It contains content about different types of biomolecules and their utilisation in our life. Cabohydtates are source of energy and obtained by various source. Fats and protein both are also essential for our life.
Biomolecules are molecules produced by living organisms or are
compounds that occur naturally in plants and animals.
They could be large macromolecules or smaller molecules such as
primary or secondary metabolites. Exp.
Proteins (Amino acids)
Nucleic acids ( DNA & RNA)
Polysaccharides ( Starch, Callulose, Glycogen etc)
Lipids (Fatty acids, Glycerols)
Carbohydrates are good source of energy. Carbohydrates (polysaccharides) are long
chains of sugars.
Monosaccharides are simple sugars that are composed of 3-7 carbon atoms.
They have a free aldehyde or ketone group, which acts as reducing agents and are
known as reducing sugars.
Disaccharides are made of two monosaccharides. The bonds shared between two
monosaccharides are the glycosidic bonds.
Polysaccharides are polymers of monosaccharides. They are un-sweet and complex
They are insoluble in water and are not in crystalline form. - Example: glucose,
fructose, sucrose, maltose, starch, cellulose etc
eg. Aldoses, Ketoses
eg. Maltose, Sucrose,
4. Chemical nature of carbohydrate
a) Chemical nature: A carbohydrate is a biomolecule consisting of carbon (C),
hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1
(as in water) and thus with the empirical formula Cm(H2O)n (where m may be different
Carbohydrates are divided into four major groups
i) Monosaccharides: Aldoses: Aldose contain aldehyde as one of their functional
groups e.g. glucose, galactose.
Ketoses: Ketoses contain ketone as one of their functional groups e.g. fructose,
Classification based on the number of carbon atoms: 1 Triose (3C, glyceraldehyde);
2. Tetrose (4C, Erythrose), Pentose (5C, Xylose), Hexose (6C, Glucose, Fructose),
Heptose (7C, Glucoheptose).
Carbohydrates contain 2n isomers (Where n=asymmetric carbon atoms).
D and L isomerism: Spatial position of second last position of hydroxyl group decides
D (right side) and L (left side) configuration of carbohydrates as shown in example.
Epimers: an epimer is a stereoisomer that differs in configuration at any single
stereogenic center. E.g Glucose and mannose are epimers at C2 while glucose and
galactose are epimers at C4.
Anomers are cyclic monosaccharides or glycosides that are epimers, differing from
each other in the configuration of C-1 if they are aldoses or in the configuration at C-2
if they are ketoses. The epimeric carbon in anomers are known as anomeric carbon or
Mutarotation: Inter conversion of of α and β anomers of glucose in solution along with
the change in their optical activity are called mutarotation.
7. Reactions of Monosaccharides
Tautomerism: The process of shifting a hydrogen atom from one carbon atom to
another to produce enediols is known as tautomerization.
Reducing properties: The reducing property is due to presence of free aldehyde or
ketone group of anomeric carbon. There are many test to employed to identify the reducing
action of sugars. These include Benedict’s, Fehling’s, Barfoed’s test.
8. Oxidation: Oxidation of aldehyde group(CHO COOH) results in the formation
of gluconic acid.
Oxidation of terminal alcohol group (CH2OH COOH) leads to the formation of
Reduction: When treated with reducing agents such as sodium amalgam, aldehyde
or keto group of monosaccharide is reduced to corresponding alcohol.
Dehydration: When treated with concentrated sulfuric acid, monosaccharides
undergo dehydration with an elimination of 3 water molecules. Thus hexoses give
hydroxymethyl furfural and pentoses give furfural on dehydration.
Osazone formation: Phenylhydrazine in acetic acid, when boiled with reducing
sugars, forms osazone in a reaction.
Formation of esters: The alcoholic groups of monosaccharides may be esterified
by non-enzymatic or enzymatic reactions. Eg. Glucose-6-phosphate and glucose-1
Glycosides: Glycosides are formed when the hemiacetal or hemiketal hydroxyl
group ( of anomeric carbon) of a carbohydrate reacts with a hydroxyl group of another
9. Disaccharides: A disaccharide (also called a double sugar or bivose) is the sugar formed when
two monosaccharides (simple sugars) are joined by glycosidic linkage. Like monosaccharides,
disaccharides are soluble in water.
