NEET - BIOMOLECULES MODEL - 2024

1. On hydrolysis of starch, we finally get
(a) Glucose
(b) Fructose
(c) Both (a) and (b)
(d) Surcose

2. The couplings between base units of DNA is through:
(a) Hydrogen bonding
(b) Electrostatic bonding
(c) Covalent bonding
(d) Vander Waals forces

3. Enzymes take part in a reaction and
(a) decrease the rate of a chemical reaction
(b) increase the rate of a chemical reaction
(c) both a and b
(d) none of the above

4. Chemically considering digestion is basically
(a) Anabolism
(b) Hydrogenation
(c) Hydrolysis
(d) Dehydrogenation

5. The alpha-D glucose and beta-D glucose differ from each other due to difference in carbon atom with respect to its
(a) conformation
(b) configuration
(c) number of OHgroups
(d) size of hemiacetal ring

6. Which of the following protein destroy the antigen when it enters in body cell?
(a) antibodies
(b) insulin
(c) chromoprotein
(d) phosphoprotein

7. In reference to biological role, Ca2+ ions are important in
(a) triggering the contraction of muscles
(b) generating right electrical potential across cell membrane
(c) hydrolysis of ATP
(d) defence mechanism

8. Sucrose in water is dextro-rotatory , [a]_D = + 66.4⁰ . When boiled with dilute HCl, the solution becomes leavo – rotatory , [a]_D = -20⁰ . In this process the sucrose olecules breaks into
(a) L-glucose + D-fructose
(b) L-glucose + L-fructose
(c) D-glucose + D-fructose
(d) D-glucose + L-fructose

9. Areagent suitable for the determination of Nterminal residue of a peptide is
(a) p-toluenesulphonylchloride
(b) 2, 4-dinitrophenylhydrazine
(c) carboxypeptidase
(d) 2, 4-dinitrofluorobenzene

10. The reactions of
(a) oxygen and
(b) carbon monoxide with haeme (the prosthetic group of haemoglobin) give
(c) only oxygen-haeme complex
(d) only carbon monoxide-haeme complex

11. Identify an element amongst the following which is responsible for oxidation of water to O2 in biological processes
(a) Fe
(b) Mn
(c) Mo
(d) Cu

13. The number of molecules of ATP produced in the lipid metabolism of a molecule of palmitic acid is
(a) 130
(b) 36
(c) 56
(d) 86

14. In DNA the complementary bases are
(a) adenine and thymine; guanine and cytosine
(b) uracil and adenine; cytosine and guanine
(c) adenine and guanine; thymine and cytosine
(d) adenine and thymine; guanine and uracil

15. Glucose molecule reacts with ‘X’ number of molecules of phenylhydrazine to yield osazone. The value of ‘X’ is
(a) four
(b) one
(c) two
(d) three

16. Which of the following is the sweetest sugar?
(a) Sucrose
(b) Glucose
(c) Fructose
(d) Maltose

17. In cells the net production of ATPmolecules generated from one glucose molecule is
(a) 46
(b) 32
(c) 36
(d) 40

18. Which of the following is a steroid hormone?
(a) Cholesterol
(b) Adrenaline
(c) Thyroxine
(d) Progesterone

19. The dominant cation in the blood plasma (extracellular fluid) is
(a) potassium
(b) calcium
(c) magnesium
(d) sodium

20. The number of essential amino acids in man is
(a) 8
(b) 10
(c) 18
(d) 20

21. Mg is present in which of the following :
(a) Starch
(b) Chlorophyll
(c) Both
(d) None

22. Which of the following gives positive Fehling solution test?
(a) Protein
(b) Sucrose
(c) Glucose
(d) Fats

23. For

Which statement is incorrect about peptide bond ?
(a) C— N bond length in proteins is longer than usual bond length of the C— N bond
(b) Spectroscopic analysis shows planar structure of the — NH— O— C group
(c) C— N bond length in proteins is smaller than usual bond length of the C—N bond
(d) None of the above

