Carbohydrate structure

1. Carbohydrates chemistry
Dr : Abdel

naser

Badawy

2. ‐

Carbohydrates  are organic molecules found in nature, 

constituting one of the four major classes  of biomolecules. 
‐ ‐

The other three are proteins, nucleic acids  and lipids.
- -
Saccharides

(saccharo

is Greek for ―sugar)

3. •

Carbohydrates are aldehyde

or
ketone

compounds with multiple
hydroxyl groups.
•

The basic molecular formula
(C.H
2

O)
n

where n = 3 or more.
•

The term ―carbohydrate comes
from the observation that when you
heat sugars, you get carbon and
water (hence, hydrate of carbon ).

4. Classification 
They are classified according to the number of structural units  into:
1‐Monosaccharides=

They  are the simplest carbohydrates that can not 

be hydrolysed

into simpler  units.
2‐

Disaccharides=

produce  2 molecules of monosaccharide on 

hydrolysis.
3‐

Oligosaccharides=

produce  three to ten monosaccharide units on 

hydrolysis
4‐

Polysaccharides=

: produce  more  than 10 monosaccharide units on 

hydrolysis

5. Monosaccarides -1
•

* Def :

They are the simplest
carbohydrate unites which can not be
hydrolyzed to a simpler form
•

* General formula:

(CH
2

O)
n

n≥3

6. : * Nomenclature
•

1-

According to active group in
the sugar:
–

If monosaccharide contains
aldehyde

group (CHO) →it's
called aldose.
–

And if contain ketone

group
(c=o) →it's called
ketose.

7. According to the number  of carbon atoms (n): ‐2
If sugar  contains 
3 carbons →it's called triose,  4c→tetrose

5c→pentose           

6c→hexose

7c→heptose

8. Three Carbon
Four Carbon
By combining the two methods , we find that: -33c-Aldotriose -ketotriose
4c-Aldotetrose -ketotetrose
5c-Aldopentise -ketopentose
6c-Aldohexose -ketohexose

9. Five Carbon
Six Carbon

10. The structure of glucose  can be represented in one of the 

following ways:
1.The  straight –chain (open  ‐

chain) structural formula :
Aldohexose

can account for some of the properties of glucose, but 

can not explain  some reaction   
D-glucose

11. 2. The cyclic structure

accounts for the remainder  of the chemical 

properties of glucose. This cyclic  structure can be represented in two 

forms:
a. Fischer  projection  formula  :
where the aldehyde

group reacts with 

an alcohol group on the same sugar to form  a hemiacetal

ring.
C
H –C –OH   
HO –C –H 
H –C –OH  
H –C 
CH
2
OH  
α‐D‐Glucopyranose
H    OH
O
C
H –C –OH   
HO –C –H 
H –C –OH  
H –C 
CH
2
OH  
β‐D‐Glucopyranose
o
HH
O

12. b. Haworth formula: Where the cyclic structure is represented in pyranose

(six –

membered) and

 
furanose

(five –

membered) rings resembling pyran

and furan  rings. 
Here  oH

and H written above  and below instead of Right and left 
so what is on  Right  →below                      left →above 
except last carbon  (which close the ring)  in which   
left  →below                                                       Right

→above
α‐D‐Glucopyranose

13. An aldehyde or ketone can react with an
alcohol in a 1:1 ratio to yield a hemiacetal or
hemiketal, respectively, creating a new chiral
center at the carbonyl carbon
Hemiacetals o r

Hemiketals

14. : c) Boat and chair  forms
represents the three dimensional configuration  of sugar in nature.

15. forms haworth Fructose in open  chain & 

16. carbon, Asymmetric Anomeric

carbon): chiral carbon atom (
•

It is that carbon atom attached
to four different groups or
atoms.
•

Formation of a ring results in the
creation of an anomeric

carbon
at carbon 1 of an aldose

or at
carbon 2 of a ketose.

