BIOMOLECULES NCERT POINTS

• All the elements present in a sample of earth’s crust are also present in a sample
of living tissue
• Relative abundance of carbon and hydrogen with respect to other elements is
higher in any living organism than in earth’s crust

CHEMICAL ANALYSIS
• Take any living tissue (a vegetable or a piece of liver, etc.) and grind it in
trichloroacetic acid (Cl 3 CCOOH) using a mortar and a pestle → thick slurry →
strain this through a cheesecloth or cotton we would obtain two fractions→ One
is called the filtrate or the acid-soluble pool, and the second the retentate or
the acid-insoluble fraction
 Filtrate/acid soluble pool Retentate/acid insoluble pool
Micro molecules, cytoplasmic Macromolecules, organic compounds
composition, organic and inorganic and cell organelles are found
compounds are found

All the carbon compounds that we get from living tissues can be called ‘biomolecules’
However, living organisms have also got inorganic elements and compounds in them

• Destructive experiment to know the inorganic elements and compound present in

the living organism:
weighs a small amount of a living tissue (say a leaf or liver and this is called wet
weight) and dry it→ water, evaporates→ gives dry weight→ tissue is fully
burnt→ all the carbon compounds are oxidised to gaseous form (CO2 , water
vapour) and are removed→ remaining is called ‘ash’ it contains inorganic
elements (like calcium, magnesium etc)
• Therefore elemental analysis gives elemental composition of living tissues in the
form of hydrogen, oxygen, chlorine, carbon
• Analysis of compounds : gives an idea of organic and inorganic constituents
present in living tissue
• From a chemistry point of view, one can identify functional groups like
aldehydes, ketones, aromatic compounds, etc. But from a biological point of view,
we shall classify them into amino acids, nucleotide bases, fatty acids etc
Practice question

1. to perform a chemical analysis which of the following chemicals is primarily used to grind
a living tissue
a) Cl3 CCOOH c) Cl2 CCOOH
b) Cl3 COOH d) Cl 2CCOOH2
2. Q2) select the correct match among the following:
Element Earth’s crust Human body
Oxygen 46.6 65.0
Sodium 2.8 2.0
Magnesium 0.1 2.1
Silicon 27.7 18.5
3. All the carbon compound that we get from living tissue can be called
a. micro molecules c) macromolecules
b. carbohydrates d) biomolecules
4. A: ash contains inorganic elements like Ca, Mg etc

B: inorganic compound like sulphate, phosphate etc are seen in acid soluble fraction

a) A and B correct b) A and B incorrect

c) Only A correct d) Only B correct

Q5) inorganic compound found in human body

a) NaCl,CaCO3, SO42-, PO43-,NaCl

b) C6H12O6, SO42-, PO43-,NaCl

c) Na+,K+,NaCl

d) none of the above

Q6) to initiate analysis of chemical composition we can take any living tissue and grind it in acid like

a) Palmitic acid b) stearic acid

c)trichloroacetic acid d) trihydroxpropane

Q7) select the incorrect one

a) with respect to other elements C and H is higher in any living organism w.r.t earths crust

b) All the elements present in a sample of earths crust are also present in a sample of living tissue

c) water is the least abundant chemical in living organisms

d) percent weight of calcium in earth’s crust is 3.6

PRIMARY AND SECONDARY METABOLITE

• Thousands of organic compounds including amino acids, sugars: Primary
metabolite
• Animals primary metabolites are present
• In plant, fungal and microbial cells thousands of compounds other than primary
metabolites, e.g. alkaloids, flavonoids, rubber, essential oils, antibiotics, coloured
pigments, scents, gums, spices called secondary metabolites
• primary metabolites: play known roles in normal physiologial processes
• secondary metabolite: many of them are useful to ‘human welfare’ (e.g., rubber,
drugs, spices, scents and pigments), ecological importance

CARBOHYDRATES

• Most abundant organic molecules in nature

• Primarily composed of Carbon, Hydrogen, Oxygen
• Hydrates of carbon
• Polyhydroxy aldehydes or ketones
• Termed as sugar is applied to carbohydrates soluble in water and sweet in taste

most abundant
dietary source of
energy 4Kcal/g

utilized as raw precursors for

material in paper, many organic
textile, alcohol compunds (fats,
industries amino acids)

