BIOMELECULES

CARBOHYDRATES Definition
Definitions Chemically, the
 Carbohydrates (hydrates of carbon) are naturally, Carbohydrates may be defined as
occurring compounds having general formula Cx(H2O)y , optically active polyhydroxy
which are constantly produced in nature & participate in aldehydes or ketones or the
many important bio-chemical reactions compounds which produce such
 But some compounds which have formula according units on hydrolysis.
to Cx (H2O)y are not known as carbohydrate
Eg: Formaldehyde Acetic acid Lactic acid
 There are many compounds, which shows chemical behaviour of carbohydrate but do not confirm the
general formula Cx (H2O)y such as C5H10O4 (2-deoxyribose) C6H12O5 (Rahmnose)
 Carbohydrates, the energy source of living beings, are the most abundant organic compound around
us.
 metabolic process in the living beings, glucose is usually oxidized into carbon dioxide and water to
provide energy to the cell for their functioning.
Classification of Carbohydrates
Monosaccharides Oligosaccharides Polysaccharides
Simplest carbohydrates Cannot be Carbohydrates which give 2 to 10 Carbohydrates which on
hydrolysed into simpler monosaccharide units on hydrolysis give large number of
compounds hydrolysis monosaccharide units.
E.g., Glucose, mannose E.g, Sucrose, Lactose, Maltose E.g. Cellulose, starch
Monosaccharides (simple sugars)
 These are the sugars which cannot be hydrolysed into smaller molecules. General formula is CnH2nOn
 About twenty monosaccharides are known to exist in nature. Some examples are fructose, glucose,
ribose, etc.
 If CHO group is present in monosaccharide, then it is known as aldose.
 If keto group is present in monosaccharide, then it is known as ketose.
Oligosaccharides
 These are the sugars which yields 2-10 monosaccharides units on hydrolysis.
 Disaccharides : Two monosaccharide unit on hydrolysis (may or may not be same). Ex. Sucrose,
Maltose
 Trisaccharides : Three monosaccharide unit on hydrolysis.
Polysaccharides
 These are the non-sugars which yield a large no of monosaccharide units on hydrolysis.
 Polysaccharides are not sweet in taste, hence they are also called non-sugars.
 General formula – (C6H10O5 )n . Ex. Starch, Cellulose, Glycogen etc. Answer me !!!
Reducing and Non-Reducing Sugars
 Those sugars or carbohydrates which reduce Fehling’s solution and Fructose contains a keto
Tollens reagent are referred to as reducing sugars. group but still it reduces
 All monosaccharides whether aldose or ketose are reducing sugars. Tollens’ reagent. Why?
BODHI NOTES

 In disaccharides, when the reducing groups of monosaccharides, that is, aldehydic or ketonic groups,
are bonded, then these are referred to as non reducing sugars. e.g., sucrose.
Glucose
 Glucose occurs in both free and combined forms in nature.
 It is present in honey and sweet fruits.
 Also, glucose is present in large amounts in ripe grapes, so it is known as grapes sugar.
 Glucose is the unit of starch, cellulose and glycogens.
 BIOMELECULES
Preparation of Glucose
(1) From Sucrose (Cane sugar)
Fructose and glucose are obtained in equal amounts when sucrose is boiled with dil. HCl or H2SO4 in
alcoholic solution.

(2) From Starch

Glucose is obtained commercially by the hydrolysis of starch by boiling it at 393 K with dil. H2SO4.

Structure of Glucose
Glucose is aldohexose and is also called dextrose. C6H12O6 is its molecular formula.

Reactions of Glucose
Oxidation

 Dicarboxylic acid, saccharic acid can be yielded by oxidizing both glucose as well as gluconic acid
with nitric acid.
 This indicates the presence of a primary alcoholic (–OH) group in glucose.
NOTES

BODHI

BODHI NOTES
BIOMELECULES

(2) Reduction
 On prolonged heating with HI, there is formation of n-hexane (Straight Chain).