17. Reducing sugars
•

If the oxygen on the anomeric
carbon (the carbonyl group) of a
sugar is not attached to any
other structure, that sugar is a
reducing sugar.
•

Only the state of the oxygen on
the anomeric

carbon determines
if the sugar is reducing or
nonreducing—the other hydroxyl
groups on the molecule are not
involved

18. Reducing sugars
•

A reducing sugar can
react with chemical
reagents (for
example, Benedict's
solution) and reduce
the reactive
component, with the
anomeric

carbon
becoming oxidized.

19. Any compound having  one or more asymmetric  carbon atom 

shows  two properties:
1.

Optical  activity.
2.

Stereoisomerism 

20. Optical activity -1
•

Def.

It is the ability of the compound to rotate
plane polarized light to the right or to the left.
•

If the compound rotates plane polarized light
to the right, it is called dextrorotatory, d or
(+).
•

If it rotates plane polarized light to the left, it
is called levorotatory, l or (-).

21. •

The direction of rotation is independent
of the stereochemistry
•

of the sugar, so it may be designated
D(−), D(+), L(−), or L(+).
•

For example, the naturally occurring
form of fructose is the D(−) isomer.

22. ••

dextrorotatory dextrorotatory sugar (d or +): sugar (d or +):
glucose, glucose, galactose galactose

and starch and starch
••

levorotatory levorotatory sugar (l or sugar (l or --): ): fructose fructose
and invert sugar and invert sugar..

23. 2‐

Stereoisomerism


Compound 

that 

have  

the 

same  

structural  

formula 

but 

differ  

in 

spatial 

configuration 

are 

known  

as 

stereoisomers

and 

the 

phenomenon is called stereoisomerism. 


The 

number 

of 

possible 

isomers 

of 

a 

compound 

depends 

on 

the 

number of asymmetric  carbon  atoms (n) and is equal to 2
n
. 


Glucose, with four asymmetric  carbon  atoms, has 16 isomers.  

24. •

The more important types of isomers
include
–

D and L isomers,
–

pyranose

and furanose

ring structures,
–

alpha and beta anomers,
–

epimers

and
–

aldose-ketose

isomers.

25. Isomers Isomers Are compounds which have the same molecular Are compounds which have the same molecular
weight, same percentage composition, and differ weight, same percentage composition, and differ
in their physical and chemical properties. in their physical and chemical properties.
--

Stereoisomers Stereoisomers: are compounds that have the : are compounds that have the
same structural formula but differ in spatial same structural formula but differ in spatial
configuration (arrangement of atoms and groups configuration (arrangement of atoms and groups
of atoms in space around the asymmetric of atoms in space around the asymmetric
carbon(s carbon(s) i.e. different configuration). ) i.e. different configuration).

26. 1. D and L isomers
): enantiomers (
•

A special type of
isomerism is found in
the pairs of structures
that are mirror image of
each other.
•

These mirror images
are called enantiomers
and the two members of
the pair are designated
as a D and an L-sugar.

27. •

A monosaccharide is
designated D if the
hydroxyl group on the
highest numbered
asymmetric carbon=
prelast

carbon

is drawn to
the right as in D-
glyceraldehyde

and L if the
hydroxyl group on the
highest numbered
asymmetric carbon is
drawn to the left as in L-
glyceraldehyde.

29. ‐

The  majority of the sugars in humans are D‐sugars.  
‐

Two exceptions  are L‐fucose

(in glycoproleins) and L‐iduronic

acid 
(in glycosaminoglycans).

30. ring structures:  furanose and  Pyranose 2. 
The   monosaccharides

are  either  pyran

(a six‐membered
ring) or furan (a five ‐membered

ring). 
For glucose in solution, more  than 99% is in the pyranose

form.

31. : anomers 3. Alpha and beta 
The ring structure of an aldose

is a hemiacetal, since it is 

formed by combination of an aldehyde

and an alcohol group. 

Similarly, the ring structure of a ketose

is a hemiketal.  The cyclic

 
structure is retained in solution, but isomerism (
C
6

H
12

O
6

)
occurs 

about position 1, the carbonyl or anomeric

carbon atom, to give

 
a mixture  of α‐glucopyranose

(38%) and β‐glucopyranose

(62%). 

