Here are 50 Assertion and Reason questions based on Chapter 14: Biomolecules from the CBSE Class 12 Chemistry NCERT book.
1. Assertion: Proteins are made up of amino acids.
Reason: The sequence of amino acids in a protein determines its
structure and function.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Proteins are polymers of amino acids, and their
sequence determines their 3D structure, which dictates their biological
function.
2. Assertion: Enzymes are biological catalysts that speed up
chemical reactions.
Reason: Enzymes lower the activation energy of a reaction
without being consumed in the process.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Enzymes act as catalysts by providing an alternate
reaction pathway with lower activation energy, speeding up reactions without
being consumed.
3. Assertion: Carbohydrates are the primary source of energy
for living organisms.
Reason: Carbohydrates are rich in oxygen, which makes them
highly reactive and energy-rich.
Answer: (C) Assertion is true, but reason is false.
Explanation: While carbohydrates are the primary energy source,
their energy comes from their carbon-hydrogen bonds, not the oxygen content. The
oxygen content helps in oxidation reactions.
4. Assertion: All enzymes are proteins.
Reason: Enzymes have a specific 3D structure that allows them
to perform catalytic functions.
Answer: (C) Assertion is true, but reason is false.
Explanation: While most enzymes are proteins, some RNA
molecules (ribozymes) also have catalytic functions. The reason for their
catalytic activity is the specific 3D structure.
5. Assertion: The primary structure of proteins refers to their
three-dimensional shape.
Reason: The primary structure of a protein is determined by the
sequence of amino acids in its polypeptide chain.
Answer: (B) Assertion is true, reason is true, but reason is
not the correct explanation for assertion.
Explanation: The primary structure of a protein refers to the
linear sequence of amino acids, not the three-dimensional shape. The 3D shape is
determined by higher-level structures like secondary and tertiary structures.
6. Assertion: Nucleic acids are made of nucleotides.
Reason: Nucleotides are composed of a nitrogenous base, a
sugar, and a phosphate group.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Nucleotides, the building blocks of nucleic acids
like DNA and RNA, consist of a nitrogenous base, a sugar, and a phosphate group.
7. Assertion: Cellulose is a polysaccharide found in the cell
wall of plants.
Reason: Cellulose is made up of glucose monomers connected by
beta-glycosidic bonds, which are difficult to digest by humans.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Cellulose consists of glucose monomers linked by
beta-glycosidic bonds, making it indigestible to humans as they lack the enzyme
required to break this bond.
8. Assertion: In DNA, adenine pairs with thymine.
Reason: In RNA, adenine pairs with uracil.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: In DNA, adenine pairs with thymine through
hydrogen bonding, and in RNA, adenine pairs with uracil due to the difference in
their structures.
9. Assertion: Vitamins are organic compounds required in small
amounts for normal metabolism.
Reason: They function as cofactors in enzymatic reactions.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Vitamins, particularly B vitamins, function as
coenzymes or cofactors, assisting enzymes in catalyzing metabolic reactions.
10. Assertion: Proteins exhibit a high level of specificity in
their functions.
Reason: The shape and structure of proteins are determined by
their amino acid sequences.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The specificity of a protein’s function is
determined by its 3D structure, which is dictated by the sequence of amino
acids.
11. Assertion: Disaccharides are formed by the condensation of
two monosaccharides.
Reason: The condensation reaction involves the removal of a
water molecule.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Disaccharides are formed by the condensation of
two monosaccharides, where a water molecule is removed, forming a glycosidic
bond.
12. Assertion: Fatty acids are the building blocks of lipids.
Reason: Fatty acids are long-chain carboxylic acids with
hydrophobic tails and hydrophilic heads.
Answer: (C) Assertion is true, but reason is false.
Explanation: Fatty acids are building blocks of lipids, but
their structure is typically hydrophobic (not having hydrophilic heads). The
amphipathic nature of lipids comes from their arrangement in phospholipids.
13. Assertion: A phospholipid bilayer forms the fundamental
structure of cell membranes.
Reason: Phospholipids have hydrophilic heads and hydrophobic
tails, which arrange themselves in a bilayer to minimize energy.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The amphipathic nature of phospholipids allows
them to form bilayers, with hydrophilic heads facing outward and hydrophobic
tails facing inward.