(3) Cyanohydrin Fomation

 It gives cyanohydrin when added a molecule of hydrogen cyanide.

(4) Oxime Formation

 To form an oxime glucose is reacts with hydroxylamine.

(5) Reaction with phenylhydrazine (formation of osazone)

(6) Acetylation
 Glucose pentaacetate is formed by Acetylation of glucose with acetic anhydride; this also confirms the
presence of five –OH groups.
 Five –OH groups should be attached to different carbon atoms.
BODHI NOTES
 BIOMOLECULES
Structure of glucose was proposed as

Cyclic Structure of Glucose

 The structure of glucose explained most of its properties but the following reactions and facts could
not be explained by this structure.
 The pentaacetate of glucose does not react with hydroxylamine it is indicated by the absence of free
—CHO group indicates.
 Two different crystalline forms of glucose. Named as

NOTES

BODHI
a) α-D(+) Glucose The a-form of glucose (m.p. 419 K) is obtained by crystallisation from
concentrated solution of glucose at 303 K.
b) β-D(+) Glucose The b-form (m.p. 423 K) is obtained by crystallisation from hot and saturated
aqueous solution at 371 K.

Howarth Structure
 Pyranose structure is a six-membered cyclic structure of glucose (a– or b–), in analogy with pyran.
 Pyran is a cyclic organic compound with five carbon atoms and one oxygen atom in the ring.
 The Haworth structures given below are the cyclic structure of glucose.

FRUCTOSE
 Fructose is an important ketohexose. It also has the molecular formula C6 H12 O6 .
 It is obtained by the hydrolysis of disaccharide. Ex : Hydrolysis of Sucrose Glucose & Fructose
 It is a natural monosaccharide found in vegetables, fruits and honey.
BODHI NOTES

Cyclic Structure of Fructose

BIOMOLECULES

This structure is obtained by the addition of —OH at C5 to the ketonic group, which produce two cyclic
forms.

Howarth Structure
The ring has an analogy to the compound furan and is a five-membered ring. It is a five membered cyclic
compound with one O and four C atoms.

Disaccharides
 By the loss of a water molecule, an oxide linkage is formed, which joins two monosaccharides.
 These two monosaccharides are held together by glycosidic linkage (oxide linkage) through oxygen
atom.
 The reducing groups (aldehydic or ketonic) of monosaccharides are bonded in disaccharides.
Therefore these are non-reducing sugars, e.g., sucrose.
 Whereas sugars in which these reducing groups are free, which are called reducing sugars, for
example, lactose and maltose.
Sucrose
On hydrolysis of sucrose, the equimolar mixture of D(+) glucose and D(-) fructose are formed.

 By a glycosidic linkage between C1 of a-D- glucose and C2 of b-D-fructose, these two

monosaccharides can be held together.
 Sucrose is a non-reducing sugar as the reducing groups of glucose and fructose is involved in the
formation of a glycosidic bond.
BODHI NOTES

 It is dextrorotatory, but after hydrolysis, it gives laevorotatory fructose and dextrorotatory glucose.
 BIOMOLECULES
 Since the dextrorotation of glucose (+ 52.5°) is less than laevorotation of fructose (–92.4°), hence the
mixture is laevorotatory
 Invert sugar is the product formed when there is change in the sign of rotation, from dextro (+) to
laevo (–) after the process of hydrolysis of sucrose.
Maltose

 It maltose C1 of one glucose (I) is linked to C4 of another glucose unit (II) of two a-D glucose units.
 In solution, C1 of second glucose produce a free aldehyde group, and it is a reducing sugar as it has
reducing properties.

(3) Lactose
 Lactose is found in milk so it commonly known as milk sugar.
 It is composed of b-D-galactose and b-D glucose.
 It has a linkage between C1 of galactose and C4 of glucose.
 It is considered as reducing sugar as free aldehyde group may be produced at C1 of glucose unit.