32. •

The cyclic α

and β

anomers

of a sugar in
solution are in equilibrium with each other,
and can be spontaneously interconverted

(a process called mutarotation)

33. :  Epimers 4. 
Isomers differing  as a result of variations in configuration  of 

the OH and H on carbon atoms 2, 3, and 4 of glucose are known

 
as epimers.   Biologically, the most important epimers

of 

(
C
6

H
12

O
6

) glucose  are mannose and galactose, formed by 

epimerization at carbons 2 and 4, respectively. 

34. Epimers of glucose
D-

glucoseD-

galactose
Epimer at C4
D-

mannose
Epimer at C2

35. isomerism:  ketose ‐ Aldose 5. 
Fructose  has the same molecular  formula as glucose 

(C
6

H
12

O
6

) but differs in its structural  formula,  since there is  keto

group in position 2, the anomeric

carbon of fructose,  whereas 

there is  aldehyde

group in position 1, the anomeric

carbon of 

glucose

36. Are Physiologically Important: Monosaccharides Many 

xylose ,  ribulose ribose,  e.g: Pentoses 1 

, fructose, mannose galactose glucose,  :  Hexoses ‐2
) are formed as metabolic  sedoheptulose ( carbon sugar  ‐ seven ‐3

intermediates  in  the pentose phosphate pathway.
g  carboxylic acid derivatives of glucose are important, includin ‐4
formation  and in  glucuronide (for  glucuronate ‐D
a. 

glycosaminoglycans) 
) glycosaminoglycans (in  iduronate ‐L
b. 
acid pathway) theuronic (an intermediate in  gulonate ‐L
c. 

39. Derived Sugars
Sugars: Deoxy 1. 
Lack an Oxygen Atom =Deoxy

sugars are those in which a hydroxyl 

group has  been replaced by hydrogen.    Examples: 
a. deoxyribose

in DNA. 
b. L‐fucose

occurs in glycoproteins.
c. 2‐deoxyglucose  is used experimentally as an inhibitor of glucose 

metabolism..

40. ): Hexosamines 2. Amino Sugars (
Are compounds in which OH at C2 is replaced by NH2 
1. D‐glucosamine, a constituent of hyaluronic

acid , 
2. D‐galactosamine(chondrosamine), a constituent of chondroitin; 
3.  Several  antibiotics (eg, erythromycin) contain  amino sugars 
believed to be important for their antibiotic activity
Galactosamine

41. 3.Sugar acids
1.1.

Produced by oxidation of Produced by oxidation of
carbonyl carbon to carboxylic carbonyl carbon to carboxylic
group. group.
2.2.

Or by oxidation of last hydroxyl Or by oxidation of last hydroxyl
carbon to carboxylic group. carbon to carboxylic group.
3.3.

Or by oxidation of both. Or by oxidation of both.

42. 1.Aldonic 1.Aldonic
CHO
COH H
CH HO
COH H
COH H
CH
2
OH
COOH
COH H
CH HO
COH H
COH H
CH
2
OH
bromine water, O
2
D-Gluconicacid D-Glucose

43. Uronic Uronic --22
CHO
COH H
CH HO
COH H
COH H
CH
2
OH
CHO
COH H
CH HO
COH H
COH H
COOH
Dil. Nitric acid
D-Glucuronicacid D-Glucose
H
2
O
2

44. Aldaric Aldaric --33 CHO
COH H
CH HO
COH H
COH H
CH
2
OH
COOH
COH H
CH HO
COH H
COH H
COOH
Conc. Nitric acid
D-Glucaricacid D-Glucose
O
2

45. Glycoside Formation
•

The hemiacetal

and hemiketal

forms of
monosaccharides

can react with alcohols
to form acetal

and ketal

structures called
glycosides. The new carbon-oxygen bond
is called the glycosidic

linkage.

46. Acetal Glycosides=
The OH of anomeric

carbon of monosaccharides

can react with either: 
1‐

Nitrogen of amines

(The anomeric

carbon atom of sugar can be 

linked  to the nitrogen atom of an amine by N‐

glycosidic

bond) e.g

OH 

of ribose linked  to nitrogen  of nitrogenous base to form nucleotides. 