14. Assertion: Hydrolysis of proteins results in the breakdown
of peptide bonds.
Reason: The hydrolysis process involves the addition of a water
molecule, which breaks the peptide bond.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Hydrolysis of proteins involves adding water
molecules to break the peptide bonds between amino acids.
15. Assertion: Insulin is a protein hormone.
Reason: Insulin is composed of two polypeptide chains connected
by disulfide bonds.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Insulin is indeed a protein hormone and consists
of two polypeptide chains, which are held together by disulfide bonds.
16. Assertion: Enzymes are highly specific in their action.
Reason: Enzymes bind to substrates at their active sites and
catalyze specific reactions.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Enzymes are highly specific because their active
sites are shaped to fit only particular substrates, ensuring specific catalysis.
17. Assertion: DNA is double-stranded, while RNA is
single-stranded.
Reason: DNA stores genetic information, whereas RNA helps in
protein synthesis.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: DNA stores genetic information in a double-helix
structure, while RNA is single-stranded and helps in the process of
transcription and translation.
18. Assertion: The secondary structure of proteins includes
alpha helices and beta-pleated sheets.
Reason: These structures are stabilized by hydrogen bonds
between the peptide backbone.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The secondary structure of proteins involves alpha
helices and beta-pleated sheets, which are stabilized by hydrogen bonds in the
polypeptide backbone.
19. Assertion: The tertiary structure of a protein refers to
its overall 3D shape.
Reason: The tertiary structure is stabilized by interactions
such as hydrogen bonds, hydrophobic interactions, and disulfide bonds.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The tertiary structure of proteins is the final 3D
conformation, stabilized by a variety of interactions, including hydrogen bonds,
hydrophobic interactions, and disulfide bridges.
20. Assertion: Proteins can denature when exposed to extreme
conditions like high temperature or extreme pH.
Reason: Denaturation involves the disruption of non-covalent
interactions, causing the protein to lose its native structure.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Denaturation occurs when high temperatures or
extreme pH break non-covalent bonds, causing proteins to lose their functional
3D structure.
21. Assertion: Lipids are insoluble in water.
Reason: Lipids have non-polar hydrocarbon chains that do not
interact well with water molecules.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Lipids are non-polar and hydrophobic, so they are
insoluble in water, which is polar.
22. Assertion: Vitamin A is important for vision.
Reason: Vitamin A is a precursor of retinal, which is involved
in light detection in the retina.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Vitamin A is crucial for the formation of retinal,
a component of the photoreceptor pigments in the retina that help in vision.
23. Assertion: Glucose is a monosaccharide.
Reason: Glucose is a hexose sugar with six carbon atoms and can
form both alpha and beta forms in aqueous solution.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Glucose is a six-carbon monosaccharide that forms
two isomers (alpha and beta) due to the anomeric carbon in its cyclic form.
24. Assertion: RNA is involved in the synthesis of proteins in
cells.
Reason: RNA carries the genetic information from DNA to the
ribosomes, where proteins are synthesized.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: RNA carries the genetic information from DNA in
the form of messenger RNA (mRNA), which is then used in the synthesis of
proteins.
25. Assertion: Insulin is a peptide hormone.
Reason: Insulin consists of amino acid chains and functions to
regulate blood glucose levels.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Insulin is composed of two peptide chains and
plays a crucial role in regulating blood glucose levels.
26. Assertion: Glycogen is a storage form of glucose in
animals.
Reason: Glycogen is composed of glucose monomers linked by
alpha-glycosidic bonds.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Glycogen is a polysaccharide made of glucose units
linked by alpha-glycosidic bonds, which serves as the main energy reserve in
animals.
27. Assertion: Cholesterol is a type of lipid.
Reason: Cholesterol is important for the fluidity of cell
membranes and serves as a precursor to steroid hormones.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Cholesterol is a lipid that maintains membrane
fluidity and is a precursor for steroid hormones like testosterone and estrogen.
28. Assertion: Hydrolysis reactions involve the breaking of
bonds through the addition of water.
Reason: In hydrolysis, water molecules split into hydroxide and
hydrogen ions to break bonds in biomolecules.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Hydrolysis involves adding water to break covalent
bonds, which is crucial in breaking down complex molecules into simpler
components.