24. Which is correct statement?
(a) Starch is a polymer of D-glucose
(b) In cyclic structure of fructose, there are four carbons and one oxygen atom
(c) Amylose is a component of cellulose
(d) Proteins are composed of only one type of amino acids

25. Which of the following is correct about H bonding in nucleotide?
(a) A – A and T – T
(b) G – T and A – C
(c) A – G and T – C
(d) A – T and G – C

26. Cellulose is a polymer of
(a) Glucose
(b) Fructose
(c) Ribose
(d) Sucrose

27. Enzymes are made up of
(a) Edible proteins
(b) Proteins with specific structure
(c) Nitrogen containing carbohydrates
(d) Carbohydrates

28. Which is not a true statement?
(a) alpha-Carbon of alpha-amino acid is asymmetric
(b) All proteins are found in L-form
(c) Human body can synthesize all proteins they need
(d) At pH= 7 both amino and carboxylic groups exist in ionised form

29. Glycolysis is
(a) conversion of glucose to haem
(b) oxidation of glucose to glutamate
(c) conversion of pyruvate to citrate
(d) oxidation of glucose to pyruvate

30. Phospholipids are esters of glycerol with
(a) Three phosphate groups
(b) Three carboxylic acid residues
(c) Two carboxylic acid residues and one phosphate group
(d) One carboxylic acid residue and two phosphate groups

31. Chargaff’s rule states that in an organism
(a) Amounts of all bases are equal
(b) Amount of adenine is equal to that of thymine and the amount of guanine is equal to that of cytosine
(c) Amount of adenine is equal to that of guanine and the amount of thymine is equal to that of cytosine
(d) Amount of adenine is equal to that of cytosine and rthe amount of thymine is equal to that of guanine

32. Which one of the following structures represents the peptide chain?

33. Asequence of how many nucleotides in messenger RNAmakes a codon for an amino acid?
(a) Three
(b) Four
(c) One
(d) Two

34. The hormone that helps in the conversion of glucose to glycogen is
(a) Cortisone
(b) Bile acids
(c) Adrenaline
(d) Insulin

35. The enzyme which hydrolyses triglycerides to fatty acids and glycerol is called
(a) Maltase
(b) Lipase
(c) Zymase
(d) Pepsin

36. The correct statement in respect of protein haemoglobin is that it
(a) functions as a catalyst for biological reactions
(b) maintains blood sugar level
(c) acts as an oxygen carrier in the blood
(d) forms antibodies and offers resistance to dieases

37. The helical structure of protein is stabilized by
(a) dipeptide bonds
(b) hydrogen bonds
(c) ether bonds
(d) peptide bonds

38. Which functional group participates in disulphide bond formation in proteins?
(a) Thioester
(b) Thioether
(c) Thiol
(d) Thiolactone

39. The cell membranes are mainly composed of
(a) fats
(b) proteins
(c) phospholipids
(d) carbohydrates

40. Which one of the following is a peptide hormone?
(a) Testosterone
(b) Thyroxin
(c) Adrenaline
(d) Glucagon

41. The human body does not produce
(a) Vitamins
(b) Hormones
(c) Enzymes
(d) DNA

42. During the process sof digestion, the proteins present in food materials are hydrolysed to amino acids. The two enzymes involved in the process Proteins Polypeptides Amino acids are respectively.
(a) Diastase and Lipase
(b) Pepsin and Trypsin
(c) Invertase and Zymase
(d) Amylase and Maltase

43. RNA and DNA are chiral molecules, their chirality is due to
(a) chiral bases
(b) chiral phosphate ester units
(c) D-sugar component
(d) L-sugar component.

