucose and insoluble in water?
Answer:
Amylopection.

Question 12:
What are the products of hydrolysis of sucrose?
Answer:
Glucose and Fructose.

Question 13:
What are the products of hydrolysis of maltose?
Answer:
2 moles of Glucose

Question 14:
Write the products of hydrolysis of lactose.
Answer:
Glucose and Galactose.

Question 15:
Name the two components of α-glucose which constitute starch.
Answer:
Amylose and amylopectin are two components of starch.

Question 16:
What are biocatalysts? Give an example.
Answer:
Those catalysts which catalyse biochemical reactions are called biocatalysts
e.g. invertase catalyses hydrolysis of cane-sugar to form glucose and fructose.

Short Answer Type Questions [II] [3 Marks]

Question 17:
(i) Deficiency of which vitamin causes rickets?
(ii) Give an example for each of fibrous protein and globular protein.
(iii) Write the product formed on reaction of D-glucose with Br2water.
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 4

Question 18:
(i) Deficiency of which vitamin causes scurvy?
(ii) What type of linkage is responsible for the formation of proteins?
(iii) Write the product formed when glucose is treated with HI
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 5

Question 19:
Define the following terms as related to proteins:
(i) Peptide linkage
(ii) Primary structure
(iii) Denaturation
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 6

Question 20:
Define the following terms:
(i) Glycosidic linkage
(ii) Invert sugar
(iii) Oligosaccharides
Answer:
(i) The oxide linkage between monosaccharides in oligo and poly saccharides is called glycosidic linkage.
(ii) The mixture of glucose and fructose is called invert sugar.
(iii) Those saccharides which give 2 to 10 molecules of monosaccharides on hydrolysis are called oligosaccharides.

Question 21:
Define the following terms:
(i) Nucleotide
(ii) Anomers
(iii) Essential amino acids
Answer:
(i) Nucleotides: These are the monomers of nucleic acid. They consist of heterocyclic base, pentose sugar and phosphoric acid residue.
(ii) Anomers: Those compounds which differ in orientation of —OH group on C-l carbon atom are called anomers, e.g. a-glucose and b-glucose.
(iii) Essential amino acids: Those amino acids which are not synthesised by our body and must be a part of our diet are called essential amino acids.

Question 22:
Define the following terms:
(a)Anomers
(b) Denaturation of proteins
(c) Essential amino acids
Answer:
(a) Refer Ans. to Q.21
(b) (c) Refer Ans. to Q.21 (iii)
(b) Refer Ans. to Q.19 (iii)

Question 23:
Define the following terms:
(a) Invert sugar
(b) Vitamins
(c) Nucleoside
Answer:
(a) Invert sugar: It is a mixture containing equal amount of glucose and fructose.
(b) Vitamins: Vitamins are the group of organic compounds which are required in very small amounts for the healthy growth and functioning of animal organism. They cannot be made by organism and so have to be part of our diet. The deficiency of a vitamin can cause a specific disease. Vitamins A, D, E and K are fat-soluble substances, whereas vitamin B complex and vitamin C are water-soluble.
(c) Nucleosides: Abase joined to a sugar molecule is called nucleoside, e.g. adenosine contains adenine and ribose, guanosine contains ribose and guanine, cytidine contains ribose and cytosine.

Question 24:
Define the following terms:
(a)Polysaccharides
(b) Amino acids
(c) Enzymes
Answer:
(a) Polysaccharides: These carbohydrates which give large number of mono- Sachharides on hydrolysis are called polysaccharides.
(b) Amino acids: Those compounds which contain amino group as well as carboxylic acid group are called amino acids.
(c) Enzymes: These are biological catalyst which catalyse specific biochemical reactions.

2013

Very Short Answer Type Questions [1 Mark]

Question 25:
What are three types of RNA molecules which perform different functions?
Answer:
(i) r-RNA (ribosomal RNA)
(ii) m-RNA (messenger RNA)
(iii)t-RNA (transfer RNA)

Question 26:
What type of bonding helps in stabilising the a-helix structure of proteins?
Answer:
H-bonding.

Question 27:
What are the products of hydrolysis of sucrose?
Answer:
Glucose and fructose

Question 28:
What are the products of hydrolysis of lactose?
Answer:
Glucose and galactose

Question 29:
What is a glycosidic linkage?
Answer:
Refer Ans. to Q.20 (i)

Question 30:
Write the name of linkage joining two amino acids.
Answer:
Peptide linkage.

