Carbohydrates are the most abundant biological molecules and are composed of carbon, hydrogen, and oxygen. They serve important functions like energy storage, structure, and metabolism. Carbohydrates can be classified as monosaccharides, disaccharides, oligosaccharides, or polysaccharides depending on the number of monosaccharide units. Glucose is a widely abundant monosaccharide that forms cyclic structures and isomers. Disaccharides like sucrose, lactose, and maltose consist of two monosaccharide units. Polysaccharides are long chains of monosaccharides and include starch, glycogen, and cellulose, which serve structural and energy storage roles.

1. CARBOHYDRATES
Avinash Acharya

2. CARBOHYDRATES
INTRODUCTION
1.Mostly abundant in nature.
2.Composed of Carbon, Hydrogen & Oxygen.
3.Also known as hydrates of carbon.
4.Empirical formula (CH2O)n.
5.All carbohydrates can not be considered as
hydrates of carbon.
6.Definitions – On Hydrolysis of carbohydrates
they produce polyhydroxyaldehydes or
ketones or there compounds.

3. FUNCTIONS OF CARBOHYDRATES
1. Mostly abundant in nature.
2. Dietary source of energy.
3. 4 Cal/g for all organisms.
4. Participate in the structure of cell membrane and
cellular functions such as cell growth, adhesion and
fertilization.
5. Carbohydrates also serve as the storage form of energy
(glycogen) to meet the immediate energy demands of
the body.
6. Constituent of nucleotide that form RNA & DNA.
7. Carbohydrates are also involved in detoxification, e.g.
glucuronic acid.

4. CLASSIFICATIONS OF CARBOHYDRATES
Carbohydrates can be classified into 4 major groups
:-
1. Monosaccharides - (Mono= one &
saccharides = sugar)
2. Disaccharides - (Di= two & saccharides=
sugar)
3. Oligosaccharides - (Oligo= two to ten &
saccharides= sugar)
4. Polysaccharides - (Poly= more then 10 to
infinate & saccharides= sugar)

5. 1. MONOSACCHARIDES
• Simplest group of carbohydrates.
• Cannot be further hydrolysed.
• General formula = Cn(H2O)n.
• Monosaccharides are sweet in taste, crystalline, & soluble
in water.
• The most abundant monosaccharide in nature is six carbon
sugar-D-glucose.
A. The structure of glucose can be represented in three
ways:-
1. The straight chain structure formula (Fisher projection).
2. Cyclic formula (ring structure or Haworth projection).
3. Boat and chair form (x-ray diffraction analysis).

6. 1.The straight chain structure formula
(Fisher projection).

7. 2. Cyclic formula (ring structure or Haworth
projection)
• When the monosaccharides reactes with hydroxy (OH)
group of the same molecule in solution with aldehyde
group (CHO) to form hemiacetal and with ketone (C=O)
group to form hemiketal.

8. The Haworth projection formula for sugar
• The aldehyde group of glucose at C-1 reacts with alcohol (OH-) group
on carbon-5, represented by a symmetrical ring structure & depicted
by a Haworth Projection formula, in which glucose is considered as
having the same basic structure as pyran. A six member ring sugar
containing five carbon & one oxygen, is a derivative of pyran & is
called as pyranose.

9. • When linkage occurs with formation of five member ring
containing four carbons & one oxygen, the sugar has the
same basic structure as furan & is called furanose.

10. 3. Boat and chair form (x-ray diffraction analysis)
• X-ray diffraction analysis show that the six-membered ring containing
one oxygen atom is actually in the form of a boat or a chair.
• The chair is form is thermodynamically more stable then the boat
form.
• In solution the chair form predomintes.