44. Which one of the following is an amine hormone?
(a) Thyroxine
(b) Oxypurin
(c) Insulin
(d) Progesterone

45. In DNA, the complimentary bases are:
(a) Adenine and thymine; guanine and cytosine
(b) Adenine and thymine; guanine and uracil
(c) Adenine and guanine; thymine and cytosine
(d) Uracil and adenine; cytosine and guanine

46. The segment of DNAwhich acts as the instrumental manual for the synthesis of the protein is:
(a) ribose
(b) gene
(c) nucleoside
(d) nucleotide

47. Which of the following hormones contains iodine?
(a) Testosterone
(b) Adrenaline
(c) Thyroxine
(d) Insulin

48. Which one of the following does not exhibit the phenomenon of mutarotation?
(a) (+) – Sucrose
(b) (+) – Lactose
(c) (+) – Maltose
(d) (–) – Fructose

49. Fructose reduces Tollen’s reagent due to:
(a) enolisation of fructose followed by conversion to glucose (having aldehydic group) by the base present in Tollen’s reagent
(b) asymmetric carbons
(c) primary alcoholic group
(d) secondary alcoholic group

50. Which one of the following statements is not true regarding (+) Lactose?
(a) On hydrolysis (+) Lactose gives equal amount of D(+) glucose and D(+) galactose.
(b) (+) Lactose is a E-glycoside formed by the union of a molecule of D(+) glucose and a molecule of D(+) galactose.
(c) (+) Lactose is a reducing sugar and does not exhibit mutarotation.
(d) (+) Lactose, C₂H22O11 contains 8- OHgroups.

51. Which of the statements about “Denaturation” given below are correct?

(a) Denaturation of proteins causes loss of secondary and tertiary structures of the protein.
(b) Denturation leads to the conversion of double strand of DNAinto single strand
(c) Denaturation affects primary strucrture which gets distorted
(d) During denaturation secondary and tertiary structures of protein destroyed but primary structures remains intact.

52. Which one of the following, statements is incorrect about enzyme catalysis?
(a) Enzymes are mostly proteinous in nature.
(b) Enzyme action is specific.
(c) Enzymes are denaturated by ultraviolet rays and at high temperature.
(d) Enzymes are least reactive at optimum temperature.

53. Deficiency of vitamin B1 causes the disease
(a) Convulsions
(b) Beri-Beri
(c) Cheilosis
(d) Sterility

54. Which one of the following sets of monosaccharides forms sucrose?
(a) a -D –Galactopyranose and a -D – Glucopyranose

(b) a -D –Galactopyranose and      b – D -Fructofuranose
(c) b -D –Galactopyranose and       a – D -Fructofuranose
(d) a -D –Galactopyranose and      b – D –Fructopyranose

55. In DNAthe linkages between different nitrogenous bases are:
(a) peptide linkage
(b) phosphate linkage
(c) H-bonding
(d) glycosidic linkage

56. Which one of the following pairs is not correctly matched?

(a) Triose sugar – DHAP

(b) Starch – amylase and amyloprectin

(d) Cortisone – sterols

57. If one strand of DNA has the sequence ATGCTTGA, the sequence in the complementary strand would be:

(a) TCCGAAT

(b) TACGTACT

(d) TAGCTAGT

58. The central dogma of molecular genetics states that the genetic information flows from

(a) Amino acids → Proteins → DNA

(b) DNA → Carbohydrates → Proteins

(d) DNA → RNA → Carbohydrates

59. The correct statement regarding RNA and DNA, respectively is

(a) the sugar component in RNA is a arabinose and the sugar component in DNA is ribose

(b) the sugar component in RNA is 2′-deoxyribose and the sugar component in DNA is arabinose

(d) the sugar component in RNA is arabinose and the sugar component in DNA is 2′-deoxyibose

60. The pair in which both species have iron is

(a) Haemocyanin, nitrogenase

(b) Haemoglobin, cytochromes

(d) Carboxypeptidase, haemoglobin

61. Which one given below is a non-reducing sugar?

(a) Sucrose

(b) Maltose

(d) Glucose

62. Which one of the following pairs is correctly matched?

(a) Fats→Long saturated Fatty acidss chain

(b) Glycogen →Forms the plant cell wall

(d) Deoxyribose →RNA.

63. Which of the following hormones is produced under the conditions of stress which stimulate glycogenolysis in the liver of human beings?

