1. Dr. Basima Sadiq Ahmed PhD. Clinical biochemist
CARBOHYDRATES
Dr. Basima Sadiq Ahmed
PhD. Clinical biochemist

2. CARBOHYDRATES   Define as aldehydic or ketonic derivetives of poly hydroxy alcohols and their polymers having hemiacetal glycosidic linkages. .

3. MEDICAL AND BIOLOGICAL IMPORTANCE
major source of energy for man. e.g, glucose is used in the human body for energy production.
serve as reserve food material in humans and in plants. For example, glycogen in animal tissue and starch in plants serves as reserve food materials.
Carbohydrates are components of several animal structure and plant structures. are components of skin, connective tissue, tendons, cartilage and bone. In plants, cellulose is a component of wood and fiber.
Some carbohydrates are components of cell membrane and nervous tissue.
Carbohydrates are components of nucleic acids and blood group substances.
Carbohydrates are involved in cell-cell interaction.
Aminosugars, derivatives of carbohydrates are components of antibiotics like erythromycin,streptomycine is a glycoside and carbomycin.
Ascorbic acid, a derivative of carbohydrate is a water-soluble vitamin.
Bacterial invasion involves hydrolysis of mucopolysaccharides.

4. .
Carbohydrates are classified into three major classes based on number of carbon chains
They are:
1. Monosaccharides
2. Oligosaccharides
3. Polysaccharides
Functions;
1-provide energy.
2-as structural components of membranes.
3-as structural basis for DNA and RNA,nucleosides and nncleotides.
4-as source of carbone skeltones for some amino acids.

6. Monosaccharides are carbohydrates with: The simplest carbohydrates
Monosaccharides (Simple Sugar)
A carbohydrate that cannot be split or hydrolyzed into smaller carbohydrates.
Monosaccharides are carbohydrates with:
The simplest carbohydrates
3-9 carbon atoms
A carbonyl group (aldehyde or ketone)
Several hydroxyl groups
Cn(H2O)n
CnH2nOn ║
C ─ H │
H─ C ─ OH
CH2OH O

7. The simplest aldose is glyceraldehyde.
Monosaccharides (Simple Sugar)
The simplest aldose is glyceraldehyde.
The simplest ketose is dihydroxyacetone.
C3H6O3
C3H6O3
Constitutional Isomers

8. (C6H12O6, aldohexose) – Blood sugar The most abundant monosaccharide
Some important Monosaccharides
Glucose (Dextrose)
(C6H12O6, aldohexose) – Blood sugar
The most abundant monosaccharide
Is found in fruits, vegetables,
corn syrup, and honey.
Is found in disaccharides such as sucrose, lactose, and maltose.
Makes up polysaccharides such as starch, cellulose, and glycogen.

9. - Normal blood glucose levels are 70-110 mg/dL.
Some important Monosaccharides
Glucose (Dextrose)
- Normal blood glucose levels are mg/dL.
- Excess glucose is stored as the polysaccharide glycogen or as fat.
- Insulin (a protein produced in the pancreas) regulates blood glucose levels by stimulating the uptake of glucose into tissues or the formation of glycogen.
- Patients with diabetes produce insufficient insulin to adequately regulate blood sugar levels, so they must monitor their diet and/or inject insulin daily.

10. Is the sweetest of the carbohydrates.
Some important Monosaccharides
Fructose
(C6H12O6, ketohexose),
Is the sweetest of the carbohydrates.
Is found in fruit juices and honey (fruit sugar).
In bloodstream, it is converted to its isomer, glucose.
Is bonded to glucose in sucrose (a disaccharide known as table sugar).

12. Has a similar structure to glucose except for the –OH on Carbon 4.
Some important Monosaccharides
Galactose
(C6H12O6, aldohexose),
Has a similar structure to glucose except for the –OH on Carbon 4.
Cannot find in the free form in nature.
Exist in the cellular membranes of the brain and nervous system.
Combines with glucose in lactose (a disaccharide and a sugar in milk).

13. Disease - Galactosemia
missing the enzyme that convert galactose to glucose.
Accumulation of galactose in the blood and tissues.
Mental retardation and cataract

14. . PROPERTIES OF MONOSACCHARIDES 1. Optical Isomerism
All the monosaccharides except dihydroxyacetone contain at least one asymmetric carbon atom and hence they exhibit optical isomerism. The two optical isomers of glyceraldehyde containing one asymmetric carbon atom are D-glyceraldehyde an L-glyceraldehyde. The optical isomers are also called as enantiomers. sugars present in the body are all D-isomers

15. 1. Carbon with four different groups bonded to it.
Fischer Projections
1. Carbon with four different groups bonded to it.
2. The chiral carbon furthest from the carbonyl group (-CHO). * * * * * * * * HO H
D - glucose
L - glucose
Naturally occurring enantiomer

16. 2. Optical Activity
Monosaccharides except dihydroxy acetone exhibit optical activity because of the presence of asymmetric carbon atom. If a sugar rotates plane polarized light to right then it is called as dextrorotatory and if a sugar rotates the plane polarized light to the left then it is called as levorotatory. Usually ‘+’ sign or ‘D’ indicates dextrorotation and ‘–’ sign or L indicates levorotation of a sugar. For example, D-glucose which is dextrorotatory is designated as D(+)
glucose and D-fructose which is levorotatory is designated as D(–) fructose. .