11. B. Divided into 2 groups.
a. Based on functional group :-
Aldose - When the functional group in monosaccharides is an
Aldehyde (-C-H=O) e.g. Glyceraldehyde, glucose.
Ketose - When the functional group is keto (-C=O-) e.g.
Dihydroxyacetone, fructose.
b. Based on carbon atom :-
Monosaccharides can be divided into there carbon atoms.
(Table No. 1)
• Trioses (3C)
• Tetroses (4C)
• Pentoses (5C)
• Hexoses (6C)
• Heptoses (7C)
• Glucose is an aldohexose while Fructose is a ketohexoses.
• The common monosacharides & disaccharides of biological
importance are given in the Table No. 2 :-

12. TABLE No. 1. Classification of monosaccharides
with selected examples
Monosaccharides (empirical formula) Aldose Ketose
Trioses (C3H6O3) Glyceraldehyde Dihydroxyacetone
Tetroses (C4H8O4) Erythrose Erythrulose
Pentoses (C5H10O5) Ribose Ribulose
Pentoses (C6H12O6) Glucose Fructose
Heptoses (C6H12O6) Glucoheptose Sedoheptulose

13. Table No. 2 Monosaccharides of biological importance
Monosaccharides Occurrence Biochemical importance
1. Trioses -
Glyceraldehyde Found in cells as phosphate Glyceraldehyde 3-phosphate is an intermediate
in glycolysis
2. Tetroses -
D-Erythrose Widespread Its 4-phosphate is an intermediate in
carbohydrate metabolism
3. Pentoses -
D-Ribose Widespread as a constituent of RNA
and nucleotides
For the structure of RNA and nucleotide
coenzymes (ATP, NAD+, NADP+)
4. Hexoses -
D-Glucose As a constituent of polysaccharides
and diasaccharides. Also found in
fruits.
The ‘sugar fuel’ of life; excreted in urine in
diabetes. Structural unit of cellulose in plants
5. Heptoses -
D-Sedoheptulose Found in plants Its 7-phosphate is an intermediate in hexose
monophosphate shunt, and in photosynthesis

14. STRUCTURE OF GLUCOSE
• For the better undertanding of glucose , let us
consider for the structure of the hemiacetal and
hemiketels, respectively produced when the
aldehyde or ketone reactes with alcohol.

15. PYRANOSE AND FURANOSE STRUCTURE
• Haworth projection formulae are depicted by a six
membered ring pyranose (based on pyran) or a five-
membered ring furanose (based onfuran). The cyclic forms
of glucose are known as ɑ–D-glucopyranose and ɑ–D-
glucofuranose.

16. ISOMERISM
• Iso= equal; Meros= parts.
• The compounds possessing identical molecular formula but
different structure are referred to as isomers. The
phenomenon of existence of isomers is called isomerism.
• Various types of isomerism exhibited by sugar are:-
1. Structural isomerism
• Structural isomers have the same molecular formulae but
differ from each other by having different structure. For
example:-
• Aldose-ketose isomerism-
Glucose & fructose are isomers of each other having the same
chemical formula C6H12O6, but they are differ in structural
formula with respect to their functional groups.

17. 2. Stereoisomerism (due to the presence of symmetric carbon
atom)
• Stereoisomerism has same molecular formula & unlike structural
isomerism same structure but they differ in configuration, that is
the arrangement of their atoms in space.
• The presence of asymmetric carbon atoms allows the formations
of stereoisomerism.
• Glucose with four asymmetric carbon atoms can form 24 i.e. 16
isomers.

18. D & L ISOMERISM
• D & L isomers depends on the configuration of the asymmetric carbon
farthest form the carbonyl group.
• D & L isomers are mirror images of each other.
• Thus D & L isomerism depends on the orientation of the H & OH groups
around the asymmetric carbon atom adjacent to the terminal primary
alcohol carbon.
• When OH group on this carbon atom is on the right, it belonges to D-series,
when it is on left side it is the member of the L-series.
• Most of the monosaccharides in the living beinges belong to the D-series,
except L-fucose.

19. OPTICAL ISOMERISM
• Optical activity is the capacity of a substance to
rotate the plane polarized light passing through it.
• One member of the enantiomeric pair will rotate
the plane of the polarized light is a clockwise
direction & is therefore said to be dextrorotory
(d) or (+).
• its mirror image isomer or enantiomer will rotate
the plane of polarized light to be same extent, but
in the opposite or anticlockwise direction. This
isomer is said to be levorotatory (l) or (-).