(a) Thyroxin

(b) Estradiol

(d) Adrenaline

64. Which of the statements about “Denaturation” given below are correct?

(1) Denaturation of proteins causes loss of secondary and tertiary structures of the protein.

(2) Denaturation leads to the conversion of double strand of DNA into single strand

(3) Denaturation affects primary structure which gets distorted

(a) (2) and (3)

(b) (1),(2) and (3)

(d) (1) and (2)

65. Fructose reduces Tollens’ reagent due to

(a) asymmetric carbons

(b) enolisation of fructose followed by conversion to aldehyde by bas

(d) secondary alcoholic group

66. In a polysaccharide, the individual monosaccharides are linked by a……

(a) Ester bond

(b) Phosphodiester bond

(d) Peptide bond

67. RNA and DNA are chiral molecules, their chirality is due to

(a) chiral bases

(b) D-sugar component

(d) Z-sugar component

68. During the process of digestion, the proteins present in food materials are hydrolysed to amino acids. The two enzymes involved in the process proteins polypeptides amino acids, are respectively

(a) invertase and zymase

(b) diastase and lipase

(d) pepsin and trypsin.

69. Which one of the following statements is correct?

(a) All amino acids except lysine are optically active

(b) All amino acids are optically active

(d) All amino acids except glutamic acids are optically active

70. The cell membranes are mainly composed of

(a) fats

(b) carbohydrates

(d) phospholipids

71. The correct statement in respect of protein haemoglobin is that it

(a) functions as a catalyst for biological reactions

(b) forms antibodies and offers resistance to diseases

(d) acts as an oxygen carrier in the blood

72. Glycolysis is

(a) oxidation of glucose to glutamate

(b) conversion of pyruvate to citrate

(d) conversion of glucose to haem

73. Enzymes are made up of

(a) nitrogen containing carbohydrates

(b) carbohydrates

(d) proteins with specific structure

74. The hormone that helps in the conservation of glucose to glycogen is

(a)Cortisone

(b)Bile acids

(c)Adrenaline

(d)insulin

75. In a protein molecule various amino acids are linked together by

(a) peptide bond

(b) dative bond

(d) β – glycosidic bond

76. Which of the following statements is not correct

(a) Ovalbumin is a simple food reserve in egg-white

(b) Blood proteins thrombin and fibrinogen are involved in blood clotting

(d) Insulin maintanis sugar level in the blood of a human body

77. The difference between amylose and amylopectin is

(a) Amylopectin have 1 4 -linkage and 1 6 -linkage

(b) Amylose have 1 → 4 -linkage and 1 6 -linkage

(d) Amylopectin have 1 4 -linkage and 1 6 -linkage

78. Which of the following compounds can form a zwitterion?

(a) Aniline

(b) Acetanilide

(d) Benzoic acid

79. The non-essential amino acid among the following is:

(a) valine

(b) leucine

(d) lysine

80. Among the following, the reaction that proceeds through an electrophilic substitution, is:

81. Which of the following is a basic amino acid ?

(a) Tyrosine

(b) Lysine

(d) Alanine

82. An organic compound contains 78% (by wt.) carbon and remaining percentage of hydrogen. The right option for the empirical formula of this compound

is : [Atomic wt. of C is 12, H is 1]

(a) CH₄

(b) CH

(d) CH₃

Solutions :

1.Ans: (a)

Manufacture – By hydrolysis of starch with hot dill. Mineral acids

2.Ans: (a)

Structure of DNA – It consists of two polynucleotide chains, each chain forms a right handed helical spiral with ten bases in one turn of the spiral. The two chains coil to double helix and run in opposite direction held and run in opposite direction held together by hydrogen bonding.

3.Ans: (b)
Enzymes being biocatalyst can increase the rate of reaction upto 10 million times. Even very small account can accelerate a reactions.

4.Ans: (c)

Basically digestion means hydrolysis

5.Ans: (b)

– D glucose and b- D glucose are the isomers which differ in the orientation (configuration) of H and OH group around C₁ atom.