17. 3. Epimers
Are those monosaccharides that differ in the configuration of –OH group on 2nd, 3rd and
4th carbon atoms. Epimers are also called as diastereoisomers. Glucose, galactose and mannose. Galactose is an epimer of glucose because, configuration of hydroxyl group on 4th carbon atom Similarly, mannose is an epimer of glucose because configuration of hydroxyl group on 2n .

19. .
4. Functional Isomeris
Functional isomers have same molecular formulae but differ in their functional groups.
5. Ring Structures
In solution, the functional aldehyde group of glucose combines with hydroxyl group of 5th
carbon atom. As a result a 6 numbered heterocyclic pyranose ring structure containing
5 carbons and one oxygen is formed.The linkage between aldehyde group and
alcohol is called as ‘hemiacetal’ linkage. Similarly, a 5 numbered furanose ring structure is
formed from fructose when keto group combines with hydroxyl group on 5 carbon atom. The
linkage between keto and alcohol group is called ‘hemi ketal’ linkage. (Fig. 5.5). Both hemi
acetal and hemi ketal are internal or intra molecular linkages

21. Aldehydes and ketones react with alcohols to form hemiacetals.
Cyclic Structure – Haworth Structure
Aldehydes and ketones react with alcohols to form hemiacetals.
Unstable
A hemiacetal contains a hydroxyl group (OH) and an alkoxy group (OR)
on the same carbon.

22. Cyclic Structure – Haworth Structure

23. .

24. 6. Anomers
Those monosaccharides that differ in configuration of OH groups on carbonyl carbon or
anomeric carbon are called as anomers. Formation of ring structure of glucose generates
anomers of glucose, which are designated as ∞ and β forms. These two forms of glucose differ
in the configuration of OH on carbonyl carbon or 1st carbon atom. In the ∞ -form the
hydroxyl group on anomeric carbon (1st carbon) atom points to the right where as in the
β-form to the left (Fig. 5.6). .

25. Alpha (α) Beta () Cyclic Structure – Haworth Structure1 1
Anomeric carbon 1 1 1
Alpha (α)
Beta ()
More stable form
Anomers

26. Cyclic Structure – Haworth Structure1
Anomeric carbon OH
C=O 5 2
CH2OH OH H HO
HOCH2
-D-fructose -D-fructose 2

28. .
7. Mutarotation
Monosaccharides containing asymmetric carbon atom rotate plane polarized light.
The change in optical rotation when either form of glucose is allowed to stand in solution is called mutarotation.It is due to conversion of cyclic form of glucose to straight chain form.

29. Important monosaccharides in the metabolic point of view are glucose, fructose, galactose,
ribose, erythrose and glyceraldehyde Commonly glucose is referred as dextrose. All monosaccharides containing free aldehyde or keto group reduces ions like Cu2+ under alkaline conditions.

30. . Biologically Important Sugar (Glucose) Derivatives
Sugar derivatives of biological importance are sugar acids, sugar alcohols, deoxy sugars,
sugar phosphates, amino sugars and glycosides.
1. Sugar acids
Oxidation of aldo group of sugars produces aldonic acids. For example, oxidation of glucose
produces gluconic and oxidation of terminal alcohol group (–OH sixth carbon atom)
of glucose produces glucuronic acid or uronic acid (Fig. 5.8). Uronic acids are components
of mucopolysaccharides and required for detoxification.
2. Sugar alcohols
Reduction of aldose and keto groups of sugar produces polyhydroxy alcohols or polyols.
These polyols are intermediates of metabolic reactions. Other sugar alcohols are glycerol
and inositol. The alcohols formed from glucose, galactose and fructose are sorbitol, galactitol
and sorbitol, respectively. .

31. .
3. Deoxy sugars
Those sugars in which oxygen of a hydroxyl group is removed leaving hydrogen. Deoxyribose
is an example (Fig. 5.9). It is present in nucleic acids. Fucose is another deoxy sugar present
in blood group substances.

33. 4. Sugar phosphates
Breakdown of sugar in animals involves formation of sugar phosphates. Glucose-6-phosphate
is an example for a sugar phosphate (Fig. 5.9).
5. Aminosugars
Those sugars in which an amino group is substituted for a hydroxyl group. D-glucosamine
is an example for an amino sugar (Fig. 5.9). Amino sugars are components of
mucopolysaccharides, and antibiotics.
6. Glycosides
Are of two types:
(a) O-glycosides. When hydroxyl group on anomeric carbon of a sugar reacts with an
alcohol (sugar) O-glycoside is formed (Fig. 5.10). O-glycosidic linkage is present in
disaccharides and polysaccharides. So, disaccharides, oligosaccharides and polysaccharides
are O-glycosides.
(b) N-glycosides. N-Glycoside is formed when hydