Previous Years' CBSE Board Questions

14.1 Carbohydrates 12. Write the product obtained when D-glucose

reacts with H,NOH. (AI 2015)
VSA (1 mark) 13. Which one of the following is a
1. Name the disaccharide which on hydrolysis monosaccharide:
gives two molecules of glucose. starch, maltose, fructose, cellulose
(One word, 2020) (Foreign 2015)
2. Write the name of linkage joining two 14. Which of the two components of starch is
monosaccharides. (One word, 2020) water soluble? (Dellhi 2014)
3. a-D(+) glucose and ß-D(+) glucose are 15. Write the product formed on reaction of
(a) geometrical isomers D-glucose with Br, water. (Delli 2014)
(b) enantiomers 16. Write the product formed when glucose is
(c) anomers treated with HI. (Dellhi 2014)
(d) optical isomers (2020) 17. Define the following term:
4. Assertion (A) : Sucrose is a non-reducing Anomers (AT2014, Foreign 2014)
sugar. 18. Define the following term :
Reason (R) : Sucrose has glycosidic linkage. Polysaccharides (Foreign 2014)
(a) Both Assertion (A) and Reason (R) 19. Define the following term : Invert sugar
are correct statements, and Reason (Foreign 2014)
(R) is the correct explanation of the 20. What is a glycosidic linkage? (Dellhi 2013
Assertion (A).
(b) Both Assertion (A) and Reason (R) 21. Name two components of starch.
are correct statements, but Reason (R) (Delhi 20130
is not the correct explanation of the 22. Write a reaction which shows that all the
Assertion (A). carbon atoms in glucose are linked in a
(c) Assertion (A) is correct, but Reason (R) straight chain. (AI 2012)
is incorrect statement.
23. State two functions of carbohydrates.
(d) Assertion (A) is incorrect, but Reason (AI 2012C)
(R) is correct statement. (2020)
5. What is the basic structural difference
24. Explain what is meant by the following:
Pyranose structure of glucose?
between glucose and fructose? (Delli 2019) (AI, Foreign 2011)
6 Write the products obtained after hydrolysis SA (2 marks)
of lactose. (Delli 2019)
25. Define the following terms :
7. Define the following with an example of: () Oligosaccharides
Polysaccharides (1/3, 2018) (ii) Invert sugar (2020)
8 Write the product when D-glucose reacts with 26. Write the reactions showing the presence of
conc. HNO,. (1/3, 2018, Al 2012)
9. Write the name of two monosaccharides
following in the open structure of glucose :
() an aldehyde group
obtained on hydrolysis of lactose sugar. (0) a primary alcohoi (2020)
(Delhi 2016)
10. Write the structural difference between
27. Enumerate the reactions of glucose which
starch and cellulose.
cannot be explained by its open chain
(AI 2016) structures. (Delhi 2014C, AI 2011)
11. Which one of the following is a disaccharide: 28. Write any two reactions of glucose which
Starch, Maltose, Fructose, Glucose? cannot be explained by the open chain
(Dellhi 2015) structure of glucose molecule. (Delli 2012)
29. Write down the structures and names of 39. What is the difference between fibrous
the products formed when D-glucose is protein and globular protein?
treated with (i) Hydroxylamine (i) Acetic (1/3, AI, 2017C, Dellhi 2015)
anhydride. (AI 2012C)
40. Give one example each for fibrous protein
30. Write down the structures and names of and globular protein.
the products formed when D-glucose is (AI 2016, Dellhi 2014, AI 2013C)
treated with
(i) Bromine water 41. Amino acids show amphoteric behaviour.
Why? (AI 2015)
(i) Hydrogen iodide (Prolonged heating).
(AI 2012C) 42. What is the difference between acidic anmino
31. What is essentially the difference bctween acids and basic amino acids? (Foreign 2015)
a-form and ß-form of glucose? Explain. 43. What type of linkage is responsible for the
(Delhi 2011) formation of proteins? (Dellhi, Foreign 2014)
LAI (3 marks) 44. Define the following term :
Essential amino acids (AI 2014)
32. Give the plausible explanation for the
following : 45. Define the following term:
(a) Glucose doesn't give 2,4-DNP test. Denaturation of proteins (Foreign 2014)
(b) The two strands in DNA are not 46. Define the following term:
identical but are complementary. Amino acids (Foreign 2014)
(c) Starch and cellulose both contain
glucose unit as monomer, yet they are 47. Define a 'peptide linkage.
structurally different. (2020) (AI 2014C, 2011, Foreign 2011)
