The document provides an extensive overview of carbohydrates, including their chemical structures, classifications, properties, and biological functions. It discusses the roles of monosaccharides, disaccharides, and polysaccharides in energy storage, protein sparing, and cellular functions, while also detailing enzymatic digestion processes and various chemical reactions associated with carbohydrates. Additionally, it covers the historical nomenclature of carbohydrates and the significance of their structural variations.

1. CARBOHYDRATES
(INTRODUCTION
AND
Dr. V. MANON MANI
ASSISTANT PROFESSOR
IN
LIFE SCIENCES
KRISTU JAYANTI COLLEGE
BENGALURU- 560077

2. Robert Hooke

4. All cells are bounded by a plasma membrane; have
a cytosol containing metabolites, coenzymes,
inorganic ions, and enzymes; and have a set of
genes contained within a nucleoid (prokaryotes) or
nucleus (eukaryotes).
Phototrophs use sunlight to do work; chemotrophs
oxidize fuels, passing electrons to good electron
acceptors: inorganic compounds, organic
compounds, or molecular oxygen.

5. Bacterial
plasmids.
cells contain cytosol, a nucleoid, and
Eukaryotic cells have a nucleus and are multi-
compartmented, segregating certain processes in
specific organelles, which can be separated and studied
in isolation.
Cytoskeletal proteins assemble into long filaments that
give cells shape and rigidity and serve as rails along
which cellular organelles move throughout the cell.

6. Supramolecular complexes are held together
by non- covalent interactions and form a
hierarchy of structures, some visible with the
light microscope. When individual molecules
are removed from these complexes to be
studied in vitro, interactions important in the
living cell may be lost.

7. CARBOHYDRATES

8. German
chemist
Carl
Schmidt
(chemist) in
1844
Chemical structure:
German
biochemist Emil
Fischer
1884

9. 1838, Dumas coined the term ‘glucose’ (Greek gleukos or sweet wine)
1840, Anselme Payen coined the term cellulose from the French word ‘cellule’ for cell
1855, Claude Bernard isolated and coined the term ‘glycogen’ for the starch like substance stored in the livers of
mammals
1857, William Miller coined the term ‘sucrose’ for common table sugar extracted from sugarcane or beet
1858, Dumas- the molecular formula of Dumas’ glucose C6
H12
O6
was established
1866, Kekulé proposed the name dextrose for dextrorotatory glucose
Tentative Rules for Carbohydrate Nomenclature, Part I, 1969, published in 1971/72 was published by the
IUPAC-IUB Commission on Biochemical Nomenclature

10. CARBOHYDRATES
Carbohydrates - containing a group of naturally occurring
carbonyl compounds (aldehydes or ketones) - several
hydroxyl groups.
Carbon (C), hydrogen (H), and oxygen (O) atoms, -
hydrogen-oxygen atom ratio of 2:1 (as in water).
Empirical formula Cm(H2O)n
(where m and n may or may not be different) or
(CH2O)n
They are organic compounds organized in the form of
aldehydes or ketones with multiple hydroxyl groups coming
off the carbon chain.
The building blocks of all carbohydrates are simple sugars
called monosaccharides.
A monosaccharide can be a polyhydroxy aldehyde (aldose) or
a polyhydroxy ketone (ketose).

11. The carbohydrates can be structurally represented in any of the three
forms: Open chain structure.
Hemi-acetal structure.
Haworth structure.
Open chain
structure – It is the
long straight-chain
form of
carbohydrates.
Hemi-acetal structure – Here the 1st carbon of the glucose condenses with the -OH group of the
5th carbon to form a ring structure.
Haworth structure – It is the presence of the pyranose ring structure.

15. Chain
Position
Functional
Metamerism
•This type of isomerism arises due to the presence
of different alkyl chains on each side of the
functional group.
•It is a rare type of isomerism and is generally
limited to molecules that contain a divalent atom
(such as sulphur or oxygen), surrounded by alkyl
groups.
•Example: C4
H10
O can be represented
as ethoxyethane (C2
H5
OC2
H5
) and methoxy-
propane (CH3
OC3
H7
).