Polysaccharides
When a large number of monosaccharide units linked together by glycosidic linkages, polysaccharides
NOTES

BODHI

are formed. They generally act as the food storage or structural materials.
(1) Starch
 It is the main storage polysaccharide of plants.
 High content of starch is found in some vegetables, roots, tubers and cereals hence, it is the
most important dietary source for human beings.
 It is a polymer of alpha- glucose and consists of two components—Amylopectin and
Amylose.
Amylose
 Amylose constitutes about 15-20% of starch and is water soluble component.
BODHI NOTES

 Amylose is formed chemically formed by 200-1000 a-D-(+)-glucose units held together by

C1–C4 glycosidic linkage, forming long unbranched chain.
Amylopectin
 Amylopectin is constitutes about 80- 85% of starch and is not soluble in water.
 In it, a chain is formed by C1–C4 glycosidic linkage, while branching occurs by C1 C6 glycosidic
linkage. It is formed by the branched-chain polymer of a-D-glucose units.
 (2) Cellulose
BIOMOLECULES

 Cellulose is present mostly in plants and is the most abundant organic substance in the whole plant
kingdom. It is found mostly in the cell wall of plant cells.
 It is composed only of a-D-glucose units and is a straight chain polysaccharide , which are linked
together by the glycosidic linkage between C1 of one glucose unit and C4 of the next glucose unit.
(3) Glycogen
 In animal body glycogen is stored in the form of carbohydrates.
 Its structure is similar to amylopectin that’s why it is also known as animal starch and is
rather more highly branched.
 It is present in brain, muscles and liver. Enzymes break the glycogen down to glucose
whenever body wants glucose.
PROTEINS
 Brezeliues introduced the term protein which means first (Proteios = first).
 They are the most abundant biomolecules of the living system. Chief sources of proteins are cheese,
milk, pulses, peanuts, etc.
 They form the fundamental basis of structure and functions of life. They are present in every part of
the body.
 They are also required for maintenance and growth of body.
 It is derived from Greek word, “proteins” which means primary or of prime importance.
 All proteins are polymers of a-amino acids
Amino Acids
Amino acids are carboxylic acids having an –NH2 group. When the –NH2 group is at a-position these are
called a-amino acids.

 Amino acids can be categorized as a, b, g, d and so on, it depends on the relative position of amino
group with respect to carboxyl group. Only a-amino acids are obtained on hydrolysis of proteins.
They also can contain other functional groups. The
 property of the compond or its source are reflected by their trivial names. G
 lycine is so-called as it has a sweet taste, and tyrosine (in Greek, tyros means cheese) was first
obtained from cheese.
 Amino acids are generally represented by a 3 letter symbol, sometimes 1 letter symbol is also used.
Classification of Amino Acids
 On the basis of relative no. of carboxyl and amino groups in their molecule, they are classified as
acidic, basic or neutral.
(1) Neutral : Equal number of carboxyl and amino groups makes it neutral
(2) Basic : More number of amino than carboxyl groups makes it basic
(3) Acidic : More carboxyl groups as compared to amino groups makes it acidic.
Non-essential Amino Acids
BODHI NOTES

 Non-esseitial amino acids are defined as the type of amino acids, which can be synthesised in the
body.
Essential Amino Acids
 Essential amino acids are defined as the type of amino acids, which cannot be synthesized in the
body and must be obtained by the diet.
 BIOMOLECULES
 Their deficiency causes Kwashiorkor, a disease.
 Examples of essential amino acids include, valine, lucine, isolucine, lysine, threonil, phenyl alanine
methionyl, tryptophan, histidine and arginine.
Characteristic Features of Amino Acids
 Amino acids are generally colourless, crystalline
solids.  Cysteine and Methionine are two
 These are water-soluble and have high melting amino acids containing sulpher
point.  Glycine is the only amino acid which
 These are behave like salts rather than simple is optically inactive
amines or carboxylic acids. This behaviour is due
to the presence of both basic (amino group) and acidic (carboxyl group) groups in the same
molecule.
Zwitter Ion
 In aqueous solution, amino group can accept a proton and the carboxyl group can lose a proton,
which give rise to a dipolar ion termed as zwitter ion.

