TEST

BIOMOLECULES
Class 12 - Chemistry
Time Allowed: 2 hours and 59 minutes Maximum Marks: 190

Section A
1. What happens when D-Glucose is treated with the following reagents: [2]
a. Br2 water

b. HCN
c. (CH3CO)2O

2. What is denaturation and renaturation of proteins? [2]

3. How do you explain the amphoteric behaviour of amino acids? [2]
4. What is the difference between Nucleotide and Nucleoside? [2]
5. Give any two points of difference between globular and fibrous proteins. [2]
6. a. Name the three major classes of carbohydrates and give the distinctive characteristic of each class. [2]
b. What are nucleotides? Name two classes of nitrogen containing base found amongst nucleotides.
7. Give the reaction of heating glucose with hydroxylamine. Presence of which group is confirmed by this [2]
reaction?
8. What is the effect of denaturation on the structure of proteins? [2]
9. The activation energy for the acid-catalyzed hydrolysis of sucrose is 6.22 kJ mol–1, while the activation energy [2]

is only 2.15 kJ mol–1 when hydrolysis is catalyzed by the enzyme sucrase. Explain.
10. Give Chemical equation for the following reactions: [2]
i. Propanone is treated with dil. Ba(OH)2.
ii. Acetophenone is treated with Zn(Hg)/Conc.HCl
iii. Benzoyl chloride is hydrogenated in presence of Pd-BaSO4.

11. Where does the water present in the egg go after boiling the egg? [2]
12. Define the following with an example of each: [2]
a. Polysaccharides
b. Denatured protein
c. Essential amino acids

13. a. Give any one property of glucose that cannot be explained by the open chain structure. [2]
b. Compare amylase with amylopectin in terms of constituting structure.
c. Why do amino acids show amphoteric behaviour?

14. a. Write the product when D-glucose reacts with conc. HNO3. [2]

b. Amino acids show amphoteric behaviour. Why?

c. Write one difference between α-helix and β-pleated structure of protein.
15. Define the following terms: [2]
i. Oligosaccharides

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 ii. Invert sugar
16. Classify the following into monosaccharides and disaccharides. [2]
Ribose, 2-deoxyribose, maltose, galactose, fructose and lactose.
17. Differentiate between the following: [2]
a. Fibrous protein and Globular protein
b. Essential amino acids and Non-essential amino acids
c. Amylose and Amylopectin
18. Define the following with a suitable example in each: [2]
i. Oligosaccharides
ii. Fibrous protein
iii. Vitamins
19. Under what conditions glucose is converted to gluconic and saccharic acid? [2]
20. Why are carbohydrates generally optically active? [2]
21. a. What is the difference between native protein and denatured protein? [2]
b. Which one of the following is a disaccharide:
Glucose, Lactose, Amylose, Fructose
c. Write the name of the vitamin responsible for the coagulation of blood.

22. i. What type of linkage is present in disaccharides? [2]

ii. Write one source and deficiency disease of vitamin B12.

iii. Write the difference between DNA and RNA

23. a. What are the hydrolysis products of (i) Lactose, (ii) Maltose? [2]
b. Give the basic structural difference between starch and cellulose.
24. Define the following terms with a suitable example in each: [2]
a. Polysaccharides
b. Denatured protein
c. Fibrous protein
25. Give reasons for any 3 of the following observations: [2]
a. Penta-acetate of glucose does not react with hydroxylamine.
b. Amino acids behave like salts.
c. Water soluble vitamins must be taken regularly in diet.
d. The two strands in DNA are complimentary to each other.
26. What is peptide bond? Illustrate. [2]
27. Write the reactions involved when D-glucose is treated with the following reagents: [2]
i. Br2 water
ii. H2N-OH
iii. (CH3CO)2O

28. Why is cellulose in our diet not nourishing? [2]

29. What are the hydrolysis product of (i) Sucrose and (ii) Lactose. [2]
30. Name the main disease caused due to lack of vitamin and its source in each of the following: A, B6 and E. [2]
31. Mention the type of linkages responsible for the formation of the following: [2]

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 i. Primary structure of proteins
ii. Cross-linking of polypeptide chains
iii. α-helix formation
iv. β-sheet structure

32. i. A non-reducing disaccharide A on hydrolysis with dilute acid gives an equimolar mixture of D-(+)-glucose [2]
and D-(-)-Fructose.
HCl