Short Answer Type Questions [2 Marks]

Question 31:

(a) What type of bonding helps in stabilising the a-helix structure of proteins?
(b) What is the structural difference between a nucleoside and a nucleotide?
Answer:
(a) Hydrogen bonding
(b) Nucleoside contains heterocyclic base and sugar, e.g. Adenosine.
Nucleotide contains heterocyclic base, sugar and phosphoric acid residue, e.g. Adenosine triphosphate(ATP).

Question 32:
Write the reactions involved when D-glucose is treated with the following reagents:
(a) HCN (b) Br2 water
Answer:
(a) Refer Ans. to Q.3 (i) (b) Refer Ans. to Q.8 (i).

Question 33:
Write the reactions involved when D-glucose is treated with the following reagents.
(a) HI (b) H2N—OH
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 7

Question 34:
Write the structural difference between DNA and RNA.
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 8

Value Based Questions

Question 35:
After watching a programme on TV about the adverse effects of junk food and soft drinks on the health of t school children, Sonali, a student of Class XII, discussed the issue with the school principal. The principal immediately instructed the canteen contractor to replace the fast food with the fibre and vitamins rich food like sprouts, salad, fruits, etc. This decision was welcomed by the parents and the students.
After reading the above passage, answer the following questions:
(a) What values are expressed by Sonali and the Principal of the school?
(b) Give two examples of water-soluble vitamins.
Answer:
(a) Sonali and the Principal have shown sincere concern about the health of
school children. School Principal acted fast to implement his decision and his value of accepting right suggestion is appreciable.
(b) Vitamin B and Vitamin C are soluble in water.

Question 36:
Shanti, a domestic helper of Mrs. Anuradha, fainted while mopping the floor. Mrs. Anuradha immediately took her to the nearby hospital where she was diagnosed to be severely ‘anaemic’. The doctor prescribed an iron rich diet and multivitamins supplement to her. Mrs. Anuradha supported her financially to get the medicines. After a month, Shanti was diagnosed to be normal. After reading the above passage, answer the following questions:
(i) What values are shown by Mrs. Anuradha?
(ii) Name the vitamin whose deficiency causes ‘pernicious anaemia’.
(iii) Give an example of a water-soluble vitamin.
Answer:
(i) She is a kind hearted woman, has helping nature and is a good human being.
(ii) Vitamin B12
(iii) Vitamin C is soluble in water.

2012

Very Short Answer Type Questions [1 Mark]

Question 37:
What is meant by biocatalysts?
Answer:
Refer Ans. to Q.16.

Question 38:
Write the full forms of DNA and RNA.
Answer:
DNA stands for Deoxyribonucleic acid, whereas RNA stands for Ribonucleic acid.

Question 39:
Write the structure of the product obtained when glucose is oxidised with nitric acid.
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 9

Question 40:
Write a reaction which shows that all the carbon atoms in glucose are linked in a straight chain.
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 10

Question 41:
Of the two bases named below, which one is present in RNA and which one is present in DNA?
(i) Thymine (ii) Uracil
Answer:
RNA has uracil, DNA has Thymine.

Short Answer Type Questions [I] [2 Marks]

Question 42:
Write the main structural difference between DNA and RNA. Of the two bases, thymine and uracil, which one is present in DNA?
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 11

Question 43:
Write any two reactions of glucose which cannot be explained by open chain structure.
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 12

Question 44:
What is meant by
(i) Peptide linkage? (ii) Biocatalystics?
Answer:
(i) Refer Ans. to Q.19 (i) (ii) Refer Ans. to Q.16

Short Answer Type Questions [II] [3 Marks]

Question 45:
What is essentially the difference between a-glucose and b-glucose? What is meant by pyranose structure of glucose?
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 13

Question 46:
What is glycogen? How is it different from starch? How is starch structurally different from cellulose?
Answer:
Glycogen is a polysaccharide stored in animal body. It is also called animal starch. It is highly branched.
Starch is also polysaccharide stored in plants. It has amylose (linear) and amylopectin which is highly branched. Starch is branched chain polymer of a-glucose. Cellulose is a linear polymer of p-glucose. It is present in cell walls of plants. It is not digested by human beings.