 Zwitter ion contains both positive and negative charges but is neutral in nature.
 As a-carbon atom is asymmetric; therefore, all other naturally occurring a-amino acids are optically
active, except glycine. These exist both in ‘D’ and ‘L’ forms. L-configuration is the most naturally
occurring amino acid. L-Amino acids are represented by writing the –NH2 group on the left-hand
side.
Peptide bond or Peptide Linkage
Protein is defined as a polypeptide with more
than 100 amino acid residues, having
molecular mass higher than 10,000 u.
NOTES

Classification of Proteins
BODHI

They can be classified into 2 types on the basis of their molecular shape.
(1) Fibrous Proteins
 When the polypeptide chains are held together by H and S2 bonds and run parallel, then fibre
– like structure is formed.
 Proteins are generally insoluble in water and are quite stable against a moderate change in
temperature and pH value. Ex : keratin (present in hair, wool, silk) and myosin (present in
muscles), etc.
(2) Globular Proteins
In such proteins, the polypeptide intramolecular chains get folded to give a spheroidal shape
BODHI NOTES

due to intramolecular hydrogen bonding, van der Waals forces, dipolar interaction and
disulphide bridging. These are usually soluble in water and change with a change in
temperature and pH. Ex : Insulin, ,albumins, Enzyme, haemoglobin and antibodies.

Structure of Proteins
BIOMOLECULES

 Amino acids are joined together by an amide linkage called peptide bond. Proteins are long polymers
of amino acids linked by peptide bonds (polypeptides)

Primary Structure
 Frederic Sanger gave Primary structure of Insulin for the first time.
 Proteins may have one or more than one polypeptide chains.
 Amino acids of each polypeptide in a protein are joined to each other in a specific sequence and this
sequence is termed as primary structure of that protein.
Secondary Structure
 By intramolecular H-bonding between the carboxyl and amino groups there is regular folding of the
backbone of the polypeptide chain which arises secondary structure.
 Secondary structures are found to present in two different types of structures viz. a-helix and b-pleated
sheet structure.
 By intramolecular H-bonding between — CO— and —NH— groups of the peptide bond there is
regular folding of the backbone of the polypeptide chain which aries α-helix and β-pleated sheet
structures
(a) α-Helix Structure
 α-Helix is one of the most common ways in which a polypeptide chain forms all possible
hydrogen bonds 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.
 Stabilization of an α-helical configuration by hydrogen bonding. Ex : a-keratin in skin, nails,
myosin in muscles, fibroin in silk
(b) β-pleated sheet structure
 In b-pleated sheet structure all peptide chains are stretched out to nearly maximum extension
and then laid side by side which are held together by intermolecular hydrogen bonds.
 When the size of the groups (Alkyl Group) is moderate, the polypeptide chains contract a little
to give a β-pleated sheet structure to protein molecule, as in silk protein fibroin.
Tertiary Structure
 The tertiary structure of proteins represents the folding of the polypeptide chains or folding of the
secondary structure of proteins.
 Tertiary and secondary structures of proteins are stabilise by the forces of H-bonds, disulphide
linkages, van der Waals and electrostatic forces of attraction.
 It gives rise to 2 major molecular shapes that is fibrous and globular.
Quaternary Structure
 Some of the proteins are composed of more than one polypeptide chains referred to as sub-units.
 When these subunits have spatial arrangement with respect to each other then they are termed as
quaternary structure. Ex : Haemoglobin is an aggregate of four sub-units, two identical a-chains
(having 141 Amino acid residues and two identical b-chains (having 146 Amino acid residues).
Denaturation of Proteins
BODHI NOTES