20. MUTAROTATION
• Mutarotation is defined as a change in a specific
optical rotation representing the interconversion of
alpha & beta form of D-glucose equilibrium mixture.

21. DERIVATIVE OF MONOSACCHARIDES
1. Amino sugar- Amino sugar have a hydroxyl group replaced by an
amino or acetylated amino group. For example,
glucosamine, N-acetyl glucosamine, galactosamine & mannosamine.
Importance of amino sugar
• Amino sugars are components of glycolipid, glycoprotein,
proteoglycans.
• Several antibiotics, e.g. erthromycin, carbomycin contain amino
sugar.

22. 2. Sugar alcohol - They are not metabolically very active, but
have some medical importance in that they are used as non-
glucose forming sweetners in food stuffs for diabetics,
sorbitol & xylitol are the mostly commonly used.
3. Deoxy sugars – Deoxy sugars possess a hydrogen atom in
place of one of their hydroxy group. Example :-
• 2-deoxy ribose found in nucleic acid DNA,
• L-funose (6-deoxy-β-L-galactose) found in glycoprotein.

23. 4. Sugar acid – Sugar acid are produced by oxidation of the aldehydic
carbon, the hydroxyl carbon or both. For example:-
• Ascorbic acid or vitamin C. Ascorbic acid is required for the synthesis
of collagen. It acts as an water soluble antioxidant.
• Glucuronic acid.
5. Neuramic acid - Neuramic acid is a nine carbon sugar derived from
mannosamine & pyruvate.
Mannosamine + pyruvate Neuraminic acid
6. Sialic acid – Sialic acid are acetylated derivatives of neuraminic acid in
which amino (NH2) or hydroxy group is acetylated.

24. 2. DISACCHARIDES
Disacchari-
des
Structure Occurrence Biochemical
importance
1. Glucose As a constituent of
cane sugar and
beet sugar,
pineapple.
Most commonly used
table sugar supplying
calories.
2. Lactose Milk sugar. Exclusive
carbohydrate source
to breast fed
infants. Lactase
deficiency (lactose
intolerance)
leads to diarrhea and
flatulence.
3. Maltose Product of starch
hydrolysis, occurs
in germinating
seeds.
An important
intermediate in the
digestion of
occurs in germinating
seeds starch.

25. • A disaccharides consists of two monosaccharides unites
held with glycosides bond.
• They are crystalline, water-soluble and sweet to taste.
• There are two types of disaccharides :-
1. Reducing disaccharides - With free aldehyde or keto group.
E.g. maltose, lactose.
2. Non-reducing disaccharides – With free aldehyde or keto
group. E.g. sucrose, trehalose.
• Maltose is composed of two ɑ-D-glucose units held with
glycosidic bond.
• The osazone formation (shape) of maltose is sunflower
shaped.
1. MALTOSE

26. S.
No.
Type of
disaccharides
Osazone formation
shape
Structure
1.
Glucose
(Needle
shape).
2.
Lactose
(Powder-puff
or tennis ball
shape).
3.
Maltose
(Sunflower
shape).

27. • Sucrose is also commonly used table sugar.
• Sucrose is made of sugar cane or sugar beets.
• It is made of ɑ-D-glucose and β-D-fructose .
• Held with glycosidic bond b/w C1 of ɑ-glucose and
C2 of β-fructose.
• Non reducing sugar and cannot be form osazones.
• Food industry used for sweetening agent as sucrose.
• Sucrose is dextrorotory (+66.5°) in nature, but when
it is hydrolyzed and becomes levororotory (-28.2°).
• The hydrolyzed mixture of sucrose , containing
glucose & fructose, is known as invert sugar.
• When sucrose is hydrolyzed by enzyme sucrase, it
gives each molecule of glucose and fructose.

28. 3. LACTOSE
• Lactose is more commonly known as
milk sugar.
• Made up of β-D-galactose & β-D-
glucose.
• Lactose is most important
carbohydrate in the nutrition of
young mammales.
• It is hydrolysed by the enzyme lactase
into galactose & glucose.

