Carbohydrates are polyhydroxyalcohols that contain an aldehyde or ketone group. They include monosaccharides like glucose and fructose, disaccharides like sucrose, and polysaccharides like starch and cellulose. Monosaccharides are classified based on number of carbons and functional groups, and many contain asymmetric carbons leading to isomers. Glycosaminoglycans are heteropolysaccharides made of repeating disaccharide units that provide structure and hydration to tissues. Carbohydrates serve important roles as energy stores, structural components, and in processes like blood clotting.

1. Chemical Nature of Carbohydrates
polyhydroxyalcohols with an aldehyde or keto group.
They are represented with general formulae
Cn(H2O)n and hence called hydrates of carbons
L - glyceraldehye

2. importance
dietary calories storage form of
energy in the body
cell membrane components
that mediate some forms of
intercellular communication

3. Classification of
Carbohydrates
Monosaccharides:
contain one
monosaccharide
unit
Polysaccharides:
contain more
than 10
monosaccharide
Disaccharides:
contain 2
monosaccharide
Oligosaccharides
contain 3 -10
monosaccharide

4. MONOSACCHARIDES
the general formula
(CH2O)n
classified
according to:-
The number of carbons in
the molecule into trioses (3
carbons), tetroses (4
carbons), pentoses (5
carbons), hexoses (6 carbons)
and heptoses (7 carbons)
The presence of
aldehyde or ketone
group into aldoses and
ketoses

5. Aldoses
Aldotrioses( C3) e.g.D-
glyceraldehyde
Aldopentoses (C5) e.g.
D-ribose and D-xylose.
glceraldehyde is the
mather of all aldoses
Aldotetroses (C4)
e.g. D-erythrose
Most of the
naturally
occurring
monosaccharid
es are of the D
type
Aldohexoses (C6) e.g. D-
glucose, D-mannose and
D-galactose

6. Ketoses
Ketotrioses (C3):
dihydroxyacetone
Ketopentoses (C5) e.g.
D-ribulose
dihydroxyacetoneis the
mather of all ketoses
Ketotetroses (C4)
e.g. D-erythrulose
D-Sedoheptulose
is the only one in
human that
contains seven
carbons; it is
formed in the
body from
glucose
Ketohexoses (C6) e.g. D-
fructose

7. Asymmetric (chiral)
carbon atoms
Carbon atom that attached
to 4 different atoms or
groups
Isomers are compounds
which have the same
molecular formula (the
same number and types of
atoms) but have different
structural formula
All monosaccharides
contain asymmetric carbon
atom(s) except dihydroxy
acetone
responsible for the
isomerism and the
optical activity
The number of isomers = 2n
( n = number of asymmetric
carbon atoms)
Glucose has 4 asymmetric
carbon atoms so has 16
isomers

8. Isomerism
Optical isomerism
dextrorotatory
(d or+ve) sugar
rotate PPL to
the right
levorotatory
(l or –ve)
sgere rotate
PPL to the
left
Stereo isomerism
Enantiomers: They are
the D- and L- forms of
the same compounds
(mirror images) eg. D
and L-glucose
Aldose-Ketose
Isomers
(Functional Group
Isomerism

9. Stereo isomerism
Epimers
compounds which
have more than
one asymmetric
carbon and differ
only in the
configuration
around one
carbon
Furanose and
pyranose forms
In solution, aldehyde
group of glucose
combines with hydroxyl
group of 5th carbon atom
forming 6 membered
heterocyclic pyranose
ring. And 5 membered
furanose ring structure is
formed from fructose
when its keto group
combines with hydroxyl
group on 5th carbon atom
Anomers
α and β
It refer to the orientation of
the OH group of anomeric
carbon atoms ring structure.
If it to the right………. α- sugar
If to the left ………… β-sugar

10. Important
Monosaccharides
Trioses and tetroses:
• Glyceraldehyde 3-phosphate
and dihydroxyacetonephosphate
are intermediates during glucose
oxidation in living cells.
Hexoses :
D-glucose (blood sugar)enters in the
formation of many disaccharides and
polysaccharides.
D-fructose (fruit sgar) component of sucrose
and inulin.
D-galactose component of lactose (milk sugar). It is
also found in glycosaminoglycans (GAGS),
glycolipids and glycoproteins
Pentoses :
D-ribose in RNA.
deoxyribose in
DNA.

11. Monosacchari
des
derivatives
Sugar acids:
Uronic acids :
The primary alcohol group of
monosaccharides is oxidised to
form the corresponding uronic
acid.
- Glucose is oxidised to form
glucuronic acid (GlcUA).
Aminosugars
glucosamine (GluN), galactosamine (GlaN)
and mannosamine (ManN)
-constituents of glycosaminoglycans (GAGs)
and some types of glycolipids and
glycoproteins.
-Several antibiotics contain aminosugars
which are important for their activity
Sugar alcohols
Glucose …………. Sorbitol
Manose…………....Mannitol
Galactose………….Galactitol
Fructose……..produces 2
alcohols (sorbitol and mannitol
Ribose…….ribitol (componat of
riboflavin B2)
Deoxy Sugers
as
deoxy ribose: It is
present in the
structure of DNA.
Reduction
oxidation
Oxygen removal Sugars with NH2
replaces the OH at C2

