#nursing #medical #biochemistry

1. Carbohydrate
Mr. Abhijit Bhoyar
Assistant Professor
Department of
Child Health Nursing
CLASSIFICATION
Part-I

2. Specific Learning Objectives
At the end of the lecture, the students will be
able to
• Classify carbohydrate.

3. Introduction
• Carbohydrates are often referred to as saccharides (Greek:
sakcharon–sugar).
• This categorization is based on the number of sugar units.
• Mono- and oligosaccharides are sweet to taste, crystalline in
character and soluble in water, hence they are commonly
known as sugars.
• They are broadly classified into three major groups.

4. Classification of
Carbohydrates
Monosaccharides
Oligosaccharides
Polysaccharides

5. Monosaccharides
• The word “Monosaccharides” derived from the Greek
word “Mono” means Single and “saccharide” means
sugar.
• Monosaccharides are the simplest group of
carbohydrates and are often referred to as simple
sugars.
• Monosaccharides are polyhydroxy aldehydes or ketones
which cannot be further hydrolysed to simple sugar.

6. Cont….
• They have the general formula Cn(H2O)n.
• They are sweet in taste , soluble in water and
crystalline in nature.
• They contain 3 to 10 carbon atoms, 2 or more hydroxyl
(OH) groups and one aldehyde (CHO) or one ketone
(CO) group.
• The monosaccharides are divided into different
categories, based on the functional group and the
number of carbon atoms

7. Properties of Monosaccharides
1. Colour - colorless
2. Shape - crystalline
3. Solubility – water soluble
4. Taste - sweet
5. Optical activity – Optically active.
(a) Dextrorotatory (‘d’ form) and
(b) Levorotatory (‘l’ form).

8. Dextrorotatory (‘d’ form) and (b) Levorotatory
(‘l’ form).
If a compound rotates plane polarized
light in the clockwise (+) direction, it is said to be
dextrorotatory, while if it rotates light in the
counterclockwise (-) direction it is levorotatory.

9. Cont.….
6) Mutarotation – ( a gradual change in the optical
rotation of freshly prepared solutions of reducing
sugars)

10. Cont….
• Glucoside formation - Glucose + Methyl alcohol =
Methyl glucoside
• Esterification- It is a chemical reaction that takes
place during the formation of the ester. Esterification
is the chemical process that combines alcohol (ROH)
and an organic acid (RCOOH) to form an ester
(RCOOR) and water.

11. Cont….
• Reducing agents – (a substance that reduces a
chemical compound usually by donating
electrons.) Monosaccharides reduce oxidizing agent
such as hydrogen peroxide. In such reaction, sugar
is oxidized at the carbonyl group and oxidizing
agent becomes reduced.
• Formation of Osazone- A yellow crystalline
compound formed by the action of phenyl-
hydrazine on a sugar in the presence of acetic acid.

12. Classification of Monosaccharides
Monosaccharides are classified in two ways
1. Based on the number of carbon atoms present in
them
2. Based on the presence of carbonyl group.

13. Based on the number of carbon atoms
present in them
• The naturally occurring monosaccharides contain
three to seven carbon atoms per molecule.
• Monosaccharides of specific sizes may be indicated by
names composed of a stem denoting the number of
carbon atoms and the suffix -ose.
For example, the terms triose, tetrose, pentose, and
hexose signify monosaccharides with, respectively,
three, four, five, and six carbon atoms.

14. Cont….
Based on the number of carbon atoms,
the monosaccharides are regarded as
1. Trioses (3C)
2. Tetroses (4C)
3. Pentoses (5C)
4. Hexoses (6C)
5. Heptoses (7C)

15. Based on the presence of carbonyl group
Monosaccharides are also classified
as
Based on the presence
of carbonyl group
Aldoses Ketoses

16. Cont….
• Aldoses : Those monosaccharides that contain an
aldehyde functional group are called aldoses.
e.g. Glyceraldehyde, Glucose.
• Ketoses : Those monosaccharides containing a ketone
functional group on the second carbon atom are referred
to as ketoses.
e.g. Dihydroxyacetone, Fructose.

17. Cont….
• Combining these classification systems gives general
names that indicate both the type of carbonyl group
and the number of carbon atoms in a molecule.
• Thus, monosaccharides are described as
aldotetroses, aldopentoses, ketopentoses,
ketoheptoses.
• Glucose and fructose are specific examples of an
aldohexose and a ketohexose, respectively.

