Class 12Chemistry | Biomolecules| MCQs
Class 12Chemistry | Biomolecules| MCQs
Question 1:
Which one of the following reactions is not explained by the open
chainStructureof glucose?
(a) Formation of pentaacetate of glucose with acetic anhydride.
(b) formation of addition product with 2,4 DNP reagent
(c) Silver mirror formation with Tollen’s reagent
(d) existence of alpha and beta forms of glucose.
Answer: (d) existence of alpha and beta forms of glucose.
Existence of alpha and beta forms of glucose explained by the open chain
Structure of glucose.
Question 2:
Which of the following statement is correct?
(a) Fibrous proteins are generally soluble in water
(b) Albumin is an example of fibrous proteins
(c) In fibrous proteins, the structure is stabilised by hydrogen bonds and
disulphide bonds
(d) pH does not affect the primary structure of protein.
Answer: (d) pH does not affect the primary structure of protein.
pH does not affect the primary structure of protein but it affects the tertiary
structure.
Question 3:
Which of the following is a polysaccharide?
Class 12Chemistry | Biomolecules| MCQs
(a) glucose
(b) maltose
(c) glycogen
(d) lactose
Answer: (c) glycogen
Glycogen is a polymer of glucose.
Question 4:
In which of the following cases blood cells will shrink:
(a) when placed in water containing more than 0.9% (mass/ volume) NaCl
solution.
(b) when placed in water containing less than 0.9% (mass /volume) NaCl
solution.
(c) when placed in water containing 0.9% (mass/volume) NaCl solution.
(d) when placed in distilled water.
Answer: (a) when placed in water containing more than 0.9% (mass/ volume)
NaCl solution.
When placed in water containing more than 0.9% (mass/ volume) NaCl
solution because fluid inside blood cells is isotonic with 0.9% NaCl solution.
Question 5:
Which of the following polymer is stored in the liver of animals?
(a) Amylose
(b) Cellulose
(c) Amylopectin
Class 12Chemistry | Biomolecules| MCQs
(d) Glycogen
Answer: (d) Glycogen
The carbohydrates are stored in animal body as glycogen. It is also known as
animal starch because its structure is similar to amylopectin and is rather more
highly branched. It is present in liver, muscles and brain.
Question 6:
Proteins are found to have two different types of secondary structures viz. α-
helix and β-pleated sheet structure. α-helix structure of protein is stabilised by:
(a) Peptide bonds
(b) van der Waals forces
(c) Hydrogen bonds
(d) Dipole-dipole interactions
Answer: (c) Hydrogen bonds
α-helix and β-pleated sheet structure: These structures arise due to the regular
folding of the backbone of the polypeptide chain due to hydrogen bonding
between >C—O and —NH— group of the peptide bond.
α-Helix is one of the most common ways in which a polypeptide chain forms all
possible hydrogen bond by twisting into a right-handed screw (helix) with the -
NH group of each amino acid residue hydrogen bonded to the >C=O of an
adjacent turn of the helix.
Question 7:
Class 12Chemistry | Biomolecules| MCQs
In disaccharides, if the reducing groups of monosaccharides i.e., aldehydic or
ketonic groups are bonded, these are non-reducing sugars. Which of the
following disaccharide is a non-reducing sugar?
Answer:
One of the common disaccharides is sucrose which on hydrolysis gives
equimolar mixture of D- (+)-glucose and D- (-) fructose. These two
monosaccharides are held together by a glycosidic linkage between C 1 of α-
Class 12Chemistry | Biomolecules| MCQs
glucose and C2 of beta-fructose. Since the reducing groups of glucose and
fructose are involved in glycosidic bond formation, sucrose is a non-reducing
sugar.
Question 8:
Nucleic acids are the polymers of
(a) Nucleosides
(b) Nucleotides
(c) Bases
(d) Sugars
Answer: (b) Nucleotides
Nucleic acids are long chain polymers of nucleotides, so they are also called
polynucleotides.
Question 9:
DNA and RNA contain four bases each. Which of the following bases is not
present in RNA?
(a) Adenine
(b) Uracil
(c) Thymine
(d) Cytosine
Answer: (c) Thymine
DNA contains four bases viz. adenine (A), guanine (G), cytosine (C) and thymine
(T). RNA also contains four bases; the first three bases are same as in DNA but
the fourth one is uracil (U).
Class 12Chemistry | Biomolecules| MCQs
Question 10:
Three cyclic structures of monosaccharides are given below which of these are
anomers.
(a) I and II
(b) II and III
(c) I and III
(d) III is anomer of I and II
Answer: (a) I and II
This behaviour could not be explained by the open chain structure (I) for
glucose. It was proposed that one of the —OH groups may add to the —CHO
group and form a cyclic hemiacetal structure. It was found that glucose forms a
six-membered ring in which —OH at C-5 is involved in ring formation. This
explains the absence of —CHO group and also existence of glucose in two
forms as shown below.
