Carbohydrates can be classified into 4 main groups: 1) Monosaccharides which include simple sugars that cannot be further broken down, such as glucose and fructose. 2) Disaccharides formed from two monosaccharides joined together like sucrose. 3) Oligosaccharides containing 3-10 monosaccharide units such as raffinose. 4) Polysaccharides consisting of long chains of monosaccharide units like starch, cellulose, and glycogen. Carbohydrates serve important functions like energy storage, structural support, and participating in biological processes. They can be identified using chemical tests like Fehling's solution which detects the presence of reducing

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