47. OH of other -2
compound :
•

A-

May be carbohydrate

(
Monosaccharides

can be linked to
each other by O-

glycosidic

bonds to
form disaccharides, oligosaccharides
and polysaccharides).
•

(monosaccharide+
monosaccharide)=hemiacetal+hemia

cetal=acetal.
•

b-

May be non carbohydrate

e.g

glycolipid, glycoprotein.
•

The non carbohydrate component of
a glycoside is called aglycone.

48. O-

and N-glycosides
•

If the group on the non-
carbohydrate molecule
to which the sugar is
attached is an -OH
group, the structure is an
O-glycoside
•

All sugar-sugar
glycosidic

bonds are O-
type linkages

49. O-

and N-glycosides
•

If the group is an -NH2 ,
the structure is an N-
glycoside
–

purines

and pyrimidines
(found in nucleic acids),
–

aromatic rings (such as
those found in steroids and
bilirubin),
–

proteins (found in
glycoproteins

and
glycosaminoglycans),

50. Naming glycosidic

bonds
•

Glycosidic

bonds
between sugars are
named according to
–

numbers of the
connected carbons (1-4,
1-6),

and
–

position of the
anomeric

hydroxyl
group of the sugar
involved in the bond.

51. Naming glycosidic

bonds
•

this anomeric

hydroxyl
group is in the α

configuration, the
linkage is an α-bond.
•

If it is in the β

configuration, the
linkage is a β-bond.

52. Naming glycosidic

bonds
•

Lactose, for example, is
synthesized by forming a
glycosidic

bond between carbon
1 of β-galactose

and carbon 4 of
glucose.
–

The linkage is, therefore:
β(1 →4)

glycosidic

bond.
•

Because the anomeric

end of the
glucose residue is not involved in
the glycosidic

linkage it (and,
therefore, lactose) remains a
reducing sugar.

54. Naming of  O‐

glycosidic

bond() carbohydrate and carbohydrate ‐

Glycosidic

bonds between  sugars are named  according to:
1‐

The numbers of the connected carbons  
2‐

The position of the anomeric

hydroxyl  group  of the sugar.
If the anomeric

hydroxyl  group is in α

configuration  the link is α‐

bond and if it’s   in β, the link is β‐

bond. Examples
In lactose 
β

1 of galactose

bind to C4 of glucose by  β

1 

→4 

galactosidic

bond.

55. Examples of glycosides: 1‐

Disaccharides as maltose, lactose and sucrose
2‐

Polysaccharides.
3‐

Glycolipids.
4‐Glycoproteins.(may be O‐

or N‐

glycosidic

link)
5‐Nucleotides as ATP, GTP,  UTP where  aglycon

is purine

or 

pyrimidine

bases       (N‐

glycosides)
The glycosides  that are important  in medicine 
1. cardiac  glycosides all contain  steroids as the aglycone.
2. Other  glycosides include antibiotics such as streptomycin.

56. Disaccharides
‐

Disaccharide consists of two sugars joined by an O‐

glycosidic

bond.
‐

The most abundant disaccharides are sucrose, lactose and maltose.
‐

Other disaccharides include  isomaltose, cellobiose

and trehalose.
‐The disaccharides can be classified  into homo  disaccharides and 

hetero disaccharides.  
‐A) Homo disaccharides
: are formed of the same monosaccharide units 

and include  maltose, isomaltose, cellobiose

and trehalose.
‐(B) Hetero disaccharides
: are formed of different  monosaccharide 

units and include: sucrose, lactose.  

57. Lactose: Lactose: It is formed of

-galactose

and

-glucose linked by

-1,4-glucosidic linkage
Contain free anomeric

carbon so reducing sugar
It may appear in urine in late pregnancy and during
lactation.
O
OH
H
H
H
OH H
OH
CH
2
OH
H
O
H
OH ..... H
H ..... OH
H
OH H
OH
CH
2
OH
H
and Lactose
-GalactoseGlucose
1
4
O

58. Sucrose Sucrose
•

α

D-glucopyranose

and
β

D fructofuranose

by α
1-

2 glycosidic

bond
•

No free aldehyde

or
keton

gp

so non
reducing sugar
•

hydrolysed

to glucose
and fructose by sucrase
(invertase) enzyme.
•

* Sucrose is
dextrorotatory +66.5.
O
H
OH
H
H
OH H
OH
CH
2
OH
H
1
Sucrose
-Glucose
-Fructose
CH
2
O
H
O
H
CH
2
OH
OHH
H
OH
O
2