Class 12Chemistry | Biomolecules| MCQs
Question 11:
Structure of a disaccharide formed by glucose and fructose is given below.
Identify anomeric carbon atoms in monosaccharide units.
(a ‘a’ carbon of glucose and ‘a’ carbon of fructose.
(b) ‘a’ carbon of glucose and ‘e’ carbon of fructose.
(c) ‘a’ carbon of glucose and ‘b’ carbon of fructose.
(d) ‘f’ carbon of glucose and ‘f’ carbon of fructose.
Answer: (c) ‘a’ carbon of glucose and ‘b’ carbon of fructose.
Two monosaccharides are held together by a glycosidic linkage between C 1 of
α-glucose and C2 of β-fructose.
Class 12Chemistry | Biomolecules| MCQs
Question 12:
Which one of the following statements is correct about sucrose?
(a) It can reduce Tollen’s reagent however cannot reduce Fehling’s reagent
(b) It undergoes mutarotation like glucose and fructose
(c) It undergoes inversion in the configuration on hydrolysis
(d) It is laevorotatory in nature.
Answer: (c) It undergoes inversion in the configuration on hydrolysis
Sucrose undergoes inversion in the configuration on hydrolysis.
Question 13:
A D-carbohydrate is:
(a) Always dextrorotatory
(b) Always laevorotatory
(c) Always the minor of the corresponding L-carbohydrate
(d) None of these
Answer: (d) None of these
Option (d) None of these. In these three no one is the D- carbohydrate.
Option (a) Always dextrorotatory
A D-carbohydrates is not always dextrorotatory.
So, it is incorrect.
Option (b) is incorrect
Option (b) Always laevorotatory
A D- carbohydrates is not always laevorotatory.
So, it is incorrect.
Option (c) is incorrect
Class 12Chemistry | Biomolecules| MCQs
(c) Always the mirror of the corresponding L- carbohydrate
A D- carbohydrates is not always the mirror of the corresponding L-
Carbohydrate.
So, this option is incorrect.
Question 14:
When the number of amino acids is more than 10, then the product called
_____.
Answer: When the number of amino acids is more than 10, then the product
called polypeptide.
When more than ten amino acids react with each other the product formed is
called Polypeptide.
Assertion Reason Based Questions
In the following questions from 15 to 18 a statement of assertion followed by
a statement of reason is given. Choose the correct answer out of the
following choices.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Class 12Chemistry | Biomolecules| MCQs
Question 15:
Assertion (A): Desmolysing enzymes are those which catalyse the reactions by
hydrolysis.
Reason (R): Digestive enzymes are hydrolysing in nature.
Answer: (d) A is false but R is true.
Desmolysing enzymes are those which catalyse reactions by the other methods
other than hydrolysis, e.g., aldolases, dehydrogenases, oxidases, etc. Digestive
enzymes function by catalysing hydrolysis. Larger molecules are broken into
smaller ones. They are grouped into three types - proteolytic (breaks protein
molecule), amylolytic (breaks sugar molecule) and lipolytic (breaks lipid
molecule).
Question 16:
Assertion (A): Enzymes are defined as biological proteins.
Reason (R): Chemically all enzymes are globular proteins.
Answer: (a) Both A and R are true and R is the correct explanation of A
All biological reactions are catalysed by special catalysis called enzyme; thus,
enzymes are defined as biological proteins. Also, enzymes are small organic
molecules which are weakly held to the protein and can be easily separated by
dialysis. Therefore, chemically all enzymes are globular proteins.
Question 17:
Assertion (A): DNA molecules and RNA molecules are found in the nucleus of
cell.
Reason (R): On heating, enzymes do not lose their specific activity.
Class 12Chemistry | Biomolecules| MCQs
Answer: (d) A is false but R is true.
DNA molecules are found primarily in the nucleus of the cell but RNA
molecules are found outside the nucleus. By heating, its special structural
arrangement is changed irreversibly, this result in the conversion of enzyme
into a fibrous or insoluble form. Due to this irreversible change, enzymes lose
their specific activity when heated.
Question 18:
Assertion (A): The two strands of DNA are complementary to each other
Reason (R): The hydrogen bonds are formed between specific pairs of bases.
Answer: (a) Both A and R are true and R is the correct explanation of A
Two DNA strands are complementary to each other. Adenine forms hydrogen
bond with thymine and guanine base pairs with cytosine. They follow base
complementary rule.
Question 19:
Invert sugar is:
(a) A type of cane sugar
(b) Optically inactive form of sugar
(c) Mixture of glucose and galactose
(d) Mixture of glucose and fructose in equimolar quantities.