33. Write chemical reactions to show that open 48. Where does the water present in the egg go
structure of D-glucose contains the following: after boiling the egg? (Delhi 2012C)
(i) Straight chain SA (2 marks)
(iü) Five alcohol groups 49. Define the following with an example of
(ii) Aldehyde as carbonyl group. (Delhi 2019) each:
34. What happens when D-glucose is treated (i) Denatured protein
with the following reagents? (ii) Essential amino acids (2/3, 2018)
(a) Br, water
(b) HCN 50. (a) Amino acids show amphoteric behaviour.
(c) (CH,CO),0 (AI 2019) Why?
35. Define the following terms : (b) Write one difference between a-helix and
(i) Glycosidic linkage B-pleated structures of proteins.
(ii) Invert sugar (2/3, 2018)
(i) Oligosaccharides (AI2014) 51. Describe what you understand by primary
36. What is essentially the difference between structure and secondary structure of
a-glucose and B-glucose? What is meant by proteins? (Delli 2011, Foreign 2011)
pyranose structure of glucose? (AI 2012) 52. Explain what is meant by a peptide linkage.
37. Mention the structural feature characterising (Deli 2011)
reducing sugar. (Delli 201 1C)
LAI (3 marks)
14.2 Proteins
53. Differentiate between the following:
VSA (1 mark) (1) Amylose and Amylopectin
38. Peptide linkage is present in (ii) Peptide linkage and Glycosidic linkage
(a) carbohydrates (b) vitamins (ii) Fibrous proteins and Globular proteins.
(c) protcin (d) rubber. (2020) (Dellhi 2019)
54. Define the following terms as related to 69. Name the only vitamin which can be
proteins : synthesized in our body. Name the disease
() Peptide linkage caused due to the deficiency of this vitamin.
(ii) Primary structure (Delhi 2013C)
(ii) Denaturation (AI 2015, 2014) 70. How are hormones and vitamins different in
55. What are essential and non-essential amino respect of their source and functions?
acids? Give two examples of each. (AI 2013C)
(AI 2014C, Delhi 2012C) 71. Name the deficiency disease resulting from
56. (a) Give two differences between globular lack of vitamin A in the diet. (Delhi 2011C)
and fibrous proteins. 72. The deficiency of which vitamin causes the
(b) What change occurs in the nature of egg disease, 'pernicious anaemia"? (AI 2011C)
protein on boiling? (Dellhi 2013C)
LAI (3 marks)
14.3 Enzymes 73. How are vitamins classified? Name the
VSA (1 mark) vitamin responsible for the coagulation of
blood. (Delhi 2015C)
57. Define the following term:
Enzymes (Foreign 2014, Al 2014 C) 14.5 Nucleic Acids
58. What is meant by biocatalysts? (Delli 2012) VSA (1 mark)
74. What is difference between a nucleoside and
14.4 Vitamins nucleotide? (Delli 2016, 2014C)
VSA (1 mark) 75. What type of linkage is present in nucleic
acids? (AI 2016
59, Why vitamin Ccannot be stored in our
body? (Dellhi 2016) 76. Namne of the base that is found in nucleotid
of RNA only. (Delli 201
60. Write the name of vitamin whose deficiency
causes bone deformities in children. 77. Deine the following term:
Nucleoside (Foregin 2014)
(Delli 2015)
61. Write the name of the vitamin whose 78. Mention one important function of nucleic
deficiency causes bleeding of gums. acids in our body. (AI 2013C)
(Foreign 2015) SA (2 marks)
62. Deficiency of which vitamin causes night 79. Writethe structural and functional difference
blindness? (Delhi 2014) between DNA and RNA. (Delhi 2013C)
63. Deficiency of which vitamin causes rickets? 80. Write the main structural difference between
(Dellhi 2014) DNA and RNA. Of the two bases, thymine
64. Deficiency of which vitamin causes scurvy? and uracil, which one is present in DNA?
(Delli 2014) (Delli 2012)
65. Define the following term: 81. Name the bases present in RNA. Which one
Vitamins (Foregin 2014) of these is not present in DNA? (Dellhi 2011)
82. Write the main structural difference between
66. Why are vitamin A and vitamin C essential
for us? (Dellhi 2014C) DNA and RNA. Of the four bases, name
those which are common to both DNA and
67. Name the deficiency diseases resulting from RNA. (AI2011)
lack of vitamins A and E in the diet.
(Delhi 2013C) LAI (3 marks)
68. Name one of the water soluble vitamin which 83. What are the different types of RNA found
is powerful antioxidant. Give its one natural in cells of organisms? State the functions of
Source. (Dellhi 2013C, AI 2012C) each type. (Delhi 2012C)
 Detailed Solutions