16. Tautomerism
•A tautomer of a compound refers to the isomer of the
compound which only differs in the position of
protons and electrons.
•Typically, the tautomers of a
compound together in equilibrium and easily
interchange.
•It occurs via an intramolecular proton transfer.
exist
•An important example of this phenomenon
is Keto-enol tautomerism.
Ring-Chain Isomerism
•In ring-chain isomerism, one of the isomers has
an open-chain structure whereas the other has a
ring structure.
•They generally contain a different number of pi
bonds.
•A great example of this type of isomerism can be
observed in C3
H6
. Propene and cyclopropane are
the resulting isomers

18. Geometric Isomerism
•It is popularly known as cis-trans isomerism.
Optical Isomerism
•Compounds that exhibit optical isomerism feature similar bonds
but different spatial arrangements of atoms forming non-
superimposable mirror images.
•These optical isomers are also known as enantiomers.
•Enantiomers differ from each other in their optical activities.

19. PROPERTIES
Energy Storage: When the body has excess energy, i
stores it as glycogen. Most of this glycogen is stored i
the muscles and liver. It acts as a readily available
energy reserve for times when glucose intake is
Physical Properties of Carbohydrates
•Stereoisomerism – Compound shaving the same structurinalsufficient.
formula but they differ in spatial configuration. Example:
Glucose has two isomers with - carbon atom. They
are D-glucose and L-glucose.
•Optical Activity – It is the rotation of plane-polarized light
forming (+) glucose and (-) glucose.
•Diastereo 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 the second carbon atom
in ketoses.

20. Energy Production:
The primary role of
carbohydrates is to supply
energy to all cells.
Glucose, - preferred energy
source for many cells. Red
blood cells and the brain, in
particular, rely exclusively on
glucose for energy
production.
respiration breaks
glucose,
from its
capturing
chemical
Cellular
down
energy
bonds.

21. Building Macromolecules: Carbohydrates contribute to the formation of larger molecules.
For instance, they play a role in constructing glycoproteins, which are essential for cell
communication and immune function.
Sparing Protein: Carbohydrates help spare protein by providing an alternative energy
source. When carbohydrates are available, the body uses them for energy, preserving
protein for other vital functions.
Assisting in Lipid Metabolism: Carbohydrates influence lipid metabolism by regulating
enzymes involved in fat breakdown and synthesis.

22. 1. Digestion
Carbohydrate digestion begins in the mouth and continues through the
body, ultimately providing essential energy for various
cellular
functions.
2. Absorption: Carbohydrate digestion begins in the mouth, where
salivary amylase acts on starches. The process continues in the
duodenum with pancreatic amylase. Monosaccharides (such as glucose)
are then absorbed across the epithelium of the small intestine and
transported to tissues via the circulatory system.
3. Metabolism: Glycolysis; Electron Transport Chain (ETC); Overall
ATP Production.

23. Chemical Properties of Carbohydrates
•Osazone formation: Osazone are carbohydrate derivatives when sugars are reacted
with an excess of phenylhydrazine. eg. Glucosazone
•Benedict’s test: Reducing sugars when heated in the presence of an alkali gets
converted to powerful reducing species known as enediols.
•When Benedict’s reagent solution and reducing sugars are heated together, the
solution changes its color to orange-red/ brick red.
•Oxidation: Monosaccharides are reducing sugars if their carbonyl groups oxidize to
give carboxylic acids. In Benedict’s test, D-glucose is oxidized to D-gluconic acid thus,
glucose is considered a reducing sugar.
•Reduction to alcohols: The C=O groups in open-chain forms of carbohydrates can be
reduced to alcohols by sodium borohydride, NaBH4
, or catalytic hydrogenation (H2,
Ni, EtOH/H2O). The products are known as “alditols”.

24. CLASSIFICATION
•Monosaccharide, disaccharide, oligosaccharide
and polysaccharide.
•Carbohydrates - either a straight chain or a ring
structure.
•Ring structure - incorporate two additional functional
groups the hemiacetal and acetal.