6.Ans: (a)

When antigens enter in to the body cells and destroy them, then antibodies being proteins are synthesised in the body and combine with antigens and destroy these antigens by forming inactive complexes. Therefore antibodies protein destroy antigens.

7.Ans: (b)

8.Ans: (c)

the hydrolysis of sucrose by boiling with mineral acid or by enzyme invertase of sucrose produces a mixture of equal molecules of D(+) glucose and D(-) Fructose.

9.Ans: (d) 2,-4- Dinitroflurobenzene, also known as Sanger’s reagent, reacts with the H₂N – group of the peptide to from 2,4- dintrophenyl (DNP) derivative of the peptide. The DNP derivative of the peptide is hydrolysed to give DNP derivative of the single amino acid

10.Ans: (b)

11.Ans: (b)

Fe is responsible for oxidation of water to O₂.

12.Ans: (b) Petide bonds are present in enzyme

13.Ans: (a)We know that ini the lipid metabolism, when palmitic acid is oxidised, then two carbon fragments are removed sequentially to form acetyl coenzyme. It enters the citric acid cycle for production of 130 ATP.

14.
Ans: (c)

In DNA, the complementary bases are adenine and guanine ; thymine and cytosine. Each nucleotide in DNA is composed of a nitrogen containing base, either guanine (G), adenine (A), thymine (T), or cytosine (C) as well as a monosaccharide sugar called deoxyribose and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone. According to base pairing rules (A with T and C with G), hydrogen bonds bind the nitrogenous bases of the two separate polynucleotide strands to make double-stranded DNA.

15.Ans: (d)

We know ath glucose reacts with one molecule of phenyl hydrazine to give phenyl hydrazine. When warmed with excess of phenylhydrazine, the secondary alcoholic group adajecent to the aldehyde group is oxidised by another molecule of phenylhydrazine to a ketonic group.
With this ketonic group, the third molecule of phenylhydrazine condenses to glucosazone. Therefore the value of X is 3.

16.Ans: (c)Fructose is the sweetest sugar.

17.Ans: (c) C₆H₁₂O₆ + 6O₂ +2ATP -> 6CO₂ + 6H₂O +38ATP Molecules

Net total number of ATP molecules evolved = 36 molecules.

18.Ans: (d)

Progesterone (Gestogens) is a steroid hormone ,which controls the development and maintainance of pregnancy. Thryoxine and Adrenaline are Amine hormones.

19.Ans: (d)

Na⁺, Cl^– and HCO₃^– are the electrolytes present in plasma solute in blood. Na⁺ and Cl^– helps in maintenance of osmotic pressure and fluid balance.

20.Ans: (b)

There are 20 amino acid in man out of which 10 amino acids are essential amino acids. These essential amino acids are supplied to our bodies by food which we take because they cannot be synthesised in the body. These are

(1) Valine

(2) leucine

(3)Isoleucine

(4) Phenyl alanine

(5) Threonine

(6) Methionine

(7) Lysine

(8) Tryphtho phone

(9) Arginine

(10)Histidine.

21.Ans: (b)

Chlorophyll contain Mg.

22.Ans: (c)

Gluoseconatin aldehyde group. Hence it give positive felling solution test.

23.Ans: (a)

Due to resonance C –N bond in protein acquires double bond character and it is smaller than usual C – N bond.

24.Ans: (a)

Starch is also know as amylum which occurs in all green plants. A molecule of starch (C₆H₁₀O₅) is built of a large number of a – glucose ring joined through oxygen –atom.

25.Ans: (d)

The hydrogen bonds are formed between the base(shown by dotted lines). Because of size and geometrics of the bases, the only possible pairing in DNA and between G (Guanine) and C (Cytosine) through three H – bonds and between A (Adensoine) and T (Thymine) through two H – bonds.

26.Ans: (a)

We know that cellulose (C₆H₁₂O₆) is the chief constituent of cell walls of plants. It is the most abundant organic substance found in nature. It is a polymer of glucose with 3500 repeat units in a chain.