29. 4. TREHALOSE
• Trehalose contain two glucose residues, joining by an glycosidic bond.
• The anomeric carbon of both monosaccharides units are involved in
the glycosidic bond.
• It is non-reducing sugar.
• It does not form osazone.
• Trehalose is a major sugar of insect hemolymph.
• Fungi & yeasts are the source of trehalose.

30. 3. OLIGOSACCHARIDES
• The diversity & complexity of the carbohydrate
oligosaccharide units of glycoprotein suggest that
they are rich in information & are functionally
important.
• Carbohydrates participates in molecular targeting
& cell – cell recognition.
• The oligosaccharides units actually mark the
passage of time & determines when the proteins
carrying them should be taken out of circulation.
• Proteins can be designed to have life times ranging
from a few hours to many weeks depending on the
physiological & biological needs.

31. CLASSIFICATION OF OLIGOSACCHARIDES WITH
EXAMPLES
Types of
oligosaccharides
No. of
monosaccharides
Examples Types of monosaccharides presents
Disaccharides Two Maltose Glucose + Glucose (C1-C4)
Lactose Glucose + Galactose
Sucrose Glucose + Fructose
Trehalose Glucose + Glucose (C1-C1)
Trisaccharides Three Raffinose Glucose + Galactose + Fructose
Tetrasaccharides Four Starchynose 2 molecules of Galactose + Glucose +
Fructose
Pentasaccharides Five Verbascose 3 molecules of Galactose + Glucose +
Fructose

32. 4. POLYSACCHARIDES
• Polysaccharides are also known as glycans or complex
carbohydrates, as well as they are branched polymers.
• Polysaccharides have high molecule weight & are only sparingly
soluble in cold water. They form colloidal solution when heated
with water.
• Consist of repeating unit of monosaccharides.
• They are very important in functions-structural & storage of
energy.
• There are two types of polysaccharides :-
1. Homopolysaccharides
2. Heteropolysaccharides
• Heteropolysaccharides is divided into :-
a) Mucopolysaccharides.

33. 1. HOMOPOLYSACCHARIDES
• Homo= single type of; Poly= more then ten; Saccharides=
sugar.
• On hydrolysis only a single type of monosaccharides.
• Glucans are polymers of glucose whereas fructosans are
polymers of fructose.
• Types of homopolysaccharides :-
1. Starch-
• Mostly found in plants.
• Important dietary source for higher animals, including
humans.
• High storage in cereals, roots, tubers, vegetables etc.
• Composed of D-glucose unite held with ɑ-glycosidic bonds.
• It is known as glucosan or glucan.

34. • Starch has two components :-
1. water soluble amylose (15-20%) &
2. Water in-soluble amylopectin (80-85%).
• Starch get hydrolysed by amylase (found in salivary &
pancreatic ) to liberate dextrins & finally into maltose &
glucose.

35. 2. Inulin
• Inulin is a polymer of fructose.
• Found in garlic & onion .
• Low molecular weight around 5000 & easy water soluble
in water.
• Not utilized in the body.
• But it is used for measuring the glomerular filtration rate
(GFR) for kidney functional.

36. 3. Glycogen
• Glycogen is the carbohydrate reserve in humans & animals hence
referred to as animal starch.
• Present in high concentration in liver .
• Glycogen also found in those plants who does not have chlorophyll
such as yeast, fungi.

37. 4. Cellulose
• Abundantly found in plant kingdom.
• Composed of repeating unit β-D-glucose.
• Cannot be digested by humans due to lack of the enzyme that cleaves
β-glycosidic bond.
• Cellulose cannot be digested but it has important in human nutrition
as a fiber.
• B’coz it decreases the absorption of glucose and cholesterol from
intestine which incerases the bulk of feces.

38. 2. HETEROPOLYSACCHARIDES
• When polysaccharides is composed of different types of sugars or
there derivative.
• Homopolysaccharides is also refered as heteroglycans.
• Type of heteropolysacchaeides :-
a) MUCOPOLYSACCHARIDES
• Amino sugars & Uronic acids are made up of mucopolysaccharides.
• Mucopolysaccharides can also be known as glycoaminoglycans
(GAG) .