Question 47:
Define the following as related to proteins
(i) Peptide linkage
(ii) Primary structure
(iii) Denaturation
Answer:
(i) Refer Ans. to Q.19 (i)
(ii) Refer Ans. to Q.19 (ii).
(iii) Refer Ans. to Q.19 (iii)

Question 48:
Explain the meaning of the following terms:
(i) Invert sugar
(ii) Polypeptides
(iii) Enzymes
Answer:
(i) Refer Ans. to Q.20 (ii)
(ii) Those compounds which are formed by large number of amino acids involving peptide bonds are called polypeptides.
(iii) Refer Ans. to Q.24 (c).

Question 49:
Write three such behaviours of glucose which cannot be explained by an open chain structure of glucose molecule. What alternative structure has been proposed for the glucose molecule?
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 14
Important Questions for CBSE Class 12 Chemistry - Biomolecules 15

2011

Very Short Answer Type Questions [1 Mark]

Question 50:
Name the deficiency diseases resulting from lack of vitamins A and E in the diet.
Answer:
(i) Night blindness
(ii) Loss of reproduction power.

Short Answer Type Questions [I] [2 Marks]

Question 51:
What is essentially the difference between a-form of glucose and p-form of glucose? Explain.
Answer:
(i)α-glucose and β-glucose differ in position of -OH group on C-l position, therefore, these are called anomers.
(ii) They differ in specific rotation (optical rotation).
(iii) They differ in melting points.

Question 52:
State what you understand by primary structure and secondary structure of proteins.
Answer:
Primary structure of protein: The sequence in which the amino acids are arranged in a protein is called the primary structure of protein.
Secondary structure of protein: The polypeptide chain gets folded due to intramolecular hydrogen bonding between the carboxyl and amino groups. In an a-helix, the peptide chain coils and the turns of the coil are held together by hydrogen bonds. Another type of secondary structure is possible in which the protein chains are stretched out. This is the P-pleated sheet structure.

Question 53:
Explain what is meant by
(i) a peptide linkage,
(ii) a glycosidic linkage.
Answer:
(i) Refer Ans. to Q.19 (i)
(ii) Refer Ans. to Q.20 (i)

Question 54:
Name the bases present in RNA. Which one of these is not present in DNA?
Answer:
Uracil, Cytocine, Guanine and Adenine are present in RNA.
Uracil is not present in DNA.

Question 55:
Write the main structural difference between DNA and RNA. Of the four bases, name those which are common to both DNA and RNA.
Answer:
DNA has double helix structure, whereas RNA is single helix. Adenine, Guanine, Cytocine are bases common to both RNA and DNA.

Question 56:
Name the products of hydrolysis of
(i) sucrose and
(ii) lactose.
Answer:
(i) Glucose and fructose
(ii) Glucose and galactose

Question 57:
Write such reactions and facts about glucose which cannot be explained by its open chain structure.
Answer:
Refer Ans. to Q.43.

Question 58:
Explain what is meant by the following:
(i) peptide linkage
(ii) pyranose structure of glucose
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 16

Short Answer Type Questions [II] [3 Marks]

Question 59:
“The two strands of DNA are not identical but are complementary.” Explain.
Answer:
DNA consists of two strands of polynucleotides coiled around each other in the form of a double helix. The nucleotides making up each strand of DNA are connected by phosphodiester bonds. This forms the backbone of each DNA strand from which the bases extend. The bases of one strand of DNA are paired with bases on the other strand by means of hydrogen bonding. This hydrogen bonding is very specific as the structures of bases permit only one mode of pairing. Adenine pairs only thymine through two hydrogen bonds and guanine pairs with cytosine through three hydrogen bonds. The two strands of DNA are said to be complementary to each other in sense that the sequence of bases in one strand automatically determines that of the other. These strands are not identical but complementary.

2010

Very Short Answer Type Questions [1 Mark]

Question 60:
What is meant by ‘reducing sugars’?
Answer:
Those sugars which have free aldehyde group and give brick red precipitate with Fehling’s solution.

Question 61:
Give an example each of the following:
(i) Reducing sugar (ii) Non-reducing sugar
Answer:
(i) Glucose
(ii) Sucrose

Question 62:
What are monosaccharides?
Answer:
Those carbohydrates which cannot be hydrolysed are called monosaccharide.

Question 63:
What are the products of hydrolysis of sucrose?
Answer:
Sucrose on hydrolysis gives glucose and fructose.

Question 64:
What happens when glucose is treated with bromine water?
Answer:
Refer Ans. to Q.17 (iii).

Question 65:
What happens when glucose reacts with nitric acid?
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 17

Short Answer Type Questions [I] [2 Marks]

Question 66:
Explain the following terms:
(i) Invert sugar
(ii) Polypeptides
Answer:
(i) Refer Ans. to Q.20 (ii)
(ii) Refer Ans. to Q. 48 (ii).

