intoduction to carbhohydrates, biochemistry

2. DEFINITION
THEY ARE ALSO CALLED SACCHARIDES, ARE MOST
ABUNDANT BIOLOGICAL MOLECULES CONTAINING C,
H AND O, WHICH ARE COMBINED IN THE RATIO OF 2:1
(CH2O) N

3. CLASSIFICATION
CARBHOHYDRATES
MONOSACCHARIDE
ALDOSES
KETOSES
DISACCHARIDES
REDUCING
NON-REDUCING
POLYSACCHARIDES
HOMOPOLYSACCHARIDES
HETEROPOLYSACCHARIDES

4. MONOSACCHARIDES
• MOLECULES HAVING ONLY ONE ACTUAL OR POTENTIAL SUGAR GROUP
ARE CALLED MONOSACCHARIDES. THEY CANNOT BE FURTHER
HYDROLYSED INTO SMALLER UNITS.
• MONOSACCHARIDES ARE SIMPLE SUGARS, WHICH CAN JOIN IN SEVERAL
WAYS TO FORM DI, OLIGO AND POLYSACCHARIDES.
• THESE ARE THE ALDEHYDE OR KETONE DERIVATIVES OF THE STRAIGHT
CHAIN POLYHYDROXY ALCOHOLS WHICH CONTAIN 3 OR MORE CARBONS.

5. CLASSIFICATION OF MONOSACCHARIDES
MONOSACCHARIDES ARE DIVIDED INTO DIFFERENT GROUPS
ACCORDING TO:
•CHEMICAL NATURE OF THEIR CARBONYL GROUP
•NUMBER OF CARBON ATOMS

6. CLASSIFICATION OF MONOSACCHARIDES
BASED ON CHEMICAL NATURE OF THEIR CARBONYL GROUP
• ALDOSES
• KETOSES
BASED ON NUMBER OF CARBON ATOMS
• TRIOSES
• TETROSES
• PENTOSES
• HEXOSES

7. STRUCTURAL PROPERTIES
ISOMERISM
OPTICAL ACTIVITY
STEREOISOMERISM
MUTAROTATION
Ketose-Aldose Isomerism
D and L isomerism
Optical isomerism
Epimerism
Anomerism

8. ISOMERISM
D AND L ISOMERISM EPIMERISM
KETOSE-ALDOSE
ISOMERISM

9. CHEMICAL PROPERTIES
•ACTION OF STRONG ACIDS (FURFURAL FORMATION)
•ACTIONS OF ALKALIES (ENOLIZATION)
•OXIDATION (SUGAR ACID FORMATION)
•REDUCTION TO FORM SUGAR ALCOHOL
•ACTION OF PHENYL HYDRAZINE: OSAZONE FORMATION

10. BIOLOGICAL SUGAR DERIVATIVES
•PHOSPHORYLATED DERIVATIVES
•AMINO SUGARS
•DEOXY SUGAR
•SUGAR ACIDS
•SUGAR ALCOHOLS

11. DISACCHARIDES
IT CONSISTS OF TWO SIMILAR OR DISSIMILAR
MONOSACCHARIDES WHICH ARE LINKED BY A GLYCOSIDIC
BOND. MALTOSE, LACTOSE, AND SUCROSE ARE SOME
EXAMPLES.

12. MALTOSE
• IT CONTAINS TWO GLUCOSE
RESIDUES, JOINED BY GLYCOSIDIC
LINKAGE BETWEEN C-1 OF ONE
GLUCOSE AND C-4 OF OTHER,
LEAVING ONE FREE ANOMERIC
CARBON OF THE SECOND GLUCOSE
RESIDUE, WHICH ACTS AS A
REDUCING AGENT.

13. LACTOSE (MILK SUGAR)
IT IS PRESENT IN MILK. LACTOSE
CONTAINS ONE UNIT OF Β-D-GALACTOSE
AND ONE UNIT OF Β-D-GLUCOSE THAT
ARE LINKED BY Β GLYCOSIDIC LINKAGE.
IT IS A REDUCING DISACCHARIDE.
LACTOSE IS HYDROLYSED TO GLUCOSE
AND GALACTOSE BY LACTASE ENZYME IN
HUMANS.

14. ISOMALTOSE
IT CONSISTS OF TWO GLUCOSE
MOLECULES LINKED BY A GLYCOSIDIC
BOND. IT IS A DISACCHARIDE DERIVED
FROM DIGESTION OF STARCH OR
GLYCOGEN. IT IS HYDROLYSED TO
GLUCOSE IN THE INTESTINAL TRACT BY
AN ENZYME ISOMALTASE.

15. SUCROSE (COMMON TABLE SUGAR)
IT IS A DISACCHARIDE
FORMED OF GLUCOSE AND
FRUCTOSE. IT IS FORMED BY
PLANT. IT IS ALSO KNOWN AS
INVERT SUGAR.

16. OLIGOSACCHARIDES
THEY ARE CARBOHYDRATES BUILT BY LINKING OF MORE THAN
TWO MONOSACCHARIDE UNITS BY O-GLYCOSIDIC BONDS. E.G.
MALTOTRIOSE, RAFFINOSE, ETC.

17. POLYSACCHARIDES
THEY ARE ALSO CALLED GLYCANS, ARE POLYMERS OF LARGE
NUMBER OF MONOSACCHARIDES WHICH ARE LINKED TO EACH
OTHER BY GLYCOSIDIC BONDS. THEY ARE SPARINGLY SOLUBLE
IN WATER AND FORMS COLLOIDAL SOLUTION IN HOT WATER.
THEY NEITHER SWEET NOR HAVE REDUCING PROPERTIES.

18. CLASSIFICATION OF POLYSACCHARIDES
THEY ARE CLASSIFIED AS
• HOMOPOLYSACCHARIDES
THEY ARE ALSO CALLED HOMOGLYCANS, ARE POLYMERS OF THE
IDENTICAL MONOSACCHARIDES UNIT.
E.G. STARCH, GLYCOGEN AND CELLULOSE
• HETEROGLYCANS
THESE ARE POLYSACCHARIDES CONTAINING MORE THAN ONE
TYPE OF SUGAR RESIDUES. THEY ARE PRESENT IN CONNECTIVE
TISSUES.
EXAMPLE: - HEPARIN, HYALURONIC ACID, AGAR, GUM AND PECTIN

19. USES OF CARBOHYDRATES
• CARBOHYDRATES ARE THE MAIN SOURCES OF ENERGY IN THE BODY.
BRAIN CELLS AND RBCS ARE ALMOST WHOLLY DEPENDENT ON
CARBOHYDRATES AS THE ENERGY SOURCE. ENERGY PRODUCTION FROM
CARBOHYDRATES WILL BE 4 K CALORIES/G (16 K JOULES/G).
• STORAGE FORM OF ENERGY (STARCH AND GLYCOGEN).
• EXCESS CARBOHYDRATE IS CONVERTED TO FAT.
• GLYCOPROTEINS AND GLYCOLIPIDS ARE COMPONENTS OF CELL
MEMBRANES AND RECEPTORS.
• STRUCTURAL BASIS OF MANY ORGANISMS: CELLULOSE OF PLANTS;
EXOSKELETON OF INSECTS, CELL WALL OF MICROORGANISMS,
MUCOPOLYSACCHARIDES AS GROUND SUBSTANCE IN HIGHER
ORGANISMS.