functions of
carbohydrates

present in cell
storage form of
mambrane as
energy
glycoprotein

structural
component like
cellulose fibre ,
exoskeleton of
insects, cell wall of
organisms
CLASSIFICATION OF CARBOHYDRATES(based on number of sugar units):
often referred as saccharides/sugar
MONOSACCHARIDES OLIGOSACCHARIDES POLYSAACHARIDES
-Simplest carbohydrates -oligo: few -polymer of
-Cn(H2O)n -contain 2-10 monosaccharides monosaccharides
-cannot be further a) disaccharides: Cn(H2 O)n-1 -tasteless
hydrolysed e.g, a) homopolysaccharides
a) trioses: glyceraldehyde, Maltose: glucose+ glucose contain monosaccharide
dihydroxyacetone occurs in germinating seeds like units of single type
b) tetroses: Erythrose barley starch, glycogen, inulin,
c) pentoses: а-D glucose(1->4)a-D-glucose cellulose
ribose, deoxyribose b) heteropolysaccharides: 2
or more different types of
units
sucrose: glucose+ fructose heparin, chondroitin
-cane sugar sulphate
d) hexoses: aDglucose(1->2)ßDfructose

lactose: glucose+ galactose

-milk sugar
ßDgalactose(1->4)ßDglucose

e) heptoses: sedoheptulose

NOTE:
• D and L isomers: mirror images of each other, position of H and OH on the second
last carbon atom
-OH on right D series sugar
-OH on left L series sugar

• Glucose and galactose are epimers

• Anomers
 • Derived monosaccharides :
-N acetyl glucosamine

• Reducing and non-reducing sugar:

Reducing property is attributed to free aldehyde or keto group of anomeric
carbon, tests for reducing action of sugars include Benedict’s, Fehling’s etc

-Found in acid insoluble pool

-long chain of sugars, monosaccharides are building block
-they are cotton thread
-cellulose: homopolymer, polymer of only one monosaccharides, doesn’t
contain helices and hence cant hold I2, plant cell wall made of it
-starch: store of house of energy in plants, forms helical secondary
structures, can hold I2 molecules in the helical portion;starch-I2 is bljue in
colour
-glycogen: present in animals, branched
-inulin: polymer of fructose
-in polysaccharides: right end is REDUCING and left end is NON-
REDUCING
-Chitin: most complex, modified polysaccharides, N acetyl glucosamine,
exoskeleton of arthropods, fungi cell wall
AMINO ACIDS

• organic compounds, contains amino group and an acidic group as substituents on

the same carbon i.e., the α-carbon called as α-amino acids
• amino group: basic, carboxyl group: acidic in nature
• general structure of amino acid :
 The amino acid except glycine posses four distinct groups held by alpha carbon
thus all amino acids have optical isomers

Proteins are composed of L alpha amino acids

• substituted methanes
• there are four substituent groups occupying the four valency positions:
hydrogen, carboxyl group, amino group and a variable group designated as R
group
• Classification of amino acids:
20 amino acids found in proteins are divided into seven distinct groups
Amino acid with aliphatic side chains:
1) glycine Gly

2) Alanine Ala

Valine Val

Leucine Leu

Isoleucine Ile
Amino acids conitaning hydroxyl groups
Serine Ser

Threonine Thr

Tyrosine Tyr

Sulfur containing amino acids

Cysteine Cys

Methionine Met

Acidic amino acids and their amides

Aspartic Asp
acid

Asparagine Asn

Glutamic Glu
acid

Glutamine Gln
Basic amino acid
Lysine Lys

Arginine Arg

Histidine His

Aromatic amino acid

Phe
Phenylalanine

Tyrosine Tyr

Tryptophan Trp

Imino acids
Proline Pro
 TYPES ON NUTRITION BASIS:
ESSENTIAL/INDISPENSIBLE AMINO NON-ESSENTIAL/ DISPENSIBLE
ACID
Amino acid which cant be synthesised by Synthesised by body hence need not
the body, need to be supplied through to be consumed in the diet
diet Glycine
Phenylalanine Alanine
Valine Serine
Tyrosine Cysteine
Threonine Aspartate
Isoleucine Asparagine
Methionine Glutamate
Histidine Glutamine
Arginine Tyrosine
Lysine Proline
Note: arginine and histidine are semi
essential

• Based on the nature of R group there are many amino acids

• There are only 20 amino acid present in proteins few examples:

• The chemical and physical properties of amino acids are essentially of the amino,
carboxyl and the R functional groups
• Acidic (e.g., glutamic acid,aspartic acid ), basic (histidine, arginine,lysine) and
neutral (valine) amino acids
• Aromatic amino acids (tyrosine, phenylalanine, tryptophan)
• In solutions of different pHs, the structure of amino acids changes

Q1) select the correct option

a) The amino acids are substituted methane
b) based on the nature of carboxylic group there are many amino acids
c) when R group is methyl group, the amino acid is alanine
1) a and b are correct
2) b and c are correct
3) a,b and c are correct
 4) a and c are correct
Q2) Based on number of amino and carboxyl groups there are
a) Acidic amino acid
b) basic amino acid
c) neutral amino acid
d) All
Q3) Non -aromatic amino acid among the following
a) tyrosine
b) lysine
C) phenylalanine
d) tryptophan
True/ false