12. Monosaccharides
derivatives
Easter formation
a- Phosphate esters: as glucose 1-P and glucose 6-P.
b- Sulfate esters : They are present in certain types of
polysaccharides and glycolipids
(sulfolipids) e.g. β-D-galactose 3-sulfate
Another sugar (Glycon): e.g. formation of disaccharides and polysaccharides.
Non-Carbohydrate compound (Aglycon): such as alcohols, phenols or nitrogenous
bases.
-The glycosidic linkage is named according to the anomeric carbon to which it is
attached
(α & β) and according to the parent sugar e.g. glucosidic, galactosidic or
fructosidic bond.
- Examples of Glycosides:
-Nucleosides are glycosides formed of ribose or deoxyribose and a nitrogenous
base found in nucleic acids
OH of sugar +Acid
condensation of the anomeric
carbon of the sugar with

13. DISACCHARIDES
Reducing
have a free anomeric carbon in the second
sugar unit, so they exist in both α and β forms
Maltose (Malt
sugar)
*main product of
digestion of starch
by amylase
*composed of 2 D-
glucopyranose
connected by α -
(1,4) glycosidic
*hydrolyzed into 2
D glucos by Maltase
enzyme or acids
Non–Reducing
the 2 anomeric carbon of 2 sugers are
involved in the glycosidic link so not have free
anomeric carbon
Sucrose (Cane
sugar) (Table
sugar)
*It is formed of β-
D-fructofuranose
and α -D-
glucopyranose.
It is united by α 1,
2-glucosidic linkage
or β2,1-fructosidic
linkage
*Knowen as
inverted suger
* By hydrolysis give
glucose + Fractose
Isomaltose
*hydrolysis
products of
starch and
glycogen by
amylase, as it
represents the
branching point
of the molecule
*composed of 2
D-glucopyranose
connected by -
(1,6) glycosidic
bond
Lactose ( Milk
sugar):
- It is formed of β-
D-galactopyranose
and D-
glucopyranose
united by β1,4-
galactosidic
linkage.
-It is hydrolyzed by
lactase enzyme or
by acids into D-
glucose and D-
galactose

14. Polysaccharides
All nonreducing
Homopolysaccharides
formed from one type of
monosuccharids
Glucans:
formed of D-
glucose units
and include
starch, dextrins,
glycogen and
cellulose
heteropolysaccharides
formed from more than one type of
monosuccharids
Proteoglycans
*Formed of
GAGs+ Protein
core
They are formed
mainly of
carbohydrates
(95%) and only
(5%) proteins
Fructans:
formed of D-
fructose units
e.g. inulin
present in
plants
glycosaminoglycans
(GAGs) formly
called
mucopolysaccharid
es.
are:
Unbranched
-Long chains (usually >50
sugar units)
Composed of repeating
disaccharide units, usually
made up of an amino
sugar and a uronic acid.

15. Homopolysaccharides
Dextrins:
-They are produced
during the hydrolysis
of starch by salivary or
pancreatic amylase.
Cellulose
*In cell wall of plants.
*formed of long non-branched chain of β-D-
glucopyranose units connected together by β1,4-
glucosidic linkage.
* insoluble in water. It is non-hydrolysable by
amylase because it contains a β1,4-glucosidic
linkage.
-The presence of cellulose in diet is important as
it increases the bulk of food, which stimulates
intestinal contractions and prevents constipation
Starch :
*storage form of carbohydrates in
plants.
*present in large amounts in cereals
(rice and wheat), tubers (potatoes and
sweet potatoes) and legumes.
-*Starch granules contain two forms,
amylose (15- 20%) in the inner part
and amylopectin (80-85%) in the outer
part.
Glycogen:
is the storage form of
carbohydrates in animals
(animal starch).
-It is mainly present in
skeletal muscles and
liver.

16. Classification of Glycosaminoglycans
1- Sulfate free glycosaminoglycans: e.g. hyaluronic
Acid.
2- Sulfate containing glycosaminoglycans: e.g.
chondroitin sulphate, keratan sulphate, dermatan
sulphate, heparin and heparan sulphate

17. Functions of GAGs and proteoglycans
1-They are important constituents of extracellular matrix, the proteoglycans
interact with a variety of proteins in the matrix, such as collagen and elastin, and
theses interactions are important in determining the structural organization of the
matrix.
2-They are highly polar and attract water molecules, thereby creating a hydrated
gel. This gel:
A- Provides flexible mechanical support for the ECM.
B-Is compressible: when a GAG solution is compressed, water is squeezed out
and GAGs occupy a smaller volume. When the compression is released, their
molecules regain their original hydrated size. This gives GAGs solutions the
shock absorbing properties and explains their role as shock absorbents in
joints and making the eyeball resilient.
3- Hyaluronic acid proteoglycans is essential for wound repair. It allows rapid
migration of the cells to the site of connective tissue development.

18. 4-Heparin proteoglycan: is produced by mast cells present in the arteries, liver,
lung and skin.
Heparin function
1- anticoagulant i.e. prevents thrombus formation. It activates antithrombin &
inactivates coagulation factors IX, XI.
2- Release lipoprotein lipase from the capillary wall to blood, this enzyme helps
in removal and clearance of blood lipids (so lipoprotein lipase is known as
clearing factor).
5-Keratan sulfate proteoglycan is important for transparency of the cornea.
6-Heparan sulfate proteoglycans are associated mainly with plasma
membrane of cells and play an important role in cell membrane receptors and
cell-cell interactions.
7- Aggrecan: the major proteoglycan present in cartilage contributes to its
compressibility. It has a very complex structure containing many types of GAGs
(hyaluronic, chondroitin sulfate and keratan sulfate).
GAGs and aging:
Structure of aggrecan changes with age:
These changes may contribute to the development of osteoarthritis

19. Glycoproteins:
• They are proteins to which oligosaccharide chains are
covalently bound.
• They are found in mucous fluids, tissues, blood and
in cell membrane