Three common examples are sucrose (in cane sugar), lactose (in milk), and maltose (in wheat)
which have common formula C12H22O11
Reducing sugar: A reducing sugar is any sugar that is capable of acting as a reducing agent
because it has a free aldehyde group or a free ketone group.
All monosaccharides are reducing sugars, along with some disaccharides (lactose, maltose),
oligosaccharides, and polysaccharides.
Non-reducing sugars do not have an OH group attached to the anomeric carbon so they cannot
reduce other compounds eg. Sucrose
Sucrose is also called invert sugar because levo rotation of fructose (hydrolysis product) is
greater then dextro-rotation of glucose after hydrolysis. The process is called inversion.
10. Sucrose : It is commercially produced by sugar cane and sugar beet. It is made up of α –D-
glucose and β-D-fructose.
Maltose: It is produced by the course of digestion of starch by the enzyme amylase.
Maltose is composed of two α –D-glucose unit held together by α-(1 4) glycosidic
Lactose: It is more commonly known as milk sugar. Lactose is composed by β-D-
galctose and β–D-glucose.
Starch is the carbohydratereserve of plants which is the most important dietary source for
higher animals like man. It is mainly found in cerels, roots, tubers, vegetables etc. Starch is
homopolymer composed of D-glucose units held by α-glycosidic bonds.
Starch consist of two polysaccharide components water soluble amylose (15-20%) and a water
insoluble amylopectin (80-85%).
Chemically amylose is a long unbranched chain with 200-1000 D-Glucose unit held by α-(1 4)
Amylopectin is branched chain of α-1 6) glycosidic bonds at the branching points and
α-(1 4) linkages every where.
12. Lipids are composed of long hydrocarbon chains.
Lipid molecules hold a large amount of energy and are energy storage molecules.
Lipids are generally esters of fatty acids and are building blocks of biological
Most of the lipids have a polar head and non-polar tail.
Fatty acids can be unsaturated and saturated fatty acids.
Exp. oils, fats, phospholipids, glycolipids, etc.
Eg. Oils & waxes Complex lipid eg.
eg. Glycerols, fatty acid
Fats & Oil Waxes
Phospholipids Glycolipids Steroids Terpenes Carotenoids
13. 1. Simple lipid: Esters of fatty acids with alcohol. They are mainly of two types.
a.) Fats and Oils: These are esters of fatty acid with glycerol. The difference between fats and oil
is only physical. Thus, oil is liquid while fat is solid at room temperature.
b.) Waxes: Esters of fatty acids with alcohols other than glycerol. Cetyl alcoholvis the most
commonly found in waxes.
2. Complex or compound lipids : Esters of fatty acids with alcohol containing additional groups
such as phosphate, nitrogenous base, carbohydrate, protein etc.
a.) Phospholipids: Lipid containing phosphoric acid and freuently nitrogenous base.
i.) Glycerophospholipids: These phospholipid contain glycerol as the alcohol e.g. Lecithin and
ii) Sphingophospholipids: Sphingosine is the alcohol in this group of phospholipids e. g.
b.) Glycolipids: These lipids contain a fatty acid, carbohydrate and nitrogenous base. The alcohol
is sphingosine, hence they are called as glycosphingolipids. E.g. Cerebrosides, gangliosides
Eg Lipids - Fatty acids - Oleic acid, Linoleic acid, Palmitoleic acid, Arachidonic acid.
Fats and Oils - Animal fats - Butter, Lard, Human fat, Herring oil
Plant oils - Coconut oil, Corn, Palm, Peanut, Sunflower oil.
Waxes - Spermacti, Beeswax, Carnauba wax.
Phospholipids - Lecithins, Cephalins, Plasmoalogens, Phosphatidyl inositols, Sphingomyelins. - Glycolipids - Kerasin,
Phrenosin, Nervon, Oxynervon.
Steroids – Cholesterol.
