Carbohydrate 1

1. Carbohydrates
Prof. Dr. Khalid Hussain

2. Leaning objectives
• General introduction
• Medicinal and Pharmaceutical Importance
• Chemistry
• Classification

3. Introduction
• Chemically: Polyhydroxy aldehydes and
ketones, having hydrogen and oxygen in a ratio
of water (2:1)
e.g. Ribose (C5H10 O5) and Glucose (C6H12 O6)

4. • General formula Cn(H2O)n, hence, also
called hydrates of carbon
• Also include substances, which upon
hydrolysis produce polyhydroxy
aldehydes and ketones

5. Importance of carbohydrates
• Major source of energy (4.1C)
• Serve as stored forms of energy as
glycogen in;
–Liver
–muscles

6. • Involved in recognition processes of
immunoglobulins
• Are important components of brain cells e.g.
neuraminic acids, cerebrosides (Glycolipids)
and gangliosides
• Are important component of nucleic acids e.g.
pentose sugar ribose and deoxyribose

7. Contn’d
• Flavouring agents
• Sweetening agents
• Binders in tablets
• Disintegrators in tablets

8. Contn’d
• Function as anticoagulant (Heparin)
• Plasma expanders (Dextran)
• Part of parenteral nutrition
• Used as Dietary fibers e.g. Cellulose
• Protein sparing action
• Decrease breakdown of fatty acids, thus
prevent ketosis

9. • Used in analytical techniques: paper
chromatography, Agar-agar and starch

10. Classification
• Carbohydrates have been classified
into 4 main groups;
–Monosaccharides
–Disaccharides
–Oligosaccharides
–Polysaccharides

11. Monosaccharides
• Carbohydrates which can’t further be broken down
into simpler units by hydrolysis
• Classified according to the number of carbon atoms
present in them
– For example trioses, tetroses and hexoses

12. • Usually have 3-9 carbon atoms
• Further sub-classified into
– aldoses and ketoses
• Exact name is based on:
– number of carbons atoms &
– presence of aldehyde or ketone group
– i.e aldotriose or ketotriose

13. Aldotrioses/
Ketotrioses
C3H6O3 Glyceraldehyde and dihydroxy
acetone
Aldotetroses/
Ketotetroses
C4H8O4 Erythrose, Erythrulose
Aldopentoses/
Ketopentoses
C5H10O5 Ribose, Ribulose
Aldohexoses/
Ketohesoses
C6H12O6 Glucose, Fructose
Erythrose Ribose Ribulose

14. • Monosaccharides also include derivatives of
above mentioned monosaccharides e.g.
– amino sugars
– sugar alcohols
– sugar acids
– sugar esters of sulfuric acid
– sugar esters of phosphoric acid

15. Disaccharides
• Biose
• Formed when two monosaccharides undergo
a condensation reaction, which involves the
elimination of a water molecule
Sucrose

16. Oligosaccharides
• Greek word oligos, meaning "a few" and
sacchar meaning "sugar“
• Saccharide polymers containing a small
number (typically 3 to 10) of component
sugars- monosaccharaides
For example Raffinose

17. Polysaccharides
• Polymeric carbohydrate structures, formed
by repeating units (either mono- or di-
saccharides) joined together by glycoside
bond
• Such structures are often linear, but may
contain various degrees of branching
• Polysaccharides are often quite
heterogeneous, containing slight
modifications of the repeating units

18. • When all the monosaccharides in a
polysaccharide are of same type the
polysaccharide is called a
homopolysaccharide: starch and glycogen, but
when more than one type of monosaccharides
are present, they are called
heteropolysaccharides: pectin and lignin
• Polysaccharides have a general formula of
(C6H10O5)n
• Not sweet, hence called non-sugars

19. H O
OH
H
OHH
OH
CH2OH
H
O H
H
OHH
OH
CH2OH
H
O
HH H O
O
H
OHH
OH
CH2OH
H
H H O
H
OHH
OH
CH2OH
H
OH
HH O
O
H
OHH
OH
CH2OH
H
O
H
1
6
5
4
3
1
2
amylose
cellulose
H O
OH
H
OHH
OH
CH2OH
H
O
H
OHH
OH
CH2OH
H
O
H H O
O H
OHH
OH
CH2OH
H
H O
H
OHH
OH
CH2OH
H
H
OHH O
O H
OHH
OH
CH2OH
H
O
H H H H
1
6
5
4
3
1
2
Upon acid hydrolysis produce monosaccharides

20. Oxidation of glucose
• Mild oxidizing agents such as bromine water convert
glucose to gluconic acid, which is a single step
reaction
• This reaction is used to differentiate sugars having –
CHO (reducing) group and those yielding such group

21. Example is Fehling's solution test
• Fehling's solution is composed of equal parts
of two solutions:
1-Fehling's solution A
69.28 g copper sulfate pentahydrate
dissolved in 1 litre of distilled water
2-Fehling's Solution B
346 g potassium sodium tartrate and 120 g
sodium hydroxide in 1 litre of distilled
water

23. • Under alkaline conditions fructose is converted
to glucose and mannose
Fructose also give positive test

24. Tollens' reagent test "silver mirror"
• Tollens' reagent: when silver nitrate solution is
treated with NaOH, it forms precipitate and
then NH4OH is added till the precipitate is
dissolved-[Ag(NH3)2]+
• The diammine silver complex is an oxidizing
agent, which is itself reduced to silver metal