27.Ans: (b)

Enzymes are made up of protein with specific structure.

28.Ans: (b)

All proteins are not found in L- form but they may be present in form of D or L

29.Ans: (d)

It is a common pathway for both the aerobic & anaerobic respiration in which 1 glucose molecule is converted to 2 molecules of pyruvate.

30.Ans: (c)

Phospholipids are derivatives of glycerol in which two of the hydroxyl groups are esterified with fatty acid while the third is esterified with some derivative of phosphoric acid with some alcohol such as choline, ethanolamine, serine or inositol.

31.Ans: (b)

= = 1

Amount of A = T and that of G = C

32.Ans: (d) The bond formed between two amino acids by the elimination of a water molecule is called peptide linkage or bond. The peptide bond is simply another name for amide bond.The product formed by linking amino acid molecules through peptide linkages. – CO – NH – , is called peptide.

33.Ans: (a)The sequence of bases in mRNA are read in a srial order in groups of three at a time. Each triplet of nucleotides (having a specific sequence of bases) in known as carbon. Each condon specifies one amino acid. Fujrther since, there are four baess. Therefore , 4³ = 64 triplets or condons are possible.

34.Ans: (d)Insulin helps in converting glucose to glycogen

35.Ans: (b)Triglycerides are lipids,. Hence these are hydrolysed by lipases to glycerol and fatty acid

36.Ans: (c)Haemoglobin acts as an oxygen carrier in the blood since it reacts with oxygen to form unstable oxyhaemoglobin which easily breaks to give back haemoglobin and oxygen.

37.Ans: (b)The a– helix structure is formed when the chain of a– amino acids coils as a right handed screw (called a– helix) because of the formation of hydrogen bonds between made groups of the same peptide chain. Ie. NH group in one unit is linked to carbonyl oxygen of the third unit by hydrogen bonding. This hydrogen bonding between different units is responsible for holding helix in a position.

38.Ans: (c)

39.Ans: (b)Cell membranes( plasma membranes) constitutes bailyer of phospholipid with embedded proteins. In huymans, lipids accounts for upto 79 % of cell membrane.40.

Ans: (d)Testorterone and aderenaline are steroid harmone., Thyroxin is non steroidedharmone glucagon is peptide harmone.

41.Ans: (a)The organic compounds other than carbohydrates, proteins which maintain normal growth and nutrition in the human body (but not produced in human body) are called vitamins.

43.Ans: (c) Each nucleic acid consists of a pentose sugar a heterocyclic base, and phosphoric acid. The sugar present in DNA is 2 –deoxy -D(-) ribose and the sugar present in RNA is D (-) ribose. The chirality of DNA and RNA molecules are du to the presence of sugar components.

44.Ans: (a)Thyroxine is an amino hormone.
45.Ans: (b)In DNA the complimentary base are Adenine and thymine.Guanine and cytosine The genetic information for cell is contained in the sequence of bases A, T , G and C in DNA molecule
46.Ans: (b)The DNA sequence that codes for a specific protein is called a Gene and thus every protein in a cell has a corresponding gene.

47.Ans: (c) Thyroxin is the only hormone among the given choices that contains iodine Its struct is as follows:

48.Ans: (a) Sucrose does not have free – CHO or CO group. Hence it does not undergo mutarotation.

49.Ans: (a)Tollen’s reagent is used to identify an aldehyde group −CHO because tollen’s reagent oxidizes aldehyde.Fructose is a carbohydrate that does not contain the aldehyde group but fructose show keto-enol tautomerism and thus isomerizes to glucose due to which it gives positive Tollen’s reagent test and silver mirror.