Terpenes - Monoterpenes, Sesquiterpenes, Diterpenes, Triterpenes. - Carotenoids - Lycopene, Carotenes, Xanthophylls.
Oleic acid Linolenic acid
FATTY ACIDS: Fatty acids are carboxylic acids with hydrocarbon side chain. It is classified into 2
a. Saturated b. Unsaturated fatty acids
Essential fatty acids - Two fatty acids are dietary essentials in humans
(i) Linoleic acid, which is the precursor of arachidonic acid, the substrate for prostaglandin
(ii) α-linolenic acid is the precursor for growth and development - Essential fatty acid deficiency
can result in a scaly dermatitis, as well as visual and neurologic abnormalities.
16. Properties of triacyglycerols
1. Hydrolysis : Triacylglycerols undergo stepwise enzymatic hydrolysis to finally liberate free fatty
acids and glycerol. The process of hydrolysis, catalyzed by lipase is important for digestion of fat.
2. Saponification : The hydrolysis of triacylglycerols by alkali to produce glycerol and soap is
known as saponification.
Triacylglycerol + 3NaOH Glycerol + 3R-COONa (soaps)
3. Rancidity : Rancidity is the term used to represent the deterioration of fats and oils resulting
is an unpleasant taste. Fats containing unsaturated fatty acids are more susceptible to rancidity.
Rancidity occurs when fats and oils are exposed to air, moisture, light, bacteria etc. Oxygen is
required for oxidative rancidity which occurs through the formation of intermediates, namely
Phospholipid: These are complex lipids containing phosphoric acid, in addition to fatty acids,
nitrogenous base and alcohol. There are two types of phospholipids
1. Glycerophospholipids that contain glycerol as the alcohol.
2. Sphingophospholipids that contain sphingosine as the alcohol.
Glycerophospholipids are the major lipids that occur in biological membrane. They consist
of glycerol-3-phosphate esterified at its C1 & C2 with fatty acids.
Steroids: These are compounds containing cyclic steroids nucleus namely
cyclopentanophenanthrene. It consists of a phenanthrene nucleus ( rings A, B,& C) to
which a cyclopentane ring D is attached.
Cholesterol: Cholesterol is exclusively found in animals and is the most abundant animal sterol.
It is widely distributed in all cells and is major component of cell membrane & lipoprotein.
The stucture of cholesterol C27H46O. It has one hydroxyl group at C3 & C6.
17. Biological Role of Lipids
1. Food material: Lipids provide food, highly rich in calorific value. One gram lipid produces
9.3 kilocalories of heat.
2. Food reserve: Lipids provide are insoluble in aqueous solutions and hence can be stored
readily in the body as a food reserve.
3. Structural component: Lipids are an important constituent of the cell membrane.
4. Heat insulation: The fats are characterized for their high insulating capacity. Great quantities
of fat are deposited in the subcutaneous layers in aquatic mammals such as whale and in
animals living in cold climates.
5. Fatty acid absorption: Phospholipids play an important role in the absorption and
transportation of fatty acids.
6. Hormone synthesis: The sex hormones, adrenocorticoids, cholic acids and also vitamin D are
all synthesized from cholesterol, a steroidal lipid.
7. Vitamin carriers: Lipids act as carers of natural fat-soluble vitamins such as vitamin A, D and E.
Cholesterol is an yellowish crystalline solid. It gives several reactions like Salkowski, Libermann’s
buchard reactions and Zak’s test.
It is insoluble in water and soluble in organic solvents such as chloroform, benzene etc.
18. Nucleic acids (DNA and RNA) are unquestionably the top l l evel molecules because
they store our genetic information.
They are polymers of nucleotides, which themselves are made of three parts—a
heterocyclic base, a sugar, and a phosphate ester.
The base along with the sugar
forms a nucleoside, which combined
with the phosphate group forms the
Phosphates are key compounds in nature because they form useful stable linkages
between molecules and can also be built up into reactive molecules by simply
multiplying the number of phosphate residues.
The most important of these nucleotide is also one of the most important molecules
in nature—Adenosine triphosphate.
