Carbohydrates are the most abundant class of biomolecules. They are composed of carbon, hydrogen, and oxygen and can be classified as monosaccharides, oligosaccharides, or polysaccharides depending on the number of monosaccharide units joined together. Monosaccharides exist as either open-chain or cyclic structures and include aldoses and ketoses. Carbohydrates serve important functions such as energy storage, structure, and defense. They exhibit properties like stereoisomerism, optical activity, and anomerism due to their chiral nature.

1. Carbohydrates
MAN BAHADUR RANA
BPH
ACAS,NEPAL

2. Carbohydrates
• Most abundant class of biomolecules
• Composition: carbon, hydrogen and
oxygen and hydrogen and oxygen ratio of
2:1. C6 H12O6. or Cx(H20)y.
• Originally produced through CO2 fixation
during photosynthesis

3. Defination
polyhydroxyaldehydes or ketones or compounds
which produce them on hydrolysis.
saccharides
hydrate of Carbon (CH2O)n

4. Function
1. Energy:
2. Storage of energy:
3. Structure:
4. Defense:
5. To confer cells specificity:
6. Lubrication:

5. Classificationn of
Carbohydrates
• monosaccharides,oligosaccharides and
polysaccharides
• Monosaccharides (simplest sugars)
cannot be broken down into simpler
sugars under mild conditions. Eg
trioses, pentoses,

6. Monosaccharides
• Polyhydroxy ketones (ketoses) and
Polyhydroxyaldehydes (aldoses)
• Generally Ketose named for “equivalent aldose” +
“ul” inserted
• Triose, tetrose, etc. denotes number of carbons
•
• Empirical formula = (CH2O)n

7. Monosaccharides
• Open chains free aldoses or ketoses
• As the two reacting groups aldehyde or ketone and alcoholic
group belong to the same molecule
• Condensation of the aldehyde group on carbon 1(carbon 2
in ketone group) with the alcoholic OH group on carbon 5
takes place  closed chain

8. "a few" - usually 2 to 10  on hydrolysis.
monosaccharides joined together by covalent
bonds known as glycosidic bond.
Disaccharides[maltose(GG),
Lactose(GGa),Sucrose(GF)
trisaccharides[Raffinose(GaGF, Melezitose(GFG)]
etc
Oligosaccharides

9. Oligosaccharides

10. Polysaccharides/Glycan
• A combinationn of many monosaccharides linked
by glycosidic bonds
• They are of high molecular weight (up to a
million).
• They are usually tasteless( non-sugars)and form
colloids with water.

11. Polysaccharides/Glycan
• homopolysaccharides(Starch,Glycogen)
• heteropolysaccharides (Proteoglycan, Hyaluronic
acid, Chondriotin-4-Sulphate)

12. Polysaccharides/Glycan
Glycogen

13. Polysaccharides/Glycan
• Glycosamin
• glycosaminoglycans (GAG) or
mucopolysaccharide repeating units of
sugar derivatives amino sugar and uronic
acids eg Hyaluronic acid, heparin

14. Properties of Carbohydrates
Physical Properties
Stereoisomerism
Optical Activity
Anomerism

15. Sterioisomerism
• Sterioisomers or Isomers same molecular
formula and same structure, but differ
arrangement of their atoms in space.
• asymetric or chiral carbon (n) no. of
isomers 2n

16. Sterioisomerism
•The mirror imaged isomers enantiomers.
•D or L on the basis of orientation of H and OH on the carbon atom
adjacent to the terminal primary alcoholic group
•Pairs of isomers  opposite configurations at one or more
chiral centers but are NOT mirror images  diastereomers
•Epimers = Two sugars differ in configuration  one chiral
carbon only
C
C*
O
C*
C*
C*
CH2OH
H OH
HO H
H OH
H OH
H
C
C*
O
C*
C*
C*
CH2OH
HO H
H OH
HO H
HO H
H
C
C*
O
C*
C*
C*
CH2OH
H OH
HO H
H OH
H OH
H
C
C*
O
C*
C*
C*
CH2OH
HO H
HO H
H OH
H OH
H
C
C*
O
C*
C*
C*
CH2OH
HO H
HO H
H OH
H OH
H
C
C*
O
C*
C*
C*
CH2OH
H OH
HO H
HO H
H OH
H
D-glucoseL-glucose
Enantiomers
D-glucose D-mannose
Epimers
D-mannose D-galactose
Diastereomers

17. Optical Activity
a beam of plane-polarized light  a solution rotation of
light  rightdextrorotatory (d or + sign)
leftlaevorotatory (l or - sign).
The compounds  the optical isomers or enantiomorphs .

18. Fischer and Hawarth Formula
• The Planar structure  Fischer formula.
• But due to the strain in the backbone carbon
 assume ring structure Hawarth
Formula

19. Fischer and Hawarth Formula

20. Anomers and Anomeric Carbon
Carbon 1 or 2(hemiacetal or hemiketal)after
cyclization asymmetric  anomeric carbon.
fischer formula
OH  right of anomeric carbon α form
OHleft of anomeric carbonβ form
hawarth formula
OH groupdown of anomeric carbon α form
OH group β form.
These forms are called anomers.

21. Amino Sugars

22. Deoxy Sugars
Deoxy Sugars Lack an Oxygen Atom