50.Ans: (c)

51.Ans: (d)When the proteins are subjected to the action of heat, mineral acids or alkali, the water soluble form of globular protein changes to water insoluble fibrous protein. This is called denaturation of proteinis. During denaturation secondary and tertiary structure of protein destroyed but primary structures remains intact.
52.Ans: (bd)

Enzymes are most reactive at optimum temperature. The optimum temperature for enzyme activity les between 40⁰C to 60⁰ C

53.Ans: (b)Beri – beri

54.Ans: (b)The base pairs of the two strand of DNA are linked together through H- bonds.

55. (c)

56.(d) Cortisone – sterols

57. (c)In DNA, adenine (A) and thymine (T) are joined by two hydrogen bonds while guanine (G) and cytosine (C) are joined by three hydrogen bonds. No other combination of four bases is possible. Hence, the sequence of complementary strand is TACGAACT.

58.(c)Central dogma model contains following steps :DNA RNA Protein

59(c) the sugar component in RNA is ribose and the sugar component in DNA is 2′-deoxyribose

60 (b)Cytochromes are conjugated proteins consisting of an apoprotein and a prosthetic group (haeme). The haeme consists of a porphyrin with a central iron atom. The name haemoglobin is the concatenation of haeme and globin, reflecting the fact that each subunit of haemoglobin is a globular protein with an embedded heme (or haem) group; each heme group contains an iron atom, and this is responsible for the binding of oxygen. The most common types of haemoglobin contains four such subunits, each with one heme group.

61(a)All monosaccharides whether aldoses or ketoses are reducing sugars. Disaccharides such as sucrose in which the two monosaccharide units are linked through their reducing centres i.e., aldehydic or ketonic groups are non-reducing.

62 (a)Fats→Long saturated Fatty acidss chain.

63 (d)Adrenaline hormones in creases pulse rate and controls blood pressure. It releases glucose from liver glycogen and fatty acids from fats in emergency

64 (c)In the process denaturation, secondary and tertiary structures of protein get destroyed but the primary structure remains undisturbed. Since denaturation reactions are not strong enough to break the peptide bonds, the primary structure (sequence of amino acids) remains the same after a denaturation process.Heat, acid, and alkali denature DNA molecule and a double strand of DNA converts into a single strand.

65(b) In aqueous medium, fructose is enolised and converted into aldehyde in basic medium. Generally all aldehydes reduce Tollen’s reagent, thus fructose can also reduces Tollen’s reagent.

66 (c) Glycosidic bond

67 (b) The constituents of nucleic acids are nitrogenous bases, sugar and phosphoric acid. The sugar present in DNA is D(-)-2-deoxyribose and the sugar present in RNA is D(-)-ribose. Due to these D(-)-sugar components, DNA and RNA molecules are chiral molecules.

68 (d) pepsin and trypsin

69. (c)All amino acids are optically active except glycine. Glycine is inactive because saturated carbon atoms are unsubstituted that’s why glycine is optically inactive.

• Glycine is known as photogenic alpha-amino acid. This is optically inactive.

• Glycine is the simplest amino acid that has only three groups there is no fourth group so glycine is not chiral so not optically active.

• All twenty amino acids have four different groups around a central carbon atom except glycine.

70. (d) Ceil membranes are mainly composed of phospholipids.

71. (d) Haemoglobin acts as oxygen carrier in the blood because four Fe²⁺ ions of each haemoglobin can bind with four molecules of O₂ and form oxyhaemoglobin 4Hb+4O₂⟶Hb₄O₈

72(c) Glycolysis is the first stage in the oxidation of glucose. It is an anaerobic process and involves the degradation of glucose into two molecules of pyruvate with the generation of two molecules of ATP.

73 (d) proteins with specific structure

74 (d) Insulin is hormone secreted by the pancreas that lowers blood glucose level by promoting the uptake of glucose by cells and the conversion of glucose of glycogen by liver and skeletal muscle.

75 (a) peptide bond

76 (c) Denaturation makes the protein more active.

77 (b)Amylose and Amylopectin are polymers of – D-glucose, so -link is not possible. Amylose is linear with 1 → 4 -linkage whereas Amylopectin is branched and has both 1 → 4 and 1 → 6 -linkages.

78 (c)