isomerism, pentoses, reactions of carbohydrates, hexoses

1. Biochemistry
Lec 4-10
Maria Gul
Lecturer
Jips,Lahore

2. Epimers
• Epimers: Isomers differing as a result of variations in configuration of
the —OH and —H on carbon atoms 2, 3, and 4 of glucose are known
as Epimers. Biologically,
• Epimers of glucose are mannose (epimerized at carbon
• 2) and galactose (epimerized at carbon 4) (Figure 14–5).

3. anomeric carbon.
• Generally, hemiacetal formation occurs when the
nucleophilic hydroxyl group of an alcohol attacks the
carbonyl carbon of an aldehyde functional group. In
the case of glucose specifically, this reaction occurs
intramolecularly between the hydroxyl group of
Carbon-5 and the aldehyde carbon resulting in the
formation of a more stable, six-membered ring. In the
process, a new chiral center is formed at the former
carbonyl carbon, which is now called the anomeric
carbon.

4. Cyclic structure or ring structure of
monosaccharides
• Hemiacetal (aldehyde and alcohol)
• Hemiketal (Ketone and alcohol)

5. Anomers
• These are two isomers which differ in configuration around the
anomeric carbon atom, the carbon atom of carbonyl group which is
carbon no 1 in aldoses and carbon 2 in ketoses.
• α and β D-glucose

6. Amylene oxide structure and butylene oxide
structure

7. Biochemistry
• Lecture 5
• Maria Gul
• lecturer

8. Pyranose and furanose isomerism
• Pyranose and furanose ring structures: The ring
• structures of monosaccharides are similar to the ring
structures of either pyran (a six-membered ring) or
furan (a five membered ring) For glucose in solution,
more than 99% is in the pyranose form.

11. Alpha and beta anomers
• Alpha and beta anomers: The ring structure of an aldose is
a hemiacetal, since it is formed by combination of an
aldehyde and an alcohol group. Similarly, the ring structure
of a ketose is a hemiketal. Crystalline glucose is α-d
glucopyranose. The cyclic structure is retained in solution,
but isomerism occurs about position 1, the carbonyl or
anomeric carbon atom, to give a mixture of α
glucopyranose (38%) and β-glucopyranose (62%). Less than
0.3% is represented by α and β anomers of glucofuranose.

13. Chair and boat

14. Biochemistry
• Lecture 6
• Maria Gul
• Lecturer

15. Optical isomerism in monosaccharides
• Optical isomers
• Rotation of plane polarized light is measured by polarimetry or
polariscope
• A beam of light is passed is passed through Nicol prism (cut crystals of
calcite or transparent caco3) which act as polarizer converts into
plane polarized light. This beam of light is passed through the a
solution chemical substances contain in glass tube of known length.
A second Nicol prism acts as analyzer. It can be rotated to find out the
degree of rotation

16. Formula
• Specific rotation in degree of 1 gram of the substance /mL of the
solvents in one decimeter (10 cm) in length.

17. Reaction of carbohydrates
• Chemical properties depend upon the presence of various groups in
monosaccharides aldehyde, ketone, hydroxyl groups
• Rx with Hydrazine to form Osazone
Phenylosazone is produce As a result of sugar solution with phenyl
hydrazine

18. Types of Crystals
Sugar name Osazone name Crystal type
Glucose, fructose, Mannose ,
galactose
glucosazone Needle shape
Lactose Lactosazone crystals Cluster of fine needles
maltose Maltosazone: Star shaped

20. Oxidation to produce sugar acid
• Oxidation at mild condition with bromine water Glucanic acid
COOH # 1
• Glucuronic acid COOH # 6
• Glucaric acid oxidation with HNO3 COOH # 1, 6.

21. Reducing action of sugars in alkaline solution
• All the sugar containing the potential at aldehyde and ketone group
that have free anomeric carbon are oxidized at alkaline PH by oxygen
and oxidizing agents . This means that they act as reducing agents.
They can easily reduce oxidizing agents AG+, HG2+,BI2+, CU2+.
• Sugars are oxidize to sugar acid
• Benedicts and barfoed reagents are used to determine the reducing
sugars
• Non reducing sugar is sucrose .

22. • Sodium potassium tartarate (Rochelle salt) and strong alkali
NaOH/KOH as in Fehling’s solution
• • Sodium citrate and weak alkali sodium carbonate as in Benedict’s
Qualitative reagent

23. biochemistry
• Lecture 7
• Maria Gul
• lecturer

24. Action with Acids
• Strong acids remove water from hexose converting hexoses to furfural
or colored compounds . This reaction is basis of molisch test for
carbohydrates (alpha naphthol).

27. Action with bases
• Dilute basic solution at a low temperature can bring about a
rearrangement of groups around anomeric carbon atom and its
adjacent carbon atom. Glucose can be changed to fructose and
mannose.

28. Reduction of sugars

30. Biochemistry
• Lecture 8
• Maria Gul
• lecturer

34. Pentose's

37. Biochemistry
• Lecture 9
• Maria Gul
• lecturer

38. Essential Nutrients
Fuels
• Carbohydrates
• Fats
• Proteins
Required Components
• Essential amino acids
• Essential fatty acids
• Vitamins
• Minerals
• Water

40. Fuel Metabolism. We obtain our fuel primarily from
carbohydrates, fats, and
proteins in our diet
• Fuel Stores.
• Fuel Requirements

44. Biochemistry
• Lecture 10
• Maria Gul
• lecturer