1) secondary metabolite have identifiable function and play known roles in normal physiological processes
2) alkaloids like morphine and vinblastine are secondary metabolite obtained from plants
3) curcumin and ricin are potent drugs
4) secondary metabolites are produced by plants for their growth and development
5)the organic molecules in the caid soluble fraction with the exception of lipids are polymeric substances
6) the acid insoluble pool represents roughly cytoplasmic composition
7) alanine is a basic amino acid
8) tryptophan is an aromatic amino acid whereas tyrosine is an acidic amino acid
9) exoskeleton of arthropods have a complex polysaccharides called chitin
10) plant cell wall are made of chitin
11) cellulose and glycogen are primary metabolite
12) cysteine is a polymer of N acetyl glucosamine
13) insulin is a nitrogen containing complex polysaccharides
14) if the elemental analysis is done on a sample of human cheeks cells we observe the list of elements that are also
present in earths curst. It is observed that there is certain differences in the percentage of respective elements
Choose the correct differences among the following
a) Relative abundance of C and Calcium w.r.t other elements is higher in earths crusts than human body
b) There is a significant high amount of N and silicon in both
c) Relative abundance of C and H w.r.t other elements is higher in human body than in earth’s crusts
d) Silicon and sulphur are least abundant in earth’s crusts and human body respectively
15) A dry living tissue is burnt fully and examined later on for the presence of elements in it. All of the following can be
found in the remains except
a) calcium
B) magnesium
c) carbon dioxide
d) sulphur
16) amino acids “X” can be thought of as a hydroxylated version of alanine. It is much more reactive than alanine
Select the correct option for “X”
a) proline
b) tryptophan
c) serine
d) glycine
17) amino acids are substituted methane there are 20 types of amino acids and all of them contain a single asymmetric
carbon except
a) glycine b) proline
c) lysine d) cysteine
18) select the acidic amino acid among the following
a) palmitic acid b) glutamic acid
c) uridylic acid d) thymidylic acid
19) select the correct statement
a) glucose is the monomeric unit of the structural polysaccharides of arthropods
b) deoxyribose is a hexose sugar present in DNA
c) structural formula of glucose, ribose and fructose sugar is same
d) six membered nitrogen ring and five membered nitrogen ring are joined to form a purine
20) which among the following is a heteropolymer
a) cellulose b) starch
c) collagen d) glycogen
21) A: during elemental analysis of a tissue the retentate represents rough cytoplasmic composition
B: the macromolecules from the cytoplasm and organelles become the acid insoluble fraction
a) both the statements A and B are correct
b) both the statements are incorrect
c) only A is correct
d) only B is correct
22) arrange the composition of substances in cells
a) Proteins Water Carbohydrates Lipids Nucleic acid
b) Water carbohydrates Nucleic acids Proteins Lipids
c) Water protein Nucleic acid Carbohydrates Lipids
d) Protein Carbohydrate Nucleic acid Lipids Water
23) match the items w.r.t secondary metabolites
i) cellulose a) provides yellow/ orange color to plants, algae
ii) carotenoids b) structural component of plant cell wall
iii) abrin c) an opiate alkaloid
iv) morphine d) toxic protein obtained from a plant
A) i-b,ii-a,iii-d,iv-c
b) i-b, ii-d, iii-c, iv-a
c) i-b,ii-a,iii-c,iv-d
d) i-d, ii-b, iii-a, iv-c
24) the right end of inulin chain is ______ and the left end is ____
a) reducing, non-reducing
b) non-reducing, non-reducing
c) reducing, reducing
d) non-reducing, reducing
25) the cell wall of okara plant is made up of cellulose. The variant of this present in plants that acts as store house of
energy
a) glycogen b) glucosamine
c) chitin d) starch

LIPIDS
• Water insoluble
• They could be simple fatty acids, glycerol which is trihydroxy propane, both
glycerol and fatty acids
• Fatty acid: carboxyl group attached to an R group, The R group could be a
methyl (–CH3 ), or ethyl (–C2H5 ) or higher number of –CH2 groups (1 carbon to
19 carbons)
a) saturated fatty acid(single bond): Palmitic acid (16 carbons including
carboxylic carbon)
b) Unsaturated fatty acid(double bond): Arachidonic acid (20 carbon including
carboxylic carbon)
• fatty acids are found esterified with glycerol, it can be monoglyceride,
diglyceride, triglyceride
• Lipids are also called fats and oils based on melting point. Oils have lower
melting point (e.g., gingely oil) and hence remain as oil in winters
• Phospholipids/ phosphorylated lipid -lecthin
 Some tissues especially the neural tissues have lipids with more complex
structures
Q1) A: Palmitic acid has 16 C atoms excluding carboxyl carbon
B: Arachidonic acid has 20 C atom excluding Carboxyl carbon
1) both are correct
2) both are false
3) A is true
4) B is true