A+H2O −−→ C6H12O6 + C6H12O6

[α]D = +66.5o + 52.5o - 92.4o

Identify A. What is the mixture of D-(+)-glucose and D-(-)-Fructose known as? Name the linkage that holds
the two units in the disaccharide.
ii. α-amino acids have relatively higher melting points than the corresponding halo acids. Explain

33. i. Glucose reacts with acetic anhydride in presence of pyridine to form pentaacetyl derivative of glucose. What [2]
does this reaction indicate?
ii. How will you distinguish 1o and 2o hydroxyl groups in glucose? Explain with reaction.
34. Write the structure of product when D-Glucose reacts with the following: (any three) [2]
a. HI
b. Conc.HNO3
c. Br2 water
d. HCN
35. Coagulation of egg white on boiling is an example of denaturation of protein. Explain it in terms of structural [2]
changes.
Section B
36. What happens when D-glucose is treated with the following reagents [3]
a. HI
b. Bromine water
c. HNO3

37. Give a plausible explanation for the following: [3]

i. Glucose doesn't give a 2,4-DNP test.
ii. The two strands in DNA are not identical but are complementary.
iii. Starch and cellulose both contain glucose unit as monomer, yet they are structurally different.
38. What are nucleic acids? Mention their two important functions. [3]
39. What is the difference between a nucleoside and a nucleotide? [3]
40. Define enzymes. What is the most important reason for their specific in action. [3]
41. a. What is denaturation and renaturation of proteins? [3]
b. Give reason- Amylase present in the saliva becomes inactive in the stomach.
42. What do you understand by the term glycosidic linkage? [3]
43. What is glycogen? How is it different from starch? [3]
44. What are the common types of secondary structure of proteins? [3]
45. Differentiate the following: [3]
i. Fibrous protein and Globular protein

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 ii. Essential amino acids and Non-essential amino acids
iii. DNA and RNA
46. Differentiate between following: [3]
i. Amylose and Amylopectin
ii. Globular protein and Fibrous protein
iii. Nucleotide and Nucleoside
47. Define the following and give one example of each: [3]
a. Isoelectric point,
b. Mutarotation
c. Enzymes.
48. What are nucleotides? Name two classes of nitrogen containing bases found amongst nucleotides. [3]
49. Write the reaction of Glucose with: [3]
i. HCN
ii. Br2
iii. HI
50. What are enzymes? [3]
51. Differentiate between the following: [3]
i. Amylose and Amylopectin
ii. Peptide linkage and Glycosidic linkage
iii. Fibrous proteins and Globular proteins
52. Define the terms as related to proteins: [3]
i. Peptide linkage
ii. Primary structure
iii. Denaturation
53. What are the expected products of hydrolysis of lactose? [3]
54. Define the following as related to proteins. [3]
a. Peptide linkage
b. Primary structure
c. Denaturation
55. Write chemical reactions to show that open structure of D-glucose contains the following: [3]
i. Straight chain
ii. Five alcohol groups
iii. Aldehyde as carbonyl group
56. Define the following and give one example of each: [3]
a. Isoelectric point
b. Mutarotation
c. Enzymes
57. Define the following terms with a suitable example of each: [3]
a. Anomers
b. Essential amino acids

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 c. Denaturation of protein
58. Enumerate the reactions of D-glucose which cannot be explained by its open chain structure. [3]
59. Define the following : [3]
i. Co-enzymes
ii. Mutation in biomolecules
iii. Nucleotides
60. What happens when D-glucose is treated with the following reagents? [3]
i. HI
ii. Bromine water
iii. HNO3

Section C
61. Read the following text carefully and answer the questions that follow: [4]
Carbohydrates can exist in either of two conformations, as determined by the orientation of the hydroxyl group
about the asymmetric carbon farthest from the carbonyl.