 Disruption of the native conformation of a protein will cause the protein to loose its biological activity.
This is called denaturation.
 Various changes in the surroundings of a protein such as pH, temperature, presence of salts or certain
chemical agents can disrupt the complex three-dimensional structure (conformation) of the proteins.
 Due to physical and chemical changes, the H-bonds are disturbed. Ex :(i) On boiling an egg the
albumin get coagulated. (ii) During formation of cheese from milk, the globular protein lactalbumin
becomes fibrous
ENZYMES

BIOMOLECULES
 The biological catalysts which can increase the rate of biochemical reactions even under mild
conditions of temperature and pH of living organisms are termed as enzymes.
 Enzymes are chemically similar to globular proteins.
 They are very specific for each reaction and for every substrate.
 They are usually named after the compound or group of compounds upon which they work. Ex : The
enzyme that catalyses hydrolysis of maltose into glucose is named as maltase

 Ex : Oxidoreductase enzymes are the enzymes which can catalyse the oxidation of one substrate and
simultaneously reduce another substrate.
 They are very specific in their action on substrates and each enzyme catalyses only a specific type of
reaction.
 They are active at moderate temperature (310 K), neutral pH (7) and 1 atmospheric pressure.
 The action of enzymes are inhibited by various organic and inorganic molecules called inhibitors.
 The activity of enzymes can be increased by metal ions and smaller organic molecules called
coenzymes or cofactors. For example, inorganic ions, Mg2+, Mn2+, Fe2+, Co2+, Cu2+ , organic
molecules like vitamins (thiamine, riboflavin).
VITAMINS
 They are the organic compounds which are required in small amounts in our diet but their deficiency
causes specific diseases.
 Plants can synthesise almost all of vitamins but most of the vitamins cannot be synthesised in our
body.
 Some of vitamins produce by bacteria of the gut.
 Vitamins are categorised by alphabets A, B, C, D, etc. Some of them are further termed as sub-
groups e.g. B1 , B2 , B6 , B12 , etc.
Classification of Vitamins
On the basis of their solubility in H2 O or fat they are classified into two groups.
(i) Fat Soluble Vitamins
 Vitamins which are soluble in oils and fats but not soluble in water are to be considered in
this group.
 They are vitamins A, D, E and K. These can be stored in adipose (fat storing) tissues and
liver
NOTES

BODHI

(ii) Water Soluble Vitamins

 Vitamins which are soluble in water but insoluble in fat or oils.
 Vitamin B & vitamin C are soluble in water so they can grouped together.
Vitamins sources Deficiency diseases
Vit- A (Fish liver oil, carrots)- Night blindness
Vitamin B1 Yeast, milk Beri beri
Vit-B2 Milk, egg white Cheilosis
Vit- B6 Yeast, milk Convulsions
Vit- B12 Meat, fish Pernicious anaemia
BODHI NOTES

Vit C Citrus fruits Scurvy,

Vit D Exposure to sunlight, fish and egg yolk Rickets, osteomalacia
Vit E wheat oil, sunflower oil fragility of RBCs
Vit K leafy vegetables Increased blood clotting time
NUCLEIC ACIDS
  For each and every species, every generation resembles its ancestors in many ways.
BIOMOLECULES

 For this transmission of inherent characters nucleus of a living cell is responsible, which is also
termed as heredity.
 Chromosomes are particles made up of proteins and another type of biomolecules called nucleic
acids and present in the nucleus of the cell is responsible for heredity.
 Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are two types of nucleic acids. They are
also called polynucleotides as they are long chain polymers of nucleotide.
 Nucleic acids contain the elements nitrogen, carbon, oxygen, phosphorus and hydrogen.
Chemical Composition of Nucleic Acids
The Complete hydrolysis of DNA (or RNA) yields a pentose sugar, phosphoric acid and nitrogen containing
heterocyclic compounds (called bases).
pentose sugar nitrogen containing heterocyclic compounds