Answer: (d) Mixture of glucose and fructose in equimolar quantities.
Class 12Chemistry | Biomolecules| MCQs
Sucrose which is an equimolar mixture of glucose and fructose on hydrolysis
brings about a change in the sign of rotation from dextro (+) to laevo (-) and
the product is named as invert sugar.
Hence, invert sugar is a mixture of glucose and fructose in equimolar
quantities.
Question 20:
The sequence in which amino acids are linked to one another in a protein
molecule is called its:
(a) Primary structure
(b) Secondary structure
(c) Tertiary structure
(d) Quaternary structure
Answer: (a) 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 said to be the primary structure of that
protein.
Question 21:
Observation of 'Ruhemann's purple' is a confirmatory test for the presence of:
(a) Starch
(b) Reducing sugar
(c) Protein
(d) Cupric ion
Class 12Chemistry | Biomolecules| MCQs
Answer: (c) Protein
Ninhydrin (2,2-dihydroxyindane-1,3-dione) is a chemical used to detect alpha
amino acids and also free amino acids and carboxylic acid groups on proteins
and peptides. When about 0.5 mL of a 0.1% solution of ninhydrin is boiled with
few mL of amino acid or protein solution a blue colour develops. Ninhydrin
degrades amino acids into aldehydes, ammonia and CO2 through a series of
reactions, the net result is ninhydrin in a partially form of hydrindatin.
Ninhydrin then condenses with ammonia and hydrindatin to produce an
intensely blue or purple pigment, sometimes called 'Ruhemann's purple'.
Class 12Chemistry | Biomolecules| MCQs
Question 22:
Which of the following B group vitamins can be stored in our body?
(a) Vitamin B1
(b) Vitamin B2
(c) Vitamin B6
(d) Vitamin B12
Answer: (d) Vitamin B12
Water soluble vitamins must be supplied regularly in diet because they are
readily excreted in urine and cannot be stored (except vitamin B12) in our body.
Question 23:
Which of the following statements regarding DNA fingerprinting is incorrect?
(a) It is used in forensic laboratories for identification of criminals.
Class 12Chemistry | Biomolecules| MCQs
(b) It cannot be altered by surgery.
(c) It is different for every cell and cannot be altered by any known treatment.
(d) It is used to determine paternity of an individual.
Answer: (c) DNA fingerprinting cannot be used for paternity testing
DNA fingerprinting is same for every cell and cannot be altered by any known
treatment.
Case-Study Based Questions
Question 24:
Read the passage given below and answer the following questions:
Adenosine triphosphate (ATP) is the energy-carrying molecule found in the
cells of all livingthings. ATP captures chemical energy obtained from the
breakdown of food molecules andreleases it to fuel other cellular processes.
ATP is a nucleotide that consists of three mainstructures: the nitrogenous
base, adenine; the sugar, ribose; and a chain ofthree phosphate groups bound
to ribose. The phosphate tail of ATP is the actual power sourcewhich the cell
taps. Available energy is contained in the bonds between the phosphates and
isreleased when they are broken, which occurs through the addition of a water
molecule (aprocess called hydrolysis). Usually only the outer phosphate is
removed from ATP to yieldenergy; when this occurs ATP is converted to
adenosine diphosphate (ADP), the form ofthe nucleotide having only two
phosphates.The importance of ATP (adenosine triphosphate) as the main
source of chemical energy inliving matter and its involvement in cellular
processes has long been recognized. The primarymechanism whereby higher
Class 12Chemistry | Biomolecules| MCQs
organisms, including humans, generate ATP is throughmitochondrial oxidative
phosphorylation. For the majority of organs, the main metabolic fuel
is glucose, which in the presence of oxygen undergoes complete combustion to
CO2 and H2O:
C6H12O6 + 6O2 6O2 + 6H2O + energy
The free energy (ΔG) liberated in this exergonic (ΔG is negative) reaction is
partially trappedas ATP in two consecutive processes: glycolysis (cytosol) and
oxidative phosphorylation(mitochondria). The first produces 2 mol of ATP per
mol of glucose, and the second 36 molof ATP per mol of glucose. Thus,
oxidative phosphorylation yields 17-18 times as muchuseful energy in the form
of ATP as can be obtained from the same amount of glucose by
glycolysis alone.
The efficiency of glucose metabolism is the ratio of amount of energy
produced when 1 molof glucose oxidised in cell to the enthalpy of combustion
of glucose. The energy lost in theprocess is in the form of heat. This heat is
responsible for keeping us warm.
1. Cellular oxidation of glucose is a:
(a) spontaneous and endothermic process
(b) non spontaneous and exothermic process
(c) non spontaneous and endothermic process
(d) spontaneous and exothermic process
2. What is the efficiency of glucose metabolism if 1 mole of glucose gives
38ATPenergy? (Given: The enthalpy of combustion of glucose is 686 kcal,
1ATP= 7.3kcal)
(a) 100%
Class 12Chemistry | Biomolecules| MCQs
(b) 38%
(c) 62%
(d) 80%
3.Which of the following statement is true?
