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1. CARBOHYDRATES

2. LECTURE OUTLINE
By the end of the lecture, the student
should know:
 The Importance of carbohydrates.
 The Definition of Carbohydrates.
 The Classification of Carbohydrates.
 Structure of glucose

3. EXAMPLES OF CARBOHYDRATES
 GLUCOSE
 FRUCTOSE
 SUCROSE
 STARCH
 CELLULOSE
 LACTOSE
 MALTOSE
Carbs
Protein
Fats
Carbohydrates are grains, fruits, vegetables, legumes and sugar

4. AN ATEMPT TO DEFINE
CARBOHYDRATES
Carbohydrates or Saccharides
(Greek Sakcharon meaning "Sugar")
 CARBOHYDRATES ARE THE HYDRATES OF CARBON
HAVING GENERAL FORMULA Cx(H2O)y AND CONTAINING
CARBON , HYDROGEN AND OXYGEN BUT IS
THIS TRUE !!!!!!!!!!

5. Carbohydrates derive their name from a
Misleading Concept
'Hydrates of Carbon’
LIMITATION OF THE DEFINITION
Cx(H2O)y
 FORMALDEHYDE (HCHO), ACETIC ACID (CH3COOH) ARE
NOT CARBOHYDRATE
 FEW CARBOHYDRATE LIKE RHAMNOSE (C6H12O5), DEOXY
RIBOSE (C5H10O4) DO NOT FITS INTO THE DEFINITION
 MOREOVER CARBON IS NOT KNOWN TO FORM HYDRATES

6. MODERN DEFINITION OF
CARBOHYDRATES
 CARBOHYDRATES ARE DEFINED AS OPTICALLY
ACTIVE POLY HYDROXY ALDEHYDES OR POLY
HYDROXY KETONES OR THE COMPOUNDS
WHICH YIELD SUCH UNIITS ON HYDROLYSIS

7. CLASSIFICATION OF CARBOHYDRATES
SUGARS (sweet in
taste) NON SUGARS (not
sweet on taste)
Monosaccharides
(ALDOSE/KETOSE)
( simplest
carbohydrates
which cannot be
further hydrolyzed
and have C3 to C7)
e.g. glucose,
fructose, ribose,
glyceraldehyde etc.
Oligosaccharides
(Hydrolyzed to give 2-10
monosaccharides on
hydrolysis)
e.g. Disaccharide :- Sucrose,
Maltose, Lactose
Trisaccharide:- Raffinose
C12H22O11+H2O (H+) 
C6H12O6 + C6H12O6
Polysaccharides
(Hydrolyzed to give a
larger number of
monosaccharides) e.g.
Starch, Cellulose,
glycogen, gums etc.
(C6H10O5)n+ nH2O
(Starch)
nC6H12O6

8. No. of carbon
atoms
General
terms
Aldehydes Ketones
3 Triose Aldotriose
(glyceraldehyde)
Ketotriose
(dihydroxyacetone)
4 Tetrose Aldotetrose
(2,3,4-trihydroxybutanal)
Ketotetrose
5 Pentose Aldopentose
(ribose)
Ketopentose
6 Hexose Aldohexose
(Glucose, galactose, mannose)
Ketohexose
(fructose)
7 heptose Aldoheptose ketoheptose
Monosaccharides (ALDOSE/KETOSE)
Sugars: Monosccharides and disaccharides are collectively called as sugars.
They are sweet and soluble in water. E.g. glucose, fructose, cane sugar etc.
Non-sugars: Polysaccharides are tasteless and insoluble in water. E.g. starch,
cellulose
MONOSACCHARIDES ARE POLY HYDROXY ALDEHYDES OR KETONES WHICH
CANNOT BE FURTHER HYDROLYSED TO GIVE SIMPLE UNITS
8

9. CARBOHYRATES
REDUCING SUGARS
Carbohydrates that reduce
Fehlings solution and Tollens
reagent
Example:-
All the monosaccharides
Disaccharide (Maltose and
lactose)
NON REDUCING
SUGARS
Carbohydrates which donot
reduce Fehlings solution and
Tollens reagent
Example :-
All polysaccharides
Disaccharides (Sucrose)