In DNA molecules, the sugar moiety is b-D-2  Pyrimidine bases are uracil, thymine and
deoxyribose whereas in RNA molecule, it is b- cytosine.
D-ribose.  The purine bases found in nucleic acids are
adenine and guanine.
 DNA contains 4 bases viz. adenine (A),
guanine (G), cytosine (C) and thymine (T).
RNA also contains 4 bases, the first 3 bases
(adenine (A), guanine (G), cytosine (C)) are
same as in DNA but the fourth one is uracil
(U)
Structure of Nucleic Acids
Nucleoside N
 Nucleoside is a unit formed by the attachment of a base to 1 position of sugar. Sugar + Base =
Nucleoside
 In nucleosides, for distinguish between bases from it, the sugar carbons are numbered as 1, 2, 3 etc.
Nucleotide
 A nucleotide unit formed by the attachment of a base 1 position of sugar and attachment of
phosphoric acid with 5 position of sugar. Sugar + Base + Phosphoric acid = Nucleotide
 By phosphodiester linkage between 5 and 3 carbon atoms of the pentose sugar, nucleotides are joined
together. The formation of a typical dinucleotide.
DNA Fingerprinting
 For cracking the genetic code Dr. Khorana, Marshall Nirenberg and Robert Holley won the Nobel
Prize for Medicine and Physiology in 1968. Definition A sequence of bases on DNA is also unique
for a person and information regarding this is called DNA fingerprinting.
 DNA fingerprinting cannot be altered by any known treatment and is same for every cell.
 It is now used :
(i) For determining paternity of an individual
(ii) in forensic laboratories for identification of criminals.
(iii) for identifying racial groups to rewrite biological evolution.
(iv) for identifying the dead bodies in any accident by comparing the DNA’s of parents or children.
BODHI NOTES

Biological Functions of Nucleic Acids

 During cell division a DNA molecule is capable of self-duplication and identical DNA strands are
transferred to daughter cells.
 In the cell various RNA molecules can synthesisize proteins but for a particular protein the message
for the synthesis is present in DNA.
  DNA is the chemical basis of heredity and can be considered as the reserve of information about

BIOMOLECULES
genetic.
 Over millions of years DNA is exclusively responsible to maintain the indentification of different
species of organisms.
HORMONES
 They are the molecules that act as intercellular messengers.
 Hormones are substances or biomolecules manufactured in minute amounts in endocrine or ductless
glands. y They are carried directly into different parts by the blood stream.
 The major hormone secreting glands include the intestinal mucosa pancreas, adrenals, thyroid,
pituitary, ovaries and testes.
Types of Hormones
(1) Steroids
These type of hormones are produced by adrenal cortex and gonads (testes in males and ovaries in
females). Ex : estrogens and androgens. For various functions of the body hormones released by the
adrenal cortex play very important role.
(i) Glucocorticoids y They control the modulate inflammatory reactions, carbohydrate
metabolism and are involved in reactions to stress.
(ii) Mineralocorticoids y They control the level of excretion of salt and water by the kidney.
(2) Polypeptids — e.g. insuline and endorphins.
(3) Amino Acids Derivatives — epinephrine and norepinephrine.
Functions of Hormones
 Hormones have several functions in the body.
 In the body they help for maintaining the balance of biological activities.
 The example of this function like insulin keeps the blood glucose level within the narrow limit.
When there is rapid rise in blood glucose level in response insulin is released.
 Hormone glucagon tends to increase the glucose level in the blood. Insulin and Glucagon hormones
will regulate the glucose level in the blood.
 Growth and sex hormones play role in development and growth.
 Thyroxine formed in thyroid gland is an iodinated derivative of amino acid tyrosine.
 Lethargyness and obesity are the characteristics of hypothyroidism which is due to abnormally low
level of thyroxine.
 Hyperthyroidism is caused due to increased level of thyroxine.
 Hypothyroidism and enlargement of the thyroid gland are caused by low level of iodine in the
NOTES