18. Classification of monosaccharides with selected
examples
Monosaccharides
(empirical formula)
Aldose Ketose
Trioses (C3H6O3) Glyceraldehyde Dihydroxya
cetone
Tetroses (C4H8O4) Erythrose Erythrulose
Pentoses (C5H10O5) Ribose Ribulose
Hexoses (C6H12O6) Glucose Fructose
Heptoses (C7H14O7) Glucoheptose Sedoheptul
ose

19. Trioses
• Trioses are “Monosaccharides” containing 3 carbon
atoms.
• The molecular formula of triose is C3H6O3.
Characteristics
• Trioses are simple sugars and soluble in water.
• They are sweet in taste.
• The triose may contain an aldehyde group (aldotriose)
or a ketone group. (ketotriose).
• Example- Glycerose and Dehydroxyacetone

20. Tetroses
• Tetroses are “Monosaccharides” containing 4 carbon
atoms.
• The molecular formula of tetrose is C4H8O4.
Characteristics
• Tetroses are simple sugars and soluble in water.
• They are sweet in taste and crystalline forms.
• The tetroses may contain an aldehyde group (
(ketotetrose).

21. Pentoses
• Pentoses are “Monosaccharides” containing 5 carbon
atoms.
• It is an important component of “nucleic acid”.
• The molecular formula of Pentose is C5H10O5

22. Characteristics of Pentoses
• Pentoses are simple sugars.
• Pentoses are soluble in water.
• They are sweet in taste.
• They are crystalline forms.
• The pentoses may contain an aldehyde group
(aldopentose) or a ketone group (ketopentose).

23. Hexoses
• Hexoses are “Monosaccharides” containing 6 carbon
atoms.
• The molecular formula of Hexose is C6H12O6.
Characteristics
• Hexoses are simple sugars and soluble in water.
• They are sweet in taste.
• They are crystalline forms.
• The pentoses may contain an aldehyde group
(aldohexose (ketohexose)

24. Oligosaccharides
• Oligosaccharides (Greek: oligo-few) contain
• 2-10 monosaccharide molecules which are liberated
on hydrolysis.
• Based on the number of monosaccharide units
present, the oligosaccharides are further subdivided
to
• disaccharides, trisaccharides etc.

25. Types of Oligosaccharides
Disaccharides Trisaccharides
Tetrasaccharides

26. Disaccharides
• Disaccharides are the most common among the
oligosaccharides.
• Disaccharide consists of two monosaccharide units
(similar or dissimilar) held together by a glycosidic
bond.

27. Cont…
• They are crystalline, water-soluble and sweet to
taste.
• The most abundant disaccharides are sucrose, lactose
and maltose.
• Other disaccharides include isomaltose, cellobiose
and trehalose

28. Types Of Disaccharides
The disaccharides are of two
types
1. Reducing disaccharides with free aldehyde
or keto group e.g. maltose, lactose.
2. Non-reducing disaccharides with no free
aldehyde or keto group e.g. sucrose,
trehalose.

29. Maltose
• Maltose which is also known as malt is a disaccharide
made up of two alpha D glucose unit.
• The two-unit of glucose are linked with an alpha 1,4
glycosidic bond.
• In the small intestinal lining in humans, the enzyme
maltase and isomaltase break down the molecules
of maltose into two glucose molecule, which is then
absorbed by the body.
• Maltose = 2 molecules of glucose

30. Sucrose
• Sucrose (cane sugar) is the sugar, mostly produced by
sugar cane and sugar beets.
• Sucrose is made up of α -D-glucose and β- D-
fructose.
• The two monosaccharides are held together by a
glycosidic bond (D1 o E2), between C1 of D-
glucose and C2 of E-fructose.
• The reducing groups of glucose and fructose are
involved in glycosidic bond, hence sucrose is a
non-reducing sugar, and it cannot form osazones.

31. Cont….
• Sucrose is an important source of dietary carbohydrate.
• It is sweeter than most other common sugars (except
fructose) namely glucose, lactose and maltose.
• Sucrose is employed as a sweetening agent in food
industry.
• The intestinal enzyme—sucrase—hydrolyses sucrose to
glucose and fructose which are absorbed.
• 1 mol. of glucose + 1 mol. Of fructose

32. Lactose
• Lactose is more commonly known as milk sugar
since it is the disaccharide found in milk.
• Lactose is composed of β -D-galactose and β –D
glucose held together by β (1 4) glycosidic bond.
• 1 mol. Of glucose + 1 mol. Of galactose

33. Trisaccharides
• It composed of three
monosaccharide.
Ex: Raffinose (Formed by
one mole of each i.e.
glucose, fructose,
galactose). It is presnt in
molasses

34. Tetrasaccharides
• It Composed of four monosaccharide .
Ex: Stachyose- (composed of two moles of galactose
one mole of glucose & one mole of fructose).
It is present in onion.

35. Summary
So far we have discussed about
classification of carbohydrate.

36. Expected Questions
Essay/Situational Type
• Define carbohydrate and classify it in detail.

37. References
1. Jacob Anthikad, Biochemistry for nurses 3rd ed.
2. Pankaja Naik, Essentials of Biochemistry, 1st ed.
3. Satyanarayan, Essentials of Biochemistry, 2nd ed.
4. A. C. Deb, Biochemistry, 4th ed.

38. THANK YOU