59. Maltose (malt sugar): Maltose (malt sugar):
It consists of 2 It consists of 2 --glucose units linked by glucose units linked by
--1,41,4--glucosidic linkage, glucosidic linkage, Contain free anomeric

carbon so reducing sugar.
O
H
OH
H
H
OH H
OH
CH
2
OH
H
O
H
OH ..... H
H ..... OH
H
OH H
OH
CH
2
OH
H
O
and Maltose
-GlucoseGlucose
1
4

60. B. B. Trehalose Trehalose
::
It is formed of 2

-glucose units linked by

-1,1-
glucosidic linkage. Not Contain free anomeric
carbon so non reducing sugar
Present in a highly toxic lipid extracted from
Mycobacterium tuberculosis.
O
H
OH
H
H
OH H
OH
CH
2
OH
H
O
HH
OH
HO H
2
C
H
OH H
OHH
O
1 1
T
r
ehalose
-Glucose-Glucose

61. Disaccharides ComponentsReduction
1-

sucrose =
cane sugar
= beet sugar =
table sugar
α

D-
glucopyranose
and β

D
fructofuranose.
by α

1-

2
glycosidic

bond
No free
aldehyde

or
keton

gp

so
non reducing
sugar
hydrolysed

to
glucose and
fructose by sucrase
(invertase) enzyme.
* Sucrose is
dextrorotatory
+66.5.
2-

Lactose (milk
sugar)
β

D galactose
and α

D glucose.
by β

1-4
glycosidic

bond
Contain free
anomeric
carbon so
reducing
sugar
* It may appear in
urine in late
pregnancy and
during lactation.

62. Disaccharides*Components Bond Reduction
1-

Maltose 2αD-glucose α

1-4 glycosidicContain free
anomeric
carbon so
reducing sugar.
4-

Trehalose2αD-glucose α

1-1 glycosidicNot Contain
free anomeric
carbon so non
reducing sugar

63. Oligosaccharides
•

Oligosaccharides contain from 3 to 10
monosaccharide units.
•

Raffinose

An oligosaccharide found in
peas and beans

64. Polysaccharides (glycans)
‐

Polysaccharides consist  of more  than 10 monosaccharide units and / 

or their derivatives
Classification According to structure:
1‐

Homo polysaccharides  (Homo glycans): 
contain only one type of 

monosaccharide molecule.
E.g. starch, glycogen,  dextrin, cellulose, inulin

and chitin
2‐

Hetero  polysaccharides
: contain more than one type of 

monosaccharides. 
E.g. glycosaminoglycan, glycoprotein.

65. 1. Starch
‐

is a homopolymer

of glucose forming an α‐

glucosidic

chain, called a 

glucosan

or glucan. 
‐It is the most abundant dietary carbohydrate in cereals, potatoes, 

legumes,  and other  vegetables. 
‐The two main constituents are amylose

(15–20%), which has a 

nonbranching

helical structure) and amylopectin
(80–85%), which consists of branched chains composed of 24–30 
glucose residues  united by 1 →4linkages  in the chains and by 1 →6 

linkages  at the branch points.
:Dextrins 2. 
Are intermediates in the hydrolysis of starch.

67. ••

Amylose Amylose::. .
Straight chain compound Straight chain compound
present in the form glucose units present in the form glucose units
linked by linked by --1,41,4--glucosidic bond of a glucosidic bond of a
helix formed of a large number of helix formed of a large number of --

glucose. glucose.
O
H
H
H
OH H
OH
CH
2
OH
H
O
H
H
OH H
OH
CH
2
OH
H
O
Amylose
1
4
n
O
O
14
It forms the inner part of starch granules

69. : Glycogen
3. 
‐

is the storage polysaccharide in animals.
‐

It is a more  highly branched structure than  amylopectin, with chains 

of 12–14 α‐D‐glucopyranose

residues  in α[1 →4]‐glucosidic linkage),

with branching by means  of α(1 →6)‐glucosidic bonds
:
Inulin
4.  
is a polysaccharide of 
FRUCTOSE

(and hence a fructosan)
found in plants.
It is readily soluble in water .
is used to determine the glomerular

filtration rate.