1. Maltose glucose units. In starch, there is a-D-glycosidic

Glycosidic linkage. linkage. Both the components of starch-amylose
3. (c) :The pair of stereoisomers which differ and amylopectin are polymer of a-D-glucose.
only in the configuration of the hydroxyl group at On the other hand, cellulose is a linear polymer
C, are called anomers. of B-D-glucose in which C of one glucose
unit is connected to C, of the other through
H-C-OH HO C-H B-D-glycosidic linkage.
H2 -OH H OH
11. Maltose is a disaccharide as it consists of two
a-D-glucose units.
HO -H HO -H 12. D-Glucose reacts with H,N-OH to give
H H
glucose oxime.
-OH OH CHO CH=N-OH
H (CHOH), +NH,OH (CHOH),
CH,OH CH,OH CH,OH CH,OH
-D-(+) Glucose B-D-(+) Glucose 13. Fructose is a monosaccharide because it
4. (a) : Sucrose is disaccharide and its two
cannot be hydrolysed to simpler polyhydroxy
nonosaccharides are held together by aglycosidic aldehydes or ketones.
linkage. Since the reducing groups of glucose 14. Amylose is water soluble and amylopectin is
and fructose are involved in glycosidic bond insoluble in water.
formation, therefore, sucrose is a non-reducing
sugar.
15. D-Glucose gets oxidised to carboxylic acid
(gluconic acid) on reaction with bromine water.
5. Glucose contains an aldehydic group while ÇHO COOH
fructose contains a ketonic group. Br,-water.
6. Lactose on hydrolysis gives B-D-glucose and (CHOH), (CHOH),
CH,OH CH,OH
B-D-galactose. D-Glucose Gluconic acid
7. Carbohydrates which yield a large number 16. On prolonged heating with HL, D-glucose
of monosaccharide units on hydrolysis are called forms n-hexane.
polysaccharides, e.g., cellulose. CHO
8. On oxidation with nitric acid, D-glucose
yields saccharic acid. (CHO), CH,-(CH,),CH,
n-Hexane
CHO COOH CH,OH
D-Glucose
conc. HNO, . (CHOH),
(CHOH), 17. Refer to answer 3.
CH,OH COOH 18. Refer to answer 7.
D-glucose D-saccharic acid
19. An equimolar mixture of glucose and
9. Refer to answer 6. fructose, obtained by hydrolysis of sucrose in
10. The basic structural difference between presence of an acid or the enzyme invertase is
starch and cellulose is of linkage between the called invert sugar.
20. The two monosaccharides are joined present in glucose. This indicates presence of
together by an oxide linkage formed by the loss of aldehyde group.
water molecule. Such linkage is called glycosidic CHO COOH
linkage.
CH,OH (CHOH), +(o) (CHOH),
H o H CH,OH CH,OH
K OH Gluconic acid