Question 67:
What are essential and non-essential amino acids in human food? Give one example of each type.
Answer:
Essential amino acids: Those amino acids which are not synthesised by our body are called essential amino acids. They must be a part of our diet. Valine is an essential amino acid.
Non-essential amino acids: They are synthesised by our body. They are also called dispensable amino acids, e.g. glycine.

Question 68:
What are vitamins? Deficiency of which vitamin causes
(i) Pernicious anaemia?
(ii) Convulsions?
Answer:
Vitamins: Vitamins are the group of organic compounds which are required in very small amounts for the healthy growth and functioning of animal organism. They cannot be made by organism and so have to be the part of our diet. The deficiency of a vitamin can cause a specific disease.
(i) Vitamine B12 deficiency causes pernicious anaemia
(ii) Vitamine B2 deficiency causes convulsion.

Question 69:
State what the following are and how they differ from each other:
(i) a nucleotide and
(ii) a nucleoside.
Answer:
(i) Nucleotides: They are the monomers of nucleic acids. They are made up of a heterocyclic base containing nitrogen, a five carbon sugar and a phosphate group, e.g. adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP). They contain P—O — P bonds which are high energy phosphate bonds and due to these bonds, nucleotides are energy carriers.
or
Sugar + Phosphate + Heterocyclic base.
(ii) Nucleosides: A base joined to a sugar molecule is called nucleoside, e.g. adenosine contains adenine and ribose, guanosine contains ribose and guanine, cytidine contains ribose and cytosine.
or
Sugar + Heterocyclic base.

Question 70:
Name the products of hydrolysis of sucrose. Why is sucrose not a reducing sugar?
Answer:
Glucose and Fructose.

Short Answer Type Questions [II] [3 Marks]

Question 71:
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.
Answer:
Acidic amino acids: Those amino acids which contain two carboxyl groups and one amino group are called acidic amino acids, e.g. Aspartic acid.
Basic or alkaline amino acids: Those amino acids which contain two amino groups and one carboxyl group are called basic amino acids, e.g. Arginine. Neutral amino acids: Those amino acids which contain one amino group and one carboxyl group are called neutral amino acids, e.g. Glycine.
Essential amino acids: Those amino acids which are not synthesised by our body are called essential amino acids. They must be a part of our diet. Their deficiency leads to diseases, such as Kwashiorkor (water balance in the body is disturbed), e.g. Leucine.
Non-essential amino acids: They are synthesised by our body. They are also called dispensable amino acids, e.g. Serine.

Question 72:
Differentiate between fibrous proteins and globular proteins. What is meant by the denaturation of a protein.
Answer:
Fibrous proteins have thread like structures insoluble in water. Globular proteins have spherical structure, soluble in water. The rupture of secondary and tertiary structure of proteins by heating or change in pH is called denaturation of protein.

Question 73:
Explain the meanings of the following terms:
(i) Invert sugar
(ii) Peptide linkage
(iii) Denaturation of proteins.
Answer:
(i) Refer Ans. to Q.20 (ii)
(ii) Refer Ans. to Q.19 (i).
(iii) Refer Ans. to Q.19 (iii)

Question 74:
Mention three such facts/reactions about glucose which cannot be explained by its open end structure. What is meant by pyranose structure of glucose.
Answer:
Refer Ans. to Q.49.

2009

Short Answer Type Questions [I] [2 Marks]

Question 75:
Name two water soluble vitamins, their sources and the diseases caused due to their deficiency in diet.
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 18

Question 76:
Name the four bases present in DNA. Which one of these is not present in RNA?
Answer:
DNA contains, Adenine, Thymine, Guanine and Cytosine.
Thymine is not present in RNA. Instead of Thymine, RNA contains Uracil.

Question 77:
Name two fat soluble vitamins, their sources and the diseases caused due to their deficiency in diet.
Answer:
Important Questions for CBSE Class 12 Chemistry - Biomolecules 19

Question 78:
Explain what is meant by
(i) a peptide linkage
(ii) a glycosidic linkage
Answer:
(i) Refer Ans. to Q.19 (i)
(ii) Refer Ans. to Q.20 (i)

Question 79:
What are the following substances
(i) Invert sugar (ii) Polypeptides
Answer:
(i) Refer Ans. to Q.19 (ii)
(ii) Refer Ans. to Q.48 (ii)

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