39. • Some of the mucopolysaccharies are found in combination with proteins to form
mucoproteins or mucoides or proteoglycans.
• Mucoprotiens may contain up to 95% carbohydrates & 5% protein.
• They are essential for components of tissue structure.
Occurrence of GAG’s :-
• Proteoglycans are found in the-
1. Synovial fluid of joints.
2. Vitreous humour of the eye.
3. Arterial wall.
4. Bone &
5. Cartilage.
FUNCTIONS OF GAG’S
1. They are the major components of the extracellular matric or ground substance.
2. They also give resilience (elasticity) to the substance such as cartilages,
permitting compressed & re-expansion.
3. This property contributes to the resilience of synovial fluid & vitreous humour of
the eye.
4. They lubricate joints both at the surface of cartilage & synovial fluid.
5. The viscous lubricating properties of mucous secretions are also due to the
presence of glycosaminoglycans, which led to the original naming of there
compounds as mucopolysaccharides.

40. • Types of mucopolysaccharides:-
1. HYALURONIC ACID
• Important glycoaminoglycans (GAG) found in synovial fluid
of joints & vitreous humor of eyes.
• Also found in a form of a gel around the ovum.
• Hyaluronic acid serves as a lubricant & shock absorbant in
joints.

41. • Composed of D-glucoronic acid & N-acetyl D-glucosamine.
• Hyaluronidase is an enzyme break hyaluronic acid & other GAG.
• This enzyme is highly present in testes, seminal fluid & in certain
snakes & insect venoms.
• Hyaluronidase os semen is assigend an important role in fertilization
as this enzyme clears the gel around the ovum.
2. CHONDROITIN SULFATES
• Chondroitin 4-sulfate is a major constituent of various mammalian
tissue.
• It is made up of D-glucuronic acid & N-acetyl D-galactosamine

42. 3. HEPARIN
• Heparin is an anticoagulant that occure in blood, lungs, liver, kidney,
spleen etc.
• It helps in the release of the enzyme lipoprotein lipase which helps in
clearing the turbidity of lipemic plasma.
• Heparin is composed of N-sulfo D- glucosamine 6-sulfate &
glucuronate 2-sulfate.

43. 4. DERMATAN SULPHATE
• Mostly found in skin.
• Structure is mostly related to chondroitin 4-sulphate.
• The composition is made up of D-glucuronic acid & L-iduronic acid.
• The only difference around C5 of D-glucuronic acid to L-iduronic acid.

44. 5. KERATAN SULFATE
• It is a heterogeneous GAG with a variable sulfate content.
• Besides small amounts of mannose, fructose, sialic acid etc.
• It keeps cornea transparants.
• It is made up of D-galactosamine & N-acetylglucosamine 6-
sulfate.

45. TABLE NO.5

46. AGAR & PECTINS
• Agar is mostly found in sea weeds
• It is a polymer of galactose sulfate & glucose.
• Agar is not digested but it is serves as a dietary
fibers.
• Agarose is used in the lab. As a major component of
microbial culture media & in electrophoresis.
• Pectins are found in apples & citrus food, contain
galactouronate & rhamnose.
• Pectins is not digested but it is serves as a dietary
fibers.
• They are also employed in the preparation of jellies.

47. GLYCOPROTEINS
• Many proteins are covalently bound to carbohydrates which are
referred to as glycoproteins.
• Glycoproterins are very widely distributed in the cells & perform
variety of fuctions.
• Some of the major fuctions of glycoproteins are given the table no.6 :-

48. ANTIFREEZE GLYCOPROTEINS
• Antifreeze glycoprote in which lower the freezing point of
water and interfere with the crystal formation of ice.
• Antifreeze glycoproteins consist of 50 repeating units of the
tripeptide, alanine-alanine-threonine.
• Each threonine residue is bound to β-galactosyl ɑ-N-
acetylgalactosamine.
BLOOD GROUP SUBSTANCES
• The blood group antigens (of erythrocyte membrane)
contain carbohydrates as glycoproteins or glycolipids.
• N-Acetylgalactosamine, galactose, fucose, sialic acid etc. are
found in the blood group substances.
• The carbohydrate content also plays a determinant role in
blood grouping.