OH (i) On acetylation with acetic anhydride, glucose

H OH gives a pentaacetate. This confirms that glucose
HOH,C contains five - OH groups.
CHO
H OH/
H
OH H CH,OH (ÇHO), +S(CH,CO),0 ’
H,OH
21. Amylose and amylopectin are the two Glucose
components of starch.
22. Glucose when heated with red P and HI gives
n-hexane. (CH-0--CH),
+5CH,COOH
c,H,0, Red PHy
A CH,CH,CHCH,CH,CH,
n-Hexane

It indicates the presence of straight chain of six Glucose pentaacetate

carbon atoms in glucose. 27. The following reactions of D-glucose cannot
23. (i) Carbohydrates act as storage molecules be explained on the basis of its open chain
as starch in plants and glycogen in animals. structure:
(ii) They act as constituent of cell membrane. (i) D-Glucose does not react with sodium
bisulphite (NalHSO,).
24. The six membered cyclic structure of glucose (i) It does not give 2, 4-DNP test and Schiff's test.
is called pyranose structure (a- orB-), in analogy (iii) The pentaacetate of D-glucose does not react
with heterocyclic compound pyran. with hydroxylamine.
CH,OH (iv) D-Glucose shows the phenomenon of
mutarotation i.e., when its aqueous solution is
HO OH HOH kept for sometime its optical activity changes.
(v) On reaction with Imole of methanol, it yield
H OH
a-D-(+)-Glucopyranose two monomethyl derivatives which are known as
methyla-D-glucosideand methyl-B-D-glucoside.
25. (i) These are the carbohydrates which on 28. Refer to answer 27.
hydrolysis give 2 10 monosaccharides. For
29. (i) Refer to answer 12.
example, sucrose, lactose, maltose, etc. CHO
(ii) Refer to answer 19. CHO
26. (i) Glucose on oxidation with a mild (i (CHOH), O, (CHO--CH),
oxidising agent like bromine water gives gluconic CH,OH
acid containing the same six carbon atoms as Glucose pentaacetate
30. (i) Refer to answer 15. linkage. Both the components of starch-amylose
(ii) Refer to answer 16. and amylopectin are polymers of c-D-glucose.
31. In -D Glucose, the -OH group at C On the other hand, cellulose is a linear polymer
is towards right whereas in B-glucose, the of B-D-glucose in which C1 of one glucose
-OH group at C, is towards left. Such a pair of unit is connected to C4 of the other through
stereoisomers which differ in the configuration B-D-glycosidic linkage.
only at C, are called anomers.
33. (i) Refer to answer 22.
(ii) Refer to answer 26(i).
HC-oH HOC -H
(ii) Refer to answer 26(i).
HC-OH HOH 34. (a) Refer to answer 15.
HOC-H HOC-H
CHO HN
OH
Hc oH HC- OH HCN

H¢ H
(b) (HOH), (ÇHOH),
H,OH CH,OH
"CH,OH
-D-(+) -Glucose
CH,OH
B-D-(}-Glucose
Glucose cyanohydrin
(c) Refer to answer 26(i).
32. (a) Actually, glucose exists in the cyclic
35. (i) Refer to answer 20.
hemiacetal form with only a small amount
(< 0.05%) of the open chain form. Since, the (iü) Refer to answer 19.
concentration of the open chain form is low and (iii) Refer to answer 25().
its reaction with 2,4-DNP is reversible, therefore, 36. Refer to answers 31 and 24.
formation of 2,4-DNP derivative cannot disturb
37. The sugars which reduce Fehling's solution
the equilibrium to regenerate more of the open and Tollens' reagent are called reducing sugars.
chain form from the cyclic hemiacetal form and
For example, all monosaccharides containing free
hence, does not give this test.
(b) The two strands in DNA molecule are held -CHO Or -=0group are reducing sugars.
together by the hydrogen bonds between purine 38. (c) Peptide linkage is present in proteins.
base of one strand and pyrimidine base of the
other and vice versa. Because of different sizes and 39. Characteristic diferences between globular
geometries of the bases, the only possible pairing and fibrous proteins can be given as :
in DNA are G(guanine) and C(cytosine) through S. Globular proteins Fibrous proteins
three H-bonds, i.e., (C G) and between A No.