29. Assertion: RNA plays a role in protein synthesis.
Reason: RNA transfers the genetic code from DNA to ribosomes
for protein assembly.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: RNA carries the genetic code from DNA to ribosomes
for protein synthesis, playing a central role in transcription and translation.
30. Assertion: The structural formula of glucose shows six
carbon atoms.
Reason: Glucose is classified as a hexose sugar because it
contains six carbon atoms.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Glucose is a six-carbon monosaccharide, thus
classified as a hexose sugar.
31. Assertion: Peptide bonds are formed between amino acids
during protein synthesis.
Reason: Peptide bonds are covalent bonds that form between the
carboxyl group of one amino acid and the amino group of another.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Peptide bonds form between amino acids during
protein synthesis, linking the amino group of one amino acid with the carboxyl
group of another.
32. Assertion: DNA is a double-stranded molecule.
Reason: DNA strands are held together by hydrogen bonds between
complementary nitrogenous bases.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: DNA has two strands, and the strands are held
together by hydrogen bonds between complementary nitrogenous bases
(adenine-thymine, guanine-cytosine).
33. Assertion: Hydrocarbons are non-polar compounds.
Reason: Hydrocarbons consist of carbon and hydrogen atoms, both
of which are similar in electronegativity.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Hydrocarbons are non-polar because carbon and
hydrogen have similar electronegativities, resulting in no dipoles in their
bonds.
34. Assertion: Fats and oils are types of lipids.
Reason: Both fats and oils are composed of glycerol and fatty
acids.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Fats and oils are lipids formed by the
esterification of glycerol with fatty acids.
35. Assertion: Denaturation of proteins results in the loss of
their biological activity.
Reason: Denaturation disrupts the protein’s 3D structure,
affecting its ability to bind to substrates.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Denaturation involves changes in the protein's 3D
structure, which can lead to loss of biological activity due to disruption of
active sites.
36. Assertion: Peptide bonds are broken during the digestion of
proteins.
Reason: Peptide bonds are broken by proteolytic enzymes like
pepsin during digestion.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Proteolytic enzymes such as pepsin break down
peptide bonds during digestion, converting proteins into smaller peptides.
37. Assertion: Proteins function as enzymes, antibodies, and
hormones.
Reason: The specific function of a protein is determined by its
sequence of amino acids and 3D structure.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The function of a protein is determined by its
unique amino acid sequence and 3D shape, enabling it to act as an enzyme,
antibody, or hormone.
38. Assertion: Glycogen is stored in the liver and muscles in
animals.
Reason: Glycogen is the storage form of glucose in animals,
providing an energy reserve.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Glycogen, stored in the liver and muscles, is a
polysaccharide that serves as a form of glucose storage, providing energy during
fasting or exercise.
39. Assertion: The human body cannot synthesize essential amino
acids.
Reason: Essential amino acids must be obtained through the
diet, as the body lacks the enzymes to synthesize them.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Essential amino acids cannot be synthesized by the
body and must be supplied through the diet, as the body lacks the necessary
enzymes for their synthesis.
40. Assertion: Catalysts increase the rate of reaction by
lowering the activation energy.
Reason: Enzymes are biological catalysts that speed up
biochemical reactions in living organisms.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Catalysts, including enzymes, lower the activation
energy, thereby increasing the rate of chemical reactions without being consumed
in the process.
41. Assertion: The secondary structure of a protein includes
alpha-helices and beta-pleated sheets.
Reason: The secondary structure is stabilized by hydrogen bonds
between the backbone atoms of the polypeptide chain.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The secondary structure of proteins includes
structures like alpha-helices and beta-pleated sheets, which are stabilized by
hydrogen bonds between the carbonyl oxygen of one amino acid and the amino
hydrogen of another.
42. Assertion: Nucleic acids are responsible for storing and
transmitting genetic information.
Reason: DNA stores genetic information, and RNA helps in
protein synthesis.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: DNA is the molecule that stores genetic
information, and RNA plays a key role in transmitting this information for
protein synthesis.
43. Assertion: The structure of water is crucial for its
solvent properties.
Reason: Water molecules are polar, with a partially positive
charge on the hydrogen atoms and a partially negative charge on the oxygen atom.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Water's polarity allows it to dissolve many ionic
and polar substances, making it an excellent solvent.