BODHI

diet.By adding sodium iodide to commercial table salt (“Iodised” salt), it can be controlled.
 Hormones released by gonads are responsible for developing secondary sex characters.
 Testosterone is responsible for developing secondary male characteristics (facial hair, deep voice,
general physical constitution) and for males it is the main sex hormone.
 Likewise estradiol is the main female sex hormone. It participates in the control of menstrual cycle
and is responsible for development of secondary female characteristics.
 Progesterone is responsible for preparation of uterus for implantation of fertilised egg.
Questions
BODHI NOTES

MULTIPLE CHOICE QUESTIONS (1 MARKS)

1. α−D (+)-glucose and β−D (+)-glucose are-
(A) Anomers (B) Epimers (C) Enantiomers (D) Geometrical isomers
2. Which of the following statements about maltose is incorrect?
(A) It consists of two glucopyranose units (B) It is a disaccharide
BIOMOLECULES

(C) Glycosidic bond between C1 of one unit and C4 of the other unit (D) It is a non-reducing sugar
3. Which of the following acids is a vitamin?
(A) Aspartic acid (B) Ascorbic acid (C) Adipic acid (D) Saccharic acid
4. Which of the following statements is not true about glucose?
(A) It is an aldohexose (B) On heating with HI it forms n-hexane
(C) It is present in Pyranose form (D) It does not give 2,4-DNP test
5. The helical structure of protein is stabilized by:
(A) Peptide bond (B) Dipeptide bond (C) Hydrogen bonds (D) Vander Waal’s forces
6. The symbols D and L in the name of Carbohydrate represents
(A) Dextro rotatory nature (B) Laevo rotatory nature
(C) The relative configuration of a particular isomer (D) The optical activity of compounds
7. DNA and RNA compose of similar-
(A) Sugar (B) Purines bases (C) Pyrimidines bases (D) Both (A) and (B)
8. Which of the following is/are example(s) of denaturation of protein?
(A) Coagulation of egg white (B) Curding of milk (C) Clotting of blood (D) Both (A) and (B)
9. What are the hydrolysis products of lactose?
(A) β–D-galactose and β –D-Glucose (B) α –D-Galactose and α –D-Glucose
(C) α –D-Glucose and β –D-Fructose (D) None of these
10. Dinucleotide is obtained by joining two nucleotides together by phosphodiester linkage. Between which
carbon atoms of pentose sugars of nucleotides are these linkages present?
(A) 5’ and 3’ (B) 1’ and 5’ (C) 5’ and 5’ (D) 3’ and 3’
ANSWERS 1. A 2. D 3. B 4. D 5. C 6. C 7. B 8. D 9. A 10.A
ASSERTION REASON TYPE QUESTIONS (1MARKS)
1. Two statements are given below- one labelled Assertion (A) and the other labelled Reason (R).
ASSERTION – Vitamin C can’t be stored in our body.
REASON – Vitamin C is water soluble and is excreted from the body through urine.
(a) A and R both statements are correct and R is the correct explanation of A.
(b) A and R both statements are correct and R is not the correct explanation of A.
(c) A is correct statement but R is not the correct statement.
(d) A is incorrect statement but R is the correct statement.
2. Two statements are given below- one labelled Assertion (A) and the other labelled Reason (R).
ASSERTION – Proteins are polymers of alpha amino acids connected by peptide bonds.
REASON – A tripeptide contains 3 amino acids linked by 3 peptide bonds.
3. Two statements are given below- one labelled Assertion (A) and the other labelled Reason (R).
ASSERTION – Change in pH and heating leads to denaturation of proteins.
REASON – Change in pH and heating cause loss of biological activity of proteins.
4. Two statements are given below- one labelled Assertion (A) and the other labelled Reason (R).
ASSERTION – Adenine and Guanine are the purines present in both nucleic acids.
REASON – Thiamine and Uracil are the pyrimidine present in DNA.
5. Two statements are given below- one labelled Assertion (A) and the other labelled Reason (R).
ASSERTION – Amylopectin is water soluble and contributes 15-20% of starch.
BODHI NOTES

REASON – Amylopectin has C1-C4 & C1-C6 glycosidic linkages.