70. Cellulose 
5. 
‐Is the chief constituent of the framework of plants. 
‐It is insoluble
‐consists of β‐D‐glucopyranose

units linked  by β(1 →4) bonds to form 

long, straight chains strengthened  by cross‐linked  hydrogen bonds. 

Cellulose cannot  be digested by mammals because of the absence
of an enzyme that hydrolyzes the β

linkage.  It is an important
source of “bulk”

in the diet. So prevent constipation.
‐
Starch
Cellulose

71. 6. Chitin 
is a structural  polysaccharide in the exoskeleton  of crustaceans

and insects  and also in mushrooms. 
It consists of N‐acetyl‐D‐glucosamine

units joined by
β

(1 →4)‐glycosidic

linkages

72. Glycosaminoglycans

(GAGs)
(Mucopolysaccharides)
‐

Glycosaminoglycans

are long linear  (unbranched) 

heteropolysaccharide

chains generally composed of a repeating 

disaccharide unit (acidic sugar‐amino sugar)n. 
‐The 

amino 

sugar 

is 

either 

D‐glucosamine

or 

D‐galactosamine

in 

which  

the 

amino 

group  

is 

usually 

acetylated, 

and 

sometimes 

sulphated.
There  are 6 types: 
1. heparin.               2. heparan

sulphate.         3. dermatan

sulphate
4. keratan

s             5. Chondroitin

s                  6. hyaluronic

acid

73. ) mucopolysaccharides ( Glycosaminoglycans
All of the glycosaminoglycans

except hyaluronic

acid and heparin are 

found covalently attached to protein, forming proteoglycan

monomers.
Their  property of holding large  quantities of water and occupying 

space lubricating  other structures, is due to the large  number  of OH 

groups and negative charges on the molecules, which, by repulsion, 

keep the carbohydrate chains apart. 

74. Glycoproteins
‐Are proteins to which oligosaccharides  are covalently attached.
‐

Oligosaccharide chains  formed mainly  of  sialic

acids  and L‐fucose.
‐

Sialic

acids are N‐

or O‐derivatives  of neuraminic

acid .
‐

Neuraminic

acid is a nine‐carbon sugar derived from  mannosamine

and pyruvate.

75. •

Glycoproteins

have many functions: •

1-

Soluble as enzymes, hormones and
antibodies.
•

2-

In lysosomes
•

3-

attached to the cell membrane (The
membrane bound glycoproteins) participate
in:
–

a-

cell surface recognition (by other cells,
hormones, viruses)
–

b-

Cell surface antigenicity

(as blood gp
antigens)

76. Proteoglycans
Glycoprotein
Carbohydrate components

Glycosaminoglycans
-

Repeating disaccharide unit
-

Linear (unbranched)
-

long
-

Contain uronic

acids (glucuronic
and iduronic
-

N-

acetyl hexosamine
-

Contain hexoses

as galactose

(in
keratin sulphate)
-

contain sulphate
-

No pentoses
-

No deoxy

sugar
Oligosaccharides
-

No repeating units
-

Branched
-short -

contain sialic

acid derivatives
(NANA) -

N-

acetyl hexasamine
-

Contain hexoses

as galactose
and mannose -No sulphate -

Contain pentose
-Contain deoxy

sugar as L-fucose

77. 2-

Tissue distribution and functions
Structural
-

Cartilage
-

Bone
-

Tendons
-

Cell membrane
-

Cornea
Functional and structural
-mucines
-

Blood groups antigens
-

some hormones
-enzymes
-

Immunoglobulins

and
receptors

78. Acid Neuraminic - Acetyl – NANA=N
-

Neuraminic

Acid=sialic

acid = mannosamine
+ pyruvic

acid
= amino sugar acid
-

NANA found in glycoproteins.

79. Fucose -L
galactose -L–deoxy - = 6
=Methyl pentose
Found in glycoprotein

80. THE END!
Thank You