(a) ATP is a nucleoside made up of nitrogenous base adenine and ribose sugar.
(b) ATP consists the nitrogenous base, adenine and the sugar, deoxyribose.
(c) ATP is a nucleotide which contains a chain of three phosphate groups
bound toribose sugar.
(d) The nitrogenous base of ATP is the actual power source.
4. Nearly 95% of the energy released during cellular respiration is due to:
(a) glycolysis occurring in cytosol
(b) oxidative phosphorylation occurring in cytosol
(c) glycolysis in occurring mitochondria
(d) oxidative phosphorylation occurring in mitochondria
5. Which of the following statements is correct?
(a) ATP is a nucleotide which has three phosphate groups while ADP is a
nucleosidewhich three phosphate groups.
(b) ADP contains a nitrogenous bases adenine, ribose sugar and two phosphate
groupsbound to ribose.
(c) ADP is the main source of chemical energy in living matter.
(d) ATP and ADP are nucleosides which differ in number of phosphate groups.
Answer.
1. (d) spontaneous and exothermic process
Class 12Chemistry | Biomolecules| MCQs
Cellular oxidation of glucose is a spontaneous and exothermic process.
2. (b) 38%
Glucose catabolism yields a total of 38ATP. 38 ATP x 7.3 kcal/mol ATP=262
kcal. Glucose has 686 kcal. Thus, the efficiency of glucose metabolism is
(262/686) x100=38%.
3. (c)
ATP is a nucleotide which contains a chain of three phosphate groups bound to
ribose sugar.
4. (d)
oxidative phosphorylation occurring in mitochondria
5. (b)
ADP contains a nitrogenous bases adenine, ribose sugar and two phosphate
groups bound to ribose.
Question 25:
The basic chemical formula of DNA is now well established. As shown in Figure
1 it consistsof a very long chain, the backbone of which is made up of alternate
sugar and phosphategroups, joined together in regular 3' 5' phosphate di-ester
linkages. To each sugar is attacheda nitrogenous base, only four different kinds
of which are commonly found in DNA. Two ofthese---adenine and guanine---
are purines, and the other two thymine and cytosine-arepyrimidines. A fifth
base, 5-methyl cytosine, occurs in smaller amounts in certain organisms,and a
sixth, 5-hydroxy-methyl-cytosine, is found instead of cytosine in the T even
Class 12Chemistry | Biomolecules| MCQs
phages. Itshould be noted that the chain is unbranched, a consequence of the
regular internucleotidelinkage. On the other hand, the sequence of the
different nucleotides is, as far as can beascertained, completely irregular. Thus,
DNA has some features which are regular, and somewhich are irregular. A
similar conception of the DNA molecule as a long thin fibre isobtained from
physicochemical analysis involving sedimentation, diffusion, light
scattering,and viscosity measurements. These techniques indicate that DNA is
a very asymmetricalstructure approximately 20 A wide and many thousands of
angstroms long. Estimates of itsmolecular weight currently center between 5 X
106 and 107(approximately 3 x104nucleotides). Surprisingly each of these
measurements tend to suggest that the DNA isrelatively rigid, a puzzling
finding in view of the large number of single bonds (5 pernucleotide) in the
phosphate-sugar back bone. Recently these indirect inferences have
beenconfirmed by electron microscopy
1. Purines present in DNA are:
(a) adenine and thymine
(b) guanine and thymine
(c) cytosine and thymine
(d) adenine and guanine
2. DNA molecule has ___________ internucleotide linkage and __________
sequence of thedifferent nucleotides.
(a) regular, regular
(b) regular, irregular
(c) irregular, regular
(d) irregular, irregular
Class 12Chemistry | Biomolecules| MCQs
3. DNA has a ___________ backbone
(a) phosphate -purine
(b) pyrimidines- sugar
(c) phosphate- sugar
(d) purine- pyrimidine
4. Out of the four different kinds of nitrogenous bases which are commonly
found in DNA,___________ has been replaced in some organisms.
(a) adenine
(b) guanine
(c) cytosine
(d) thymine
Answer:
1. (d) adenine and guanine
Purines present in DNA are adenine and guanine
2. (b) regular, irregular
DNA molecule has regular internucleotide linkage and irregular sequence of
thedifferent nucleotides.
3. (c) phosphate- sugar
DNA has a phosphate- sugar backbone.
4. (d) thymine
Class 12Chemistry | Biomolecules| MCQs
Out of the four different kinds of nitrogenous bases which are commonly
found in DNA, thymine has been replaced in some organisms.
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