ANSWERS 1.A 2.B 3.A 4.C 5.D
VERY SHORT ANSWER QUESTIONS (1M)
1. What is the basic structural difference between glucose and fructose? A. Glucose has aldehyde group
whereas fructose has keto group.
2. Name the carbohydrate used as storage molecule to store energy in animals? A. Glycogen
3. Name the vitamin whose deficiency cause pernicious anemia? A. Vit B12

BIOMOLECULES
4. Write down the vitamin which is responsible for the coagulation of blood? A. Vit K
5. Give one example each for Fibrous protein and Globular protein. A. Fibrous protein – Keratin, Globular
protein – Insulin
6. What type of linkage is responsible for the formation of proteins? A. Peptide linkage.
7. Name the unit formed by the attachment of a base to 11 positions of sugar. A. Nucleoside
8. Write the products obtained after hydrolysis of DNA.
A. Pentose sugar, phosphoric acid and Nitrogen containing heterocyclic compounds as bases.
9. Name the base that is found in nucleotide of RNA only ? A. Uracil
10. Name a) A major sex hormone produced in males b) The main female sex hormone
A. a) Testosterone b) Estradiol
SHORT ANSWER QUESTIONS TYPE – 1 ( 2M)
1. What is the difference between nucleotide and nucleoside?
A. Nucleoside contains ribose or deoxyribose sugar and heterocyclic base. Nucleotide contains phosphoric
acid residue along with heterocyclic base and pentose sugar.
2. Name a water-soluble vitamin which is a powerful antioxidant? Give one of its sources. A. Vit C, citrus
fruits like orange, lemon etc.
3. Write 2 differences between RNA and DNA. A. RNA – a) It has ribose sugar with adenine, uracil,
cytosine, guanine as heterocyclic bases. b) It is single helix. DNA – a) It has deoxyribose sugar along with
adenine, thiamine, cytosine, guanine as heterocyclic bases. b) It is double helix.
4. What are the two types of secondary structure of proteins? How will you differentiate between them? A.
Alpha – helix and Beta pleated helix structure. Those polypeptide chains stabilized by intramolecular
hydrogen bonds are alpha helix structure. Beta pleated structure of proteins are stablilised by intermolecular
hydrogen bonding.
5. What are polysaccharides? Give two examples. A. Those carbohydrates which on hydrolysis give large
number of monosaccharides. Eg:- Starch, Cellulose.
SHORT ANSWER QUESTION TYPE – 2 ( 3M)
1. Differentiate between a) Amylose and Amylopectin b) Peptide linkage and Glycosidic linkage c)
Fibrous proteins and Globular proteins.
2. Define the following with suitable examples a) Oligosaccharides b) Denaturation of proteins c)
Vitamins
3. What are essential and non – essential amino acids? Give two examples of each.
4. Write chemical reactions to show that open structure of D-glucose contains the following a) Straight
chain b) 5 alcohol groups c) Aldehyde as carbonyl group
NOTES

BODHI

5. a) Why Vit C cannot be stored in our body? b) Write the name of Vitamin whose deficiency causes
bone deformities in children. c) Deficiency of which Vitamin cause night blindness.
LONG ANSWER QUESTIONS (5M)
1. Give reasons for the following observations. a) Amino acids behave like salts rather than simple
amines or carboxylic acids. b) Amino acids show amphoteric behavior. c) The two strands of DNA
are complementary to each other. d) Pentaacetate of glucose does not react with hydroxyl amine. e)
Starch and cellulose both contain glucose units as monomers yet they are structurally different.
2. a) Which sugar is called invert sugar? Why is it called so? b) How can reducing and non-reducing
BODHI NOTES

sugars be distinguished? Mention the structural feature characterizing reducing sugars