Nucleotide(monomer of nucleic Acid, found in acid soluble pool)

• nitrogen bases – adenine, guanine (purine, 9 membered heterocyclic ring)
cytosine, uracil, and thymine (pyrimidine, 6 membered heterocyclic ring)
• Nucleosides: nitrogen base+ pentose sugar
- Adenosine, guanosine,thymidine, uridine and cytidine
• Phosphate group esterified with nucleosides: Nucleotide
-Adenylic acid, thymidylic acid, guanylic acid, uridylic acid and cytidylic acid
• Nucleic acid (DNA and RNA made up of nucleotides)
• DNA and RNA : genetic material

Q1)concanvalin A belongs to which group of seconadry metabolite

1)Alkaloids
2) terpenoids
3) polymeric substances
4) lectins
Q2) choose pair of toxins:
a)concanvalinA, curcumin
 b) rubber, gums
c) ricin, abrin
d) morphine, diterpenes
BIOMARCOMOLECULES
MICROMOLECULES MACROMOLECULES
-molecular weight range: 18 to 800 -range of ten thousand daltons and
daltons above
-found in acid soluble pool -found in acid insoluble pool
-cytoplasmic composition -proteins, nucleic acids,
polysaccharides and lipids, organelles
Except lipid other three are
macromolecule
• Lipids are not strictly macromolecules

Q) feature common to all the compounds found in the acid soluble pool
a) molecular weight up to 18D
b) molecular weight from 18 to 800 D
c) molecular weight from 18 to 1800d
d) molecular weight from 10,000d and above

PROTEIN
• Polypeptides, polymer of amino acid linked with peptide bonds
• Heteropolymer
• dietary proteins are the source of essential amino acids, non essential made by
body
• Collagen is the most abundant protein in animal world and Ribulose bisphosphate
Carboxylase-Oxygenase (RuBisCO) is the most abundant protein in the whole of
the biosphere

POLYSACCHARIDES
• Macromolecules, found in acid insoluble pool, polymer of sugars/long chains of
sugars
• Cellulose: homopolysaccharides, structural polysaccharide, made up of glucose
unit, unbranched, don’t give IODINE test, present in plant cell wall, Paper made
from plant pulp and cotton fibre is cellulosic, cotton fibres
• Starch: storage polysaccharide of plant, homopolysaccharide, polymer of
glucose, helical and branched, gives iodine test
• Glycogen: storage polysaccharides of animals, homopolysaccharide, polymer of
glucose, helical and branched, gives iodine test
• Inulin: polymer of fructose, storage polysaccharide
• Chitin: polymer of N-acetyl glucosamine(NAG), exoskeleton of arthropod, fungi
cell wall
• In a polysaccharide chain (say glycogen), the right end is called the reducing end
and the left end is called the non-reducing end

NUCLEIC ACID
• Macromolecules, found in acid insoluble pool, polymer of
nucleotides,polynucleotides
• A nucleotide has three chemically distinct components:One is a heterocyclic
compound, the second is a monosaccharide and the third a phosphoric acid or
phosphate
• Heterocyclic compounds in nucleic acids are the nitrogenous bases named
adenine, guanine, uracil, cytosine, and thymine
• Adenine and Guanine are substituted purines while the rest are substituted
pyrimidines
• heterocyclic ring is called as purine and pyrimidine
• The sugar found in polynucleotides is either ribose (a monosaccharide pentose)
or 2’ deoxyribose
• A nucleic acid containing deoxyribose is called deoxyribonucleic acid (DNA) while
that which contains ribose is called ribonucleic acid (RNA)

• In a nucleic acid a phosphate moiety links the 3’-carbon of one sugar of one
nucleotide to the 5’-carbon of the sugar of the succeeding nucleotide The bond
between the phosphate and hydroxyl group of sugar is an ester bond. As there is
one such ester bond on either side, it is called phosphodiester bond
• wide variety of secondary structures
• Watson -crick model :
- DNA exists as a double helix
-two strands of polynucleotides are antiparallel
-backbone is formed by the sugar-phosphate-sugar chain
-A=T;C=G
-There are two hydrogen bonds between A and T and three hydrogen bonds
between G &C
-Each strand appears like a helical staircase
-each step of ascent, the strand turns 36°
-One full turn of the helical strand would involve ten steps or ten base pairs
-The pitch would be 34Å
-This form of DNA:B -DNA
Q) There are ___ hydrogen bonds between adenine and thymine and
_____hydrogen bond between guanine and cytosine DNA molecule
a)2 and 3 d) 4 and 5
b) 4 and 3
c) 3 and 2