1. Carbohydrates
Dr. Khalid Hussain

2. Introduction
• Chemically: Polyhydroxy aldehydes and ketones
• Have hydrogen and oxygen in a ratio of water
(2:1)
Ribose (C5H10O5) and Glucose (C6H12O6)

3. • General formula Cn(H2O)n.Hence, also
called hydrates of carbon
• Substances which are converted into
polyhydroxy aldehydes and ketones
after hydrolysis

4. Importance of carbohydrates
• Provide major source of energy (4.1C)
• Serve also as stored forms of energy as
glycogen in liver and muscles
• Protein sparing action
• Reduce breakdown of fatty acids and
preventing ketosis
• Involved in biological recognition processes of
immunoglobulin

5. Contn’d
• Flavoring and Sweetening agents
• Dietary fiber (Cellulose)
• Important components of brain cells as
neuraminic acids, cerebrosides (Glycolipids)
and gangliosides
• Important component of nucleic acids as
pentose sugars - ribose and deoxyribose

6. Contn’d
• Function as physiological anticoagulant
(Heparin)
• Plasma expanders (Dextran)
• Parenteral nutrition
• Binders in tablets
• Disintegrators in tablets
• Analytical techniques: Agar agar and starch
• Diagnostic markers

7. Classification
• Have been classified into 4 main
groups
– Monosaccharides
– Disaccharides
– Oligosaccharides
– Polysaccharides

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

9. • 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 groups
– i.e aldotriose or ketotriose

10. Aldotrioses/ C3 H 6 O 3 Glyceraldehyde and dihydroxy
ketotrioses acetone
Aldotetroses/ C4 H 8 O 4 Erythrose, Erythrulose
ketotetroses
Aldopentoses/ C5H10O5 Ribose , Ribulose
ketopentoses
Aldohexoses/ C6H12O6 Glucose, Fructose
ketohesoses
Erythrose Ribose Ribulose

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

12. Disaccharides
• Biose
• Formed when two monosaccharides undergo
a condensation reaction which involves the
elimination of a small molecule, such as
water, from the functional groups only
Sucrose

13. Oligosaccharides
• Greek word oligos, meaning "a few", and
sacchar which means "sugar“
• Saccharide polymers containing a small
number (typically three to ten) of component
sugars- Monosaccharides
For example Raffinose

14. 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 unit

15. • 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, lignin
• Polysaccharides have a general formula of
(C6H10O5)n
• Not sweet, hence called non-sugars

16. CH2OH 6CH OH CH2OH CH2OH CH2OH
2
O 5 O H O H O H H O H
H H H H H
H H H H H
OH H 1 4 OH H 1 OH H OH H OH H
O O O O OH
OH 2
3
H OH H OH H OH H OH H OH
amylose
CH2OH 6CH OH CH2OH CH2OH CH2OH
2
O 5 O O H O H O OH
H H H
H H H H H
OH H 1 O 4 OH H 1 O OH H O OH H O OH H
OH H H H
H 2 H
3
H OH H OH H OH H OH H OH
cellulose
Upon acid hydrolysis produce monosaccharides

17. Significance
• Key role in maintaining energy balance in the
biosphere
• Building blocks and source of energy
• Used as excipients in pharmaceuticals
Dusting Powders, disintegrant, mucilage
• Bio-markers
• As Medicine –heparin, glucose, dextran etc.
• Chromatography and electrophoresis

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

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

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

22. Tollens' reagent test "silver mirror"
• Tollens' reagent: when silver nitrate solution is
treated with sodium hydroxide(NaOH) till 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