44. Assertion: Enzymes are highly specific in their activity.
Reason: Enzymes have an active site that is specific to a
particular substrate.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Enzymes are specific due to their active site
shape, which is complementary to the substrate's shape, ensuring only specific
reactions are catalyzed.
45. Assertion: Vitamin D is synthesized in the skin when
exposed to sunlight.
Reason: Ultraviolet light converts a cholesterol derivative in
the skin into vitamin D.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Ultraviolet (UV) light from the sun triggers a
chemical reaction that converts a cholesterol derivative in the skin to vitamin
D, which is essential for calcium absorption.
46. Assertion: Proteins can function as enzymes, structural
components, and antibodies.
Reason: The diverse roles of proteins are determined by their
unique amino acid sequences and three-dimensional structures.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Proteins can serve many functions due to the
variety of their structures, each suited to specific roles such as catalysis
(enzymes), support (structural proteins), or immunity (antibodies).
47. Assertion: Carbohydrates are important energy sources for
living organisms.
Reason: Carbohydrates are easily broken down to release energy
in the form of ATP.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Carbohydrates, such as glucose, are rapidly
metabolized to produce ATP, the primary energy currency of the cell.
48. Assertion: The energy stored in ATP is used for cellular
processes.
Reason: ATP contains high-energy phosphate bonds that, when
broken, release energy.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: ATP contains high-energy bonds between its
phosphate groups, and when these bonds are broken, energy is released for use in
various cellular functions.
49. Assertion: The pH of a solution affects enzyme activity.
Reason: Enzymes have an optimal pH at which they function best,
and deviations from this pH can reduce their activity.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Enzymes are pH-sensitive, and their structure and
function can be altered by changes in pH, which affects the rate of biochemical
reactions.
50. Assertion: Osmosis is the movement of water across a
selectively permeable membrane.
Reason: Osmosis occurs from a region of lower solute
concentration to a region of higher solute concentration.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Osmosis refers to the movement of water through a
semi-permeable membrane, driven by the concentration gradient of solutes.
51. Assertion: DNA replication is semi-conservative.
Reason: Each new DNA molecule consists of one strand from the
original molecule and one newly synthesized strand.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: During DNA replication, each strand of the
original DNA serves as a template for the synthesis of a new complementary
strand, resulting in two DNA molecules, each with one original and one new
strand.
52. Assertion: The nucleolus is the site of ribosome synthesis.
Reason: Ribosomal RNA (rRNA) is synthesized in the nucleolus
and combined with proteins to form ribosome subunits.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The nucleolus is responsible for producing rRNA,
which then combines with proteins to form the subunits of ribosomes, essential
for protein synthesis.
53. Assertion: Active transport requires energy.
Reason: Active transport moves molecules against their
concentration gradient, which requires energy in the form of ATP.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Active transport moves substances from an area of
lower concentration to an area of higher concentration, which requires energy to
pump molecules across the membrane.
54. Assertion: Chloroplasts are involved in photosynthesis.
Reason: Chloroplasts contain chlorophyll, which absorbs light
energy for the synthesis of glucose.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Chloroplasts contain chlorophyll, a pigment that
captures light energy and converts it into chemical energy during photosynthesis
to produce glucose.
55. Assertion: The process of transcription involves copying a
gene’s DNA sequence into RNA.
Reason: In transcription, RNA polymerase reads the DNA template
and synthesizes a complementary RNA molecule.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Transcription is the process by which RNA is
synthesized from a DNA template by RNA polymerase, transferring the genetic code
into an RNA format.
56. Assertion: Lipids are stored in adipose tissue.
Reason: Lipids are hydrophobic and stored in adipocytes for
energy reserve and insulation.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Adipose tissue stores lipids in the form of
triglycerides, which provide long-term energy reserves and help insulate the
body.
57. Assertion: The mitochondria are known as the powerhouses of
the cell.
Reason: Mitochondria generate ATP, which is the main energy
source for cellular activities.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Mitochondria are responsible for producing ATP
through cellular respiration, providing energy for various cellular functions.
58. Assertion: Proteins are made up of amino acids.
Reason: Amino acids are the building blocks of proteins, and
their sequence determines the protein’s structure and function.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Proteins are polymers made up of amino acid
monomers, and the sequence of amino acids determines the protein’s structure,
which in turn dictates its function.