10. Disaccharides
C12H22O11
H2O
H+
C6H12O6 + C6H12O6
C12H22O11
H2O
H+
C6H12O6 + C6H12O6
C12H22O11
H2O
H+
C6H12O6 + C6H12O6
Sucrose
Lactose
Maltose
Glucose
Glucose Galactose
Glucose Glucose
10
CARBOHYDRATES THAT YIELD 2 TO 10 MONO SACCHARIDE UNITS
ON HYDROLYSIS ARE CALLED OLIGOSACCHARIDES.
EXAMPLE :- DISACCHARIDE, TRISACCHARIDE , TETRASACCHARIDE
ETC.
Fructose

11. POLYSACCHARIDES
 These are the carbohydrate that yield a
large number of monosaccharide units
(greater than 10) on hydrolysis.
 Starchis a Polymer of α-glucose and digested by human beings
 Celluloseis a polymer of β-glucose and not digested by human beings.
 Glycogen:- Animal starch (carbohydrate stored in animal body)
 Non sugars are generally :-
 Tasteless
 Amorphous solids
 Insoluble in water to form colloidal suspension

12. STRUCTURE OF GLYCERALDEHYDE,
GLUCOSE, FRUCTOSE, GALACTOSE.

13. GLUCOSE (DEXTROSE SUGAR)
 Monosaccharide
 Sweet, reducing sugar
 Found in fruits, honey, ripe grapes
 Also called grape sugar
 Aldohexose, also called dextrose
 Preparation of Glucose :-
 From acid hydrolysis of sucrose (Cane sugar)
 From acid hydrolysis of Starch
 From Maltose and Lactose

14. DETERMINATION OF STRUCTURE OF
GLUCOSE
 Molecular formula :- C6H12O6
 Earlier it was thought that it have open chain
structure having:-
 One aldehyde (-CHO) functional group
 One primary alcohol (-CH2OH)
 Four secondary alcohols (-CHOH)

24. Confirmation of open chain and cyclic structure of glucose
Open chain structure Cyclic structure
The open chain structure can be
confirmed on the basis of the
following reactions which show
the presence e of free aldehydic
group.
1. Glucose reduces tollen’s and fehling
reagents
2. It reacts with con.HNO3 to give
gluconic acid.
3. It reacts with Hydroxylamine and
Hydrogen cyanide.
4. It reacts with HI to give normal
hexane confirming the presence of
six carbon atom in a linear chain.
The following reactions confirm the
presence of ring structure:
1. Glucose does not give 2,4-DNP test,
Schiffs test and also does not react
with sodium hydrogen sulphite.
2. Pentaacetate of glucose does not
react with Hydroxylamine indicating
the absence of –CHO group
3. Mutarotation: “Spontaneous
change in the specific rotation of an
optically active compound”
α-D-(+) Equilibrium β -D-(+)
Glucos
e
glucos
e
mixtur
e
+1110 +52.50 +19.2
0
24

25. CHO
OH
H
H
HO
H
HO
CH2OH
H
HO
L-glucose
CHO
H
HO
OH
H
OH
H
CH2OH
OH
H
D-glucose
1
2
3
4
5
6
Open Structures CH2OH
H
HO
OH
H
OH
H
CH2OH
D-fructose
1
2
3
4
5
6
C=O
25

26. ANOMERS
 The pair of stereoisomers which differ in
configuration only around C1 atom are called
anomers and the C1 carbon atom is called as the
Anomeric carbon/ Glycosidic carbon

27. Ring structures of Glucose
O
CH2OH
5
OH
OH
HO
OH
H
H
H
H 1
2
3
4
6
H
O
CH2OH
OH
H
5
OH
HO
OH
H
H
H
1
2
3
4
6
6
OH
H
1
2
3
4
5
1
2
3
4
OH
H
OH
H
6
5
α-D-(+)glucopyranose
β -D-(+)glucopyranose
Fischer projection Haworth structure
27