26. •Living organisms use carbohydrates as accessible energy to fuel cellular
reactions. They are the most abundant dietary source of energy (4kcal/gram) for
all living beings.
•Carbohydrates along with being the chief energy source, in many animals, are
instant sources of energy. Glucose is broken down by glycolysis/ Kreb’s
cycle to yield ATP.
•Serve as energy stores, fuels, and metabolic intermediates. It is stored as
glycogen in animals and starch in plants.
•Stored carbohydrates act as an energy source instead of proteins.
FUNCTIONS OF
CARBOHYDRATES

27. •They form structural and protective components, like in the cell wall of plants and
microorganisms. Structural elements in the cell walls of bacteria (peptidoglycan or murein),
plants (cellulose), and animals (chitin).
•Carbohydrates are intermediates in the biosynthesis of fats and proteins.
•Carbohydrates aid in the regulation of nerve tissue and is the energy source for the brain.
•Carbohydrates get associated with lipids and proteins to form surface antigens, receptor
molecules, vitamins, and antibiotics.
•Formation of the structural framework of RNA and DNA (ribonucleic acid and
deoxyribonucleic acid).
•They are linked to many proteins and lipids. Linked carbohydrates are important in cell-cell
communication and in interactions between cells and other elements in the cellular
environment.

28. •In animals, they are an important constituent of connective tissues.
•Carbohydrates that are rich in fiber content help to prevent
constipation.
•Also, they help in the modulation of the immune system.

29. 1. MONOSACCHARIDE :-
1.Monosaccharides - simplest carbohydrates.
2.Those carbohydrates- single polyhydroxy derivatives of
either aldehydes or ketones - Monosaccharides.
3.General formula (Cn
H2
O)n
.
4.Cannot be hydrolyzed .
5.Example - glucose,
fructose, galactose, xylose
and ribose.
6. Monosaccharides - simple
sugar.

30. The simple
carbohydrates –
single sugars
(monosaccharides)
and
Polymers-
oligosaccharides,
and polysaccharides.

31. 2. CHEMICAL CHARACTERISTICS OF MONOSACCHARIDE :-
1.One sugar - colourless, water soluble, crystalline solid.
2.Some monosaccharide - sweet taste.
3.The backbone - unbranched carbon chain - carbon atoms are linked
by single bonds.
to an
4.In open chain from one of the other carbons is double
bounded oxygen atom to from a carbonyl group.
5. Each of the other carbon atoms has a hydroxyl group.
6.Despite their high molecular weights, the presence of large numbers of OH
groups makes the monosaccharides much more water-soluble than most
molecules of similar MW.
7.Glucose can dissolve in minute amounts of water to make a syrup (1 g / 1
ml H2O).

32. 3.CLASSIFICATION OF MONOSACCHARIDE
On the basis of length of carbon chain
CARBON CATEGORY
NAME
EXAMPLE
3 TRIOSE GLYCERADEHYDE,DIHYDROX
YACETONE
4 TETROSE ERYTRROSE
5 PENTOSE RIBULOSE, RIBOSE, XYLOSE
6 HEXOSE GLUCOSE, GALACTOSE,
MANNOSE, FRUTOSE
7 HEXOSE SEDOHEPTULOSE

34. On the basis of nature of carbonyl group-
1. ALDOSES
2. KETOSES
Aldoses If the carbonyl group is at the end of the chain
the monosaccharide is an aldehyde derivative and called an aldose
Ketoses
If the carbonyl group is at any other position in the chain -
the monosaccharide is a ketone derivative and called a ketoses.

36. CARBON ATOM ALDOSES KETOSES
TRIOSE GLYCERALDEHYDE DIHYDROXY
ACETONE
TETROSE ERYTHROSE ERYTHRULOSE
PENTOSE RIBOSE, XYLOSE,
ARABINOSE
RIBULOSE,
XYLULOSE
HEXOSE GLUCOSE,
GALACTOSE,
MANNOSE
FRUCTOSE
HEPTOSE GLUCOPEPTOSE,
GALACTOHEPTOSE
SEDOPEPTULOSE

37. 4.
PROPERTIES
1.Stereoisomerism
I. Stereoisomerism - significant
character.
II. Stereo isomers - same
structural formula but differ in
their spatial configuration.

