1) Carbohydrates are an essential class of biomolecules that serve as the primary energy source for many organisms. They are classified into monosaccharides, oligosaccharides, and polysaccharides depending on their size. 2) Monosaccharides include glucose, fructose, and galactose. Oligosaccharides consist of 2-9 monosaccharide units and include disaccharides like sucrose and maltose. Polysaccharides are long chains of monosaccharide units and include starch, cellulose, and glycogen. 3) Carbohydrates play important biological roles like energy storage, structure, transport, and prevention of diseases. Glucose is a key energy source, while

1. UNIT-1 BIOMOLECULES
INTRODUCTION, CLASSIFICATION, CHEMICAL NATURE
AND BIOLOGICAL ROLE OF CARBOHYDRATE.
Presented by : Shubhrat Maheshwari

2. INTRODUCTION OF BIOMOLECULES
• Biomolecules are molecules that occur naturally in living organisms.
• Basic unit of the living system is a cell.
Cell various molecules (performs various functions of the cells)
Organic Inorganic
(C, H, O, N, P, S)
-Carbohydrates Water
-Lipids
-Proteins
-Amino acids
-Nucleic Acids
-Enzymes, etc.
Minerals and vitamins
✓ Essential minerals for plants- N, P, K, Ca, Mg, Fe, S, Cl, Mn, Zn, Cu ,
B, Mo and Ni.
✓ Essential minerals and vitamins for the animals-
▪ Minerals- Ca, Mg, P, Fe, I, K, Cu, Cr, Se, Mn & Zn.
▪ Vitamins- A, B1, B2, B3, B5, B6, B9, B12, C, D, E and K.

3. Definition of Biomolecules
• Biomolecules are certain molecules which are involved in maintenance &
metabolic process of living organisms/ cells.
• Biomolecules consists mainly of carbon and hydrogen with nitrogen, oxygen,
sulphur, and phosphorus. Biomolecules are very large molecules of many atoms,
which are covalently bound together.
• Elementary composition of the biomolecules are :-
Carbon(C)- 50%, Oxygen(O)- 20%,
Hydrogen(H)- 10%, Nitrogen(N)- 8.5%,
Phosphorus(P)- 2.5%, Sulphur(S)- 0.8%,
• These six elements together constitutes about more than 90% dry weight of
human body.

4. Characteristics of Biomolecules
• Most of biomolecules are organic in nature.
• They have characteristics sizes and three dimensional(3-D) structure.
• Functional groups present in the biomolecule is responsible for the
chemical properties.
• Structure of biomolecules are generally asymmetrical.
• Initially biomolecules will grow due to the chemical reactions.

5. CLASSIFICATION OF BIOMOLECULES
• Biomolecules classified on the basis of following concept:-
❖Filtrate contains Micromolecules.
❖Residue on filter paper contains Macromolecules.

6. Biomolecules
Micro molecules
Small sized, low mol. wt.
Less than 1000 Dalton sized
Examples-
Organic- amino acids, mono & di-
saccharides, enzymes.
Inorganic- water, minerals,
vitamins
Macromolecules
Large sized, high mol. wt.
More than 10000 Daltons sized
Examples
Proteins, nucleic acid (DNA &
RNA), polysaccharides, lipids.

7. CARBOHYDRATES
• Carbohydrate is an organic compound, it comprises of only oxygen, carbon and
hydrogen. Carbohydrates are good source of energy.
• The empirical formula being Cn(H2O)n ; where n ≤ 3.
• Ratio of C:H:O will be mostly 1:2:1.
• Definitions-Carbohydrates are hydrates of carbons. Carbohydrates are
polyhydroxy aldehydes or polyhydroxy ketones or which produce them on
hydrolysis.
• Carbohydrates are also known as saccharides, the word saccharide comes from
Greek word sakkron which means sugar.

8. CLASSIFICATION OF CARBOHYDRATES
• The carbohydrates are divided into three major classes depending upon whether
or not they undergo hydrolysis and if they do, on the number of products formed.
1. Monosaccharides
2. Oligosaccharides
3. Polysaccharides

10. 1. Monosaccharides
• Monosaccharides are sweet, crystalline and water soluble substances.
• The monosaccharides are polyhydroxy aldehydes or polyhydroxy ketones which
cannot be decomposed by hydrolysis to give simpler carbohydrates. e.g. Glucose,
fructose, Galactose etc.
• Monosaccharides categorized into two types according to the functional groups
present-
i. Aldoses :- Aldehyde group ( )
ii. Ketoses :- Ketone group ( )

11. • As per the number of carbon atoms monosaccharides are classified
into five types-
S. No. Types Aldoses Ketoses
1. Trioses (3C) Aldotriose
(Glyceraldehyde)
Ketotriose
(Dihydroxyacetone)
2. Tetroses (4C) Aldotetrose
(Erythose, Threose)
Ketotetrose
(Erythrulose)
3. Pentoses (5C) Aldopentose
(Ribose, Xylose, Arabinose)
Ketopentose
(Ribulose, Xylulose)
4. Hexoses (6C) Aldohexose
(Glucose, Galactose,
Mannose)
Ketohexose
(Fructose)
5. Heptoses (7C) Aldoheptose
(Glucoheptose)
Ketoheptose
(Sedoheptulose)

12. 2. Oligosaccharides
• The oligosaccharides (Oligo: few) are carbohydrates which yield a definite
number (2-9) of monosaccharide molecules on hydrolysis.
• Oligosaccharides are sweet, crystalline and water soluble substances.
• Only three types of oligosaccharides are natural occurring, which are:-
i. Disaccharides- Which yield two monosaccharides molecules on hydrolysis; e.g.
Sucrose, Maltose & lactose etc.