19. Components of Nucleic Acids
Nucleic acid contains five bases, two sugars, and one phosphate groups. The bases are
monocyclic pyrimidines or bicyclic purines and are all aromatic. The two sugars are
ribose (RNA) and 2-deoxy ribose (DNA).
20. Proteins are large biomolecules, or macromolecules, consisting of one or more long
chains of amino acid residues.
Proteins are known as building blocks of life.
Proteins are the most abundant intracellular macro-molecules.
They provide structure, protection to the body of multicellular organism in the form
of skin, hair, callus, cartilage, ligaments, muscles, tendons.
Proteins regulate and catalyze the body chemistry in the form of hormones,
enzymes, immunoglobulin’s etc.
Functions of proteins
1. Enzymes are proteins which are catalyzed rate of reactions.
2. They help in transportation and storage of materials like
haemoglobin, myoglobin, albumin etc.
3. Actin and myosin are contractile proteins in muscles.
4. They act as protective in like keratins.
5. They act as supportive like collagen.
6. They act as defensive function like immunoglobins.
22. Structure of proteins
Primary structure of proteins:
Each protein has unique sequence of aminoacids which is determined by the genes contained
in DNA. Aminoacids are held together in a protein by covalent bonds or linkages. These bonds
are rather strong and serve as the cementing material between the individual amino acids.
Formation of peptide bond: When the amino group of an aminoacid combines with carboxyl
group of an aminoacid combines with the carboxyl group of another aminoacid, a peptide
bond is formed.
Dipeptide will have two aminoacids. Peptide containing more than 10 aminoacids are
reffered to as polypeptide.
Characteristics of a peptide bonds: The peptide bond is rigid & planar with partial double
bond in character. It generally exist in trans configuration. Both C = O & -NH groups of peptide
bonds are polar and are involved in hydrogen bond. Conventially peptide chains are written
with free amino end ( N-terminal residue) at the left and the free carboxyl end ( C- terminal
residue) at the right. The aminoacid sequence is read from the N-terminal end to C-terminal
23. Dimension of polypeptide : The dimension of an fully extended polypeptide chains are
Determination of primary structure: The primary structure comprises the identification of
constituent aminoacids with regards to their quality, quantity and sequence in a protein
structure. It involves 3 stages
1. Determnation of amino acid composition
2. Degradation of protein or polypeptide into smaller fragments
3. Detrmination of aminoacid sequence
Determnation of amino acid composition: The protein or polypeptide is completely hydrolyzed
to liberate the aminoacids which are quantitatively estimated. The hydrolysis may be carried
out either by acid or alkali treatment or by enzyme hydrolysis.
Degradation of protein into smaller fragments: Protein is a large molecule which is composed
of individual polypeptide chains. Separation of polypeptide is essential before degradation.
a.) Liberation of polypeptides: Treatment with urea or guanidine hydrochloride disrupts the
non-covalent bonds and dissociates the protein into polypeptide units. For cleaving the
disulphide linkages between the polypeptide units, treatment with performic acid is
24. b) Number of polypeptides: The no. of polypeptide chains can be identified by treatment of
protein with dansyl chloride.
It specifically binds with N-terminal aminoacids to form dansyl polypeptide which on hydrolysis
yield N-terminal dansyl aminoacid.
The no. of dansyl aminoacids produced is equal to the number of polypeptide chain in a protein.
c) Breakdown of polypeptides into fragments: Polypeptides are degraded into smaller peptide
by enzymatic or chemical methods.
Enzymatic cleavage: The proteolytic enzymes such as trypsin, chymotrypsin, pepsin and elastase
exhibit specificity in cleaving the peptide bonds.
Chemical cleavage: Cyanogen bromide is commonly used to split polypeptide into smaller
fragments. CNBr specifically splits peptide bonds, the carbonyl side of which is contributed by
the aminoacid methionine.
3. Determination of aminoacid sequence: Sanger used 1-fluro-2,4-dinitrobenzene to determine
insulin structure. FDNB specifically binds with N-terminal amino-acid to form a dinitrophenyl
derivative of peptide. DNP-aminoacid can be identified by chromatography.