38. A) Asymmetric carbon atom
1.A carbon - asymmetric when it is attached to four
different atoms or groups.
2.The number of asymmetric carbon atoms (n)
determines the possible isomers of a given
compound which is equal to 2n
3.All monosaccharides except dihydroxyacetone -
one or more asymmetric carbon atom and thus are
chiral molecule.
4.Glucose - 4 asymmetric carbon and thus has 16
isomers.

39. B) D and L isomer
•The D and L isomer - mirror image
of each other .
•The spatial orientation of H and OH
groups on the carbon atom (C5
for
glucose) that is
terminal
primary
adjacent to
the
alcohol
carbon
determines whether the sugar is
D and L isomer.

40. • If the OH group is on the right side -
sugar is of D series.
• If on the left side, it belongs to L
series.
• The structures of D and L glucose based
on the reference monosaccharide.
(C) Optical activity of sugar
1.Optical activity is a characteristic feature
of compounds with asymmetric carbon
atom.
2.When a beam of polarised light is
passed through a solution of an optical
isomer ,it will be rotated either to right or
left.

41. 3. The term dextrorotatory (+) and levorotatory (-)
-rotate the plane of polarized light to the right or to
the left.
2.Mutarotation and Anomeric forms of Glucose
1.Isomeric forms of monosaccharides that differ
only their configuration about the hemiacetal or
hemiketal carbon atom are called anomers.
2.The α and β anomers of D-glucose interconvert
in aqueous solution by a process called
mutarotation.
3.A solution of α D-glucose and a solution of β D-
glucose eventually form identical optical properties.

43. 3.CYCLIC FORM OF MONOSACCHARIDES
•Monosaccharide - five or more carbon atoms in the backbone usually
occur in solution as cyclic or ring structure.
•In which the carbonyl group is not free as written but has formed a
covalent bond with one of the hydroxyl groups along the chain.

44. 3.The aldehydes and Ketones moieties - five and
six carbon will spontaneously react with alcohol
groups present in neighbouring carbons to
produce intramolecular hemiacetals or hemiketal,
respectively.
4.This result in the formation of five or six
membered rings - 5 membered ring structures
resemble the organic molecule furon, derivatives
with this structure are termed furanoses.
5.Those with six numbered rings resemble the
organic molecules pyron and are termed as
pyranoses.

46. 4. IMPORTANT CHEMICAL
REACTIONS OF
MONOSACCHARIDE
IODO COMPOUND
•An aldose sugar, when heated with
concentrated hydrodic acid (HI) loses all
of its oxygen and is converted into an iodo
compound (glucose to iodohexane,C6
H12
I)
ESTER FORMATION
•Sugar by virtue of the alcohol group,
readily form ESTER with acids.
•All the free OH groups are

47. ACETYLATION
•The acetylation with acetyl chloride indicates the presence of
present in the sugar.
•The presence of 5 OH group of glucose results in a penta
actate.
OH groups
OXIDATION
• Oxidation of the aldehyde group forms ‘aldonic acids’.
•If the aldehyde group remains intact and the primary alcohol group is oxidized
‘uronic acid’ are formed .

49. REDUCTION -
•The monosaccharides are reduced to their
corresponding alcohols by reducing agent such as
sodium amalgam.
Thus, glucose yield orbital.
-Galactose yield dulcitol.
-Mannose yield mannitol.
-Fructose yield mannitol sorbitol.

50. OSAZONE FORMATION
•It is nothing but the formation of crystalline derivatives of the sugars
which are valuable in the identification of sugars.
•These crystals are obtained by adding a mixture of phenyl hydrazine
hydrochloride and sodium acetate to the sugar solution and heating in a
boiling water bath.
•The carbonyl group and the next adjacent carbon are involved this
reaction .With an aldose the reaction is shown.
•The hydrazone then reacts with two additional molecules of
phenylhydrazine to from the osazons. The ketones also show similar
reaction.

51. OTHER REACTION
•The best known tests are reduction of
metallic hydroxides together with oxidation
of the sugar.
•The alkaline metal is kept in solution with
sodium potassium titrate (Fehling’s solution)
or sodium citrate (Benedict’s solution).
•Barford’s test distinguishes between
monosaccharides and disaccharides.
•The copper acetate in dilute acid is reduced
in 30 seconds by monosaccharides whereas
reduction of the same takes several minutes
by disaccharides.

52. Thank you…