13. ii. Trisaccharides - Which yield three monosaccharides molecules on hydrolysis and
have molecular formula is C18H32O16. e.g.: Raffinose.
iii. Tetrasaccharides - Which yield four monosaccharides molecules on hydrolysis
and have molecular formula is C22H42O21.
e.g.: Stachyose[gal(α1→6)gal(α1→6)glu(α1↔2β)fru]

14. 3. Polysaccharide-
• The carbohydrates which have higher molecular weight, which yield many
monosaccharide molecules on hydrolysis.
• The polysaccharides on the other hand are amorphous, insoluble in water and
tasteless, they are called non-sugars.
E.g. Homo-polysaccharides:- Starch, Cellulose, Glycogen, Insulin etc.
Hetro-polysaccharides:- Gums, Agar, Pectin etc.

15. Different between Monosaccharaides, Oligosaccharides and
Polysaccharides
Character Monosaccharaides Oligosaccharides Polysaccharides
No. of sugar
molecules
1 2-9 More than 9
Glycoside bond Absent Present Present
Molecular
Weight
Low Moderate High
Taste Sweet Minimally sweet taste No taste
Solubility Soluble Soluble Insoluble
Nature Always reducing sugar May or may not be Always non reducing
sugar
Example Glucose, fructose, Galactose Sucrose, Maltose Starch, Glycogen, Dextrin,
Cellulose

16. Physical Properties of Carbohydrates
• Stereoisomerism - Compound shaving same structural formula but they differ in
spatial configuration. Example: Glucose has two isomers with respect to
penultimate carbon atom. They are D-glucose and L-glucose.
• Optical Activity - It is the rotation of plane polarized light forming (+) glucose and
(-) glucose.
• Distereo isomers - It the configurational changes with regard to C2, C3, or C4 in
glucose. Example: Mannose, galactose.
• Annomerism - It is the spatial configuration with respect to the first carbon atom
in aldoses and second carbon atom in ketoses.

17. Chemical nature and Structure of Carbohydrates
• There are three types of structural representations of
carbohydrates:
(i) Open chain structure.
(ii) Hemi-acetal structure.
(iii) Haworth structure

19. Open Chain Structure-
• Only one C-atom is double bonded with oxygen(O) atom.
• Carbonyl group present at the end of the chain is aldehyde and known as aldose.
• Carbonyl group present in any other position is Ketonic group and known as
ketose
• Due to presence of many hydroxyl, aldehyde and keto group these are known as
Polyhydroxy aldehyde or ketone.
D-Glucose D- Fructose

20. • D- and L- isomers
• D- and L- are relative configuration.
• D- and L- denotes about the arrangement of groups in horizontal line at asymmetrical carbon
atom.
Figure : D- and L- forms of glucose compared with D- and L- glyceraldehyde(the
reference carbohydrate)

21. • Sugars having same configuration as of D- glyceraldehyde at the most distant
asymmetrical carbon atom ( distance from carbonyl group) are considered as D- sugars or
carbohydrates.
• Sugar having opposite configuration ( or like L- glyceraldehyde) are considered as L-
sugars or carbohydrates.
Note-
Number of possible isomers :-
Number of possible optical isomers= 2n; where n= no. of asymmetrical carbon atoms in the molecule.
Aldotriose- 21 = 2 Ketotriose- 20 = 1
Aldotetrose- 22 = 4 Ketotetrose- 21 = 2
Aldopentose- 23 = 8 Ketopentose- 22 = 4
Aldohexose- 24 = 16 Ketohexose- 23 = 8
Aldoheptose- 25 = 32 Ketoheptose- 24 = 16

22. Mutarotation- The change in the specific optical rotation representing
the interconversion of α and β forms of D- glucose to the equilibrium
mixture.
Figure: Mutarotation of glucose representing α and β anomers (A) Fischer projection (B) Haworth Projection

23. • Glucose forms a stable Hemiacetal cyclic structure between –CHO and –OH
groups
C=O + CH3OH C
C
Aldehydic/Aldoses- Formation of hemiacetal group
Ketonic/ ketose- Formation of hemiketal group.
• Carbon containing carbonyl group will be Anomeric carbon after
hemiacetal formation.
O-
O+
H
CH3
OH
O-CH3
Carbonyl group

24. • α-D- glucose is less stable as compared to β- D- glucose.
• If we will dissolve α-D- glucose in water then some part will convert into β- D-
glucose and achieve the equilibrium I the solution and if we will take β- D-
glucose then reverse condition will occur.
Specific rotation
• α-D- glucose Equilibrium mixture β- D- glucose
+112.2ᵒ +52.4ᵒ +18.7ᵒ
• Due to more stability β- D- glucose will be present in higher percentage.

25. Biological role of Carbohydrates
• Carbohydrates are chief energy source, in many animals; they are instant source
of energy. Glucose is broken down by glycolysis/ kreb's cycle to yield ATP.
• Glucose is the source of storage of energy. It is stored as glycogen in animals and
starch in plants.
• Stored carbohydrates act as energy source instead of proteins.
• Carbohydrates are intermediates in biosynthesis of fats and proteins.
• Carbohydrates aid in regulation of nerve tissue and are the energy source for
brain.
• Carbohydrates get associated with lipids and proteins to form surface antigens,
receptor molecules, vitamins and antibiotics.

26. Biological role of Carbohydrates
• They form structural and protective components, like in cell wall of plants and
microorganisms.
• In animals they are important constituent of connective tissues.
• They participate in biological transport, cell-cell communication and activation of
growth factors.
• Carbohydrates those are rich in fibre content help to prevent constipation.
• Also they help in modulation of immune system.