25. Edmann’s reagent: Phenyl isothiocyanate is the Edman’s reagent. It reacts with the N-terminal
aminoacid of peptide to form a phenyl thiocarbamyl derivative. On treatment with mild acid, a
cyclic compound is liberated. This can be identified by chromatography.
Secondary structure: The confirmation of polypeptide chain by twisting or folding is referred to
as secondary structure.
Αlpha-Helix : It is most common spiral structure of protein. It has a rigid arrangement of
polypeptide chain. Alpha helical structure was proposed by Pauling and Corey.
The salient features of alpha helix
1. The alpha helix is tightly packed coiled structure with aminoacid side chains extending
outwards from the central axis.
2. The alpha-helix is stablized by extensive hydrogen bonding. It is formed between H atom
attached to peptide N, and O atom attached to peptide C.
3. Each turn of alpha helix contain 3.6aminoacids and travels a distance of 0.54nm. The spacing
of each aminoacid is 0.15nm.
26. 4. Stable conformation
5. Right handed alpha helix
Βeta-Pleated sheet: This is the second type of structure proposed by Pauling and
Corey. It is composed of two or more segments of fully extended peptide chains.
Tertiary structure: The three dimensional arrangemant of protein structure is reffered to as
tertiary structure. It is compact structure with hydrophobic side chains held interior while the
hydrophilic groups on the surface of the protein molecule.
Disulphide bonds (S-S), ionic interaction, hydrophobic interaction and vander waals forces also
contribute to the tertiary structure of proteins.
Aminoacids are a group of organic compound containing two functional groups like carboxyl
Zwitter ion, in the solution of Ph-7.4 worked as dipolar ion. In the dipolar form amino acids get
ionized in to amide and carboxylate ion.
The study of the transformation of energy in living organism.
Concept of free energy: It is defined as amount of energy available during the chemical
reaction to do the cellular work.
Endergonic and Exergonic reaction
Relationship between free energy, enthalpy and entropy
Free energy is also known as Gibbs energy. As per Gibbs free energy , driving force of chemical
is of two components viz. driving to words stability and drives towards disorder and is identified
in Gibbs equation. ΔG= ΔH-TDS
29. Enthalpy- It is total heat content of a sytem.
H= E +PV Ered = E˚red – RT/nf ln Q
Entropy – It is defined as measure of disorder or
uncertainity in a system. Δs = AQ/t
Redox potential: It is also known as oxidation and
reduction potential. It is important biochemical
reaction which is used to characterize the free
energy cost and direction of reaction involving
electron transfer. Redox potential is represented
by Nernst equation.
Energy rich compound: Biochemical compounds
releasing free energy during hydrolysis can be
classified into two classes.
i. High energy compounds
ii. Low energy compounds
iii. Molecule containing high energy bonds are
compounds are the cells currency. They can
be used to power energy consuming
biochemical reaction. If the energy of
hydrolysis of compound is more than 7.3K
cal/mol, it is referred hydrolysis of compound
is less than 7.3 kcal/mol, then it is low energy
Biological significance of ATP: Adenosine
triphosphate molecule is the nucleotide
known in biochemistry as the molecular
currency of intracellular energy transfer,
that is ATP is able to store and transport
chemical energy within cells. ATP also plays
an important role in the synthesis of
nucleic acids. ATP can be hydrolysed to
ADP, which can
ATP + H2O ADP + Pi + 7.3 k cal/mol
ADP + H2O AMP + Pi +
30. BIOLOGICAL SIGNIFICANCE OF cAMP
Cyclic adenosine monophosphate (cAMP) is a second messenger that is important in many
cAMP is derived from ATP and used for intracellular signal transduction in many different
organisms, transmission the cAMP dependent pathway.
In humans, cyclic AMP works by activating cAMP-dependent protein kinase. regulatory units of
the protein kinase and causes dissociation between the regulatory and catalytic subunits Thus it
activates the catalytic units and enables them to phosphorylate substrate proteins.
It regulate T cell function.
It also enhances the release of insulin.