(adenine) and T (thymine) through two H-bonds 1.These are cross- These are linear
(i.e, A = T) . Due to this base-pairing principle, linked proteins and condensation
are condensation polymer.
the sequence of bases in one strand automatically
product of acidic
fixes the sequence of bases in the other strand. and basic amino
Thus, the two strands are complementary and not acids.
identical. 2 These are soluble in These are insoluble
(c) The basic structural difference between water, mineral acids in water butsoluble
starch and cellulose is of linkage between the and bases. in strong acids and
bases.
glucose units. In starch, there is c-D-glycosidic
 3. These proteins haveThese are linear
three dimensionalpolymers held
folded structure.together by
R R
These are stabilised intermolecular Peptide linkage
by internal hydrogen bonds, 48. An egg contains a soluble globular protein
hydrogen bonding. e.g, hair, silk. called albumin which is present in the white
eg-s cgg albumin,
enzymes. part. On boiling, denaturation (loss of biological
activity) of this protein takes place which results
40. Globular protein - Insulin in the formation of insoluble fibrous proteins. The
Fibrous protein - Keratin water molecules are utilized in this process.
41. As amino acids have both acidic (carboxyl 49. (i) Refer to answer 45.
group) and basic groups (amino group) in the (ii) Refer to answer 44.
same molecule, they react with both acids and 50. (a) Refer to answer 41.
bases. Hence, they show amphoteric behaviour. (b) In -helix structure, intramolecular H-bonding
42. Acidic amino acids are those which contain takes place whereas in B-pleated structure, inter
more number of carboxyl groups as compared molecular H-bonding takes place.
to amino groups whereas basic anmino acids are 51. Primary structure : The specific sequence in
those which contains more number of amino which the various amino acids present in aprotein
groups than carboxyl groups. are linked to one another is called its primary
43. Peptide linkage. structure. Any change in the primary structur
44. Essential amino acids : Amino acids which creates a different protein.
Secondary structure: The conformation
cannot be synthesized in the body and must be
the polypeptide chain is known as secondary
obtained through diet are known as essential structure. The two types of secondary structure
amino acids, e.g., valine, leucine, etc. are o-helix and B-pleated sheet structure.
45. Denaturation : The loss of biological activity In a-helix structure, the polypeptide chain forms
of a protein by changing the pH, temperature all the possible hydrogen bonds by twisting into a
or by adding some salt due to disruption of the right handed screw (helix) with the -NH groups
native structure of protein is called denaturation. of each amino acid residue hydrogen bonded to
During denaturation, secondary and tertiary the C=0 group of an adjacent turn of the helix.
structure of protein is destroyed but primary In B-pleated sheet structure, all peptide chains are
structure remains intact.
stretched out to nearly maximum extension and
46. Organic compounds containing both amino then laid side by side which are held together by
(-NH) and carboxyl (COOH) functional intermolecular hydrogen bonds.
groups are called amino acids. 52. Refer to answer 47.
R-CH-COOH 53. (i) Amylose is a linear condensation polymer
of a-D-glucose in which C, of one glucose unit is
47. Proteins are the polymers of a-amino acids attached to C, of the other through a-glycosidic
linked by amide formation between carboxyl and linkage while amylopectin is a highly branched
amino group. This is called peptide linkage or polymer in which C, of terminal glucose unit in
peptide bond, e.g. each chain is further linked to Cof some other
glucose unit in the next chain through C,-C growth and health of the organism are called
-glycosidic linkage. vitamins.
(i) Peptide linkage is an amide linkage formed 66. The deficiency of vitamin A leads to
between -COOH group of one d-amino acid and xerophthalmia and night blindness. The deficiency
-NH, group of the other amino acid by loss of a of vitamin C leads to scurvy.
molecule of water whereas a linkage between two 67. Vitamin - A: Night blindness
monosaccharides units through oxygen atom is Vitamin E: Muscular weakness.
called glycosidic linkage. 68. Vitamin C is water soluble and powerful
(iii) Refer to answer 39. antioxidant. Natural source of vitamin C is amla.
54. (i) Refer to answer 47. 69. Vitamin D
(ii) Refer to answer 51.
Disease caused due to deficiency of Vitamin D is
(i) Refer to answer 45. rickets.
55. Amino acids which cannot be synthesised 70.
in the body and must be obtained through diet Hormones Vitamins
are known as essential amino acids, e.g, valine (i) The biomolecules These are essential
and leucine. There are ten essential amino acids. which transfer dietary factors
Amino acids which can be synthesised in the information from one required by an
body are known as non-essential amino acids, e.g, group of cell to distant organism in minute
alanine and glutamic acids. tissue or organ. quantities.