By convention, a monosaccharide is said to have D-configuration if the hydroxyl group attached to the
asymmetric carbon atom adjacent to the - CH2OH group is on the right-hand side irrespective of the positions of

the other hydroxyl groups. On the other hand, the molecule is assigned L-configuration if the - OH group
attached to the carbon adjacent to the - CH2OH group is on the left-hand side.

i. D-Glyceraldehyde and L-Glyceraldehyde are (1)

ii. The two functional groups present in a typical carbohydrate are (1)
iii. Which of the monosaccharides, is the majority found in the human body? (2)
OR
The correct corresponding order of names of four aldoses with configuration given below (2)

respectively, is
62. Read the following text carefully and answer the questions that follow: [4]
Carbohydrates are optically active polyhydroxy aldehydes and ketones. They are also called saccharides. All
those carbohydrates which reduce Fehling’s solution and Tollen’s reagent are referred to as reducing sugars.
Glucose, the most important source of energy for mammals, is obtained by the hydrolysis of starch. Vitamins are
accessory food factors required in the diet. Proteins are the polymers of α-amino acids and perform various
structural and dynamic functions in the organisms. Deficiency of vitamins leads to many diseases.
i. The penta-acetate of glucose does not react with Hydroxylamine. What does it indicate? (1)
ii. Why cannot vitamin C be stored in our body? (1)

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 iii. Define the following as related to proteins: (2)
i. Peptide linkage
ii. Denaturation
OR
Define the following as related to carbohydrates: (2)
i. Anomers
ii. Glycosidic linkage
63. Read the following text carefully and answer the questions that follow: [4]
Pentose and hexose undergo intramolecular hemiacetal or hemiketal formation due to combination of the -OH
group with the carbonyl group. The actual structure is either of five or six membered ring containing an oxygen
atom. In the free state all pentoses and hexoses exist in pyranose form (resembling pyran). However, in the
combined state some of them exist as five membered cyclic structures, called fiiranose (resembling furan).

The cyclic structure of glucose is represented by Haworth structure:

α and β-D-glucose have different configurations at anomeric (C-1) carbon atom, hence are called anomers and
the C-1 carbon atom is called anomeric carbon (glycosidic carbon).
The six-membered cyclic structure of glucose is called the pyranose structure.
i. What percentage of β-D-(+) glucopyranose is found at equilibrium in the aqueous solution? (1)
ii. The following carbohydrate is (1)

iii. In the carbon structure, anomeric carbon is (2)

OR
What are α-D(+)-glucose and β-D(+)glucose? (2)
64. Read the following text carefully and answer the questions that follow: [4]
Proteins are the most abundant biomolecules of the living system. Proteins are the polymers of about twenty
different α-amino acids which are linked by peptide bonds. Ten amino acids are called essential amino acids. In

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 zwitter ionic form, amino acids show amphoteric behaviour as they react both with acids and bases.
On the basis of their molecular shape, proteins are classified into two types: Fibrous and Globular proteins.
Structure and shape of proteins can be studied at four different levels i.e., primary, secondary, tertiary and
quaternary, each level being more complex than the previous one. The secondary or tertiary structure of proteins
get disturbed on change of pH or temperature and they are not able to perform their functions. This is called
denaturation of proteins.
Answer the following questions:
a. What are essential amino acids? (1)
b. What is meant by zwitter ionic form of amino acids? (1)
c. i. Give one example each for Fibrous protein and Globular protein.
ii. What type of linkages hold monomers of proteins together? (2× 1 = 2)
OR
c. i. What is the structural feature which characterises a reducing sugar?
ii. What is the structural difference between nucleoside and nucleotide? (2× 1 = 2)
65. Read the following text carefully and answer the questions that follow: [4]
Living system are made up of complex molecules called Biomolecules. Carbohydrate, proteins, enzymes,
nucleic acids, lipids, hormones ATP, DNA and RNA play an important role in our daily life. Carbohydrates
provide us energy. Protein help in growth and maintenance of body. Nucleic acids, RNA helps in protein
synthesis, DNA helps in transfer of genetic characteristics. Fat are source of energy and protect our vital organs.
i. Why are carbohydrates optically active? (1)
ii. Name two acidic amino acids. (1)
iii. Name a protein which has quarternary structure. (2)
OR
What are products of hydrolysis of fats? (2)
Section D
66. Write the reactions of D-glucose which can’t be explained by its open-chain structure. How can the cyclic [5]
structure of glucose explain these reactions?
67. What is the basic structural difference between starch and cellulose? [5]
68. On the basis of which evidences D-glucose was assigned the following structure? [5]
CHO
|

( CHOH)
|
4

CH2 OH

69. Write the structures of fragments produced on the complete hydrolysis of DNA. How are they linked in DNA [5]
molecule? Draw a diagram to show the pairing of nucleotide bases in the double helix of DNA.
70. Write the important structural and functional differences between DNA and RNA. [5]

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