56. (a) Refer to answer 39. |() They are produced in They are supplied to
the body in ductless|the body from thel
(b) Protein is denatured and its biological activity glands. food eaten.
Slost.
71. Refer to answer 67.
57. Most of the chemical reactions which occur 72. Vitamin B
in living systems process at very slow rates under 73. Vitamins are classified into two groups
mild condition of temperature and pH. These
reactions are catalysed by a group of biomolecules depending upon their solubility in water or fat.
called enzymes. () Fat soluble vitamins, (e.g, vitamin Aand D)
58. Substances which catalyse chemical
(ii) Water soluble vitamins, (e.g, vitamin B and
C) vitamin K is responsible for the coagulation of
reactions taking place in living organisms are blood.
called biocatalysts, e.g., enzymes.
74. Nucleoside contains pentose sugar, and base
59. Vitamin C is soluble in water and regularly whereas nucleotide contains pentose sugar, base
excreted in urine and hence cannot be stored in
as well as phosphate group.
body. Nucleoside = Base + Sugar
60. Vitamin D Nucleotide - Base + Sugar + Phosphate
61. Vitamin C 75. Ester linkage
62. Vitamin A 76. Uracil
63. Vitamin D 77. Refer to answer 74.
64. Vitamin C 78. DNA is reserve of genetic information and
65. Organic compounds required in the diet responsible for heredityy transmission.
in small amounts to perform specific biological 79. Structural ditferences between DNA and
functions for normal maintenance of optimum RNA
(i) The sugar in DNA is deoxyribose while that 82. Refer to answer 79.
in RNA is ribose. Common bases in DNA and RNA are adenine,
(ii) DNA has a double-stranded helical structure, guanine and cytosine.
while RNA has a single-stranded helical structure. 83. RNA are of three types :
Functional differences between DNA and RNA (i) Messenger RNA (m-RNA): Function as
(i) DNA is the chemical basis of heredity and messenger carrying the information in a gene to
is responsible for maintaining the identity of the protein synthesizing machinery.
ditferent species. (i) Transfer RNA (-RNA) : They transfer the
(i) RNA molecules are responsible for protein amino acids from cytoplasm to the protein
synthesis but the message for the synthesis of a synthesizing machinery.
particular protein is present in DNA. (iii) Ribosomal RNA (r-RNA) : They associates
with a set of proteins to form ribosomes. These
80. Refer to answer 79. complex structures, which physically move among
In DNA, thymine is present. an m-RNA molecule, catalyze the assembly of
81. The bases present in RNA are adenine (A), amino acids into protein chains. They also bind
guanine (G) cytosine (C) and Uracil (U). t-RNAs and various molecules necessary for
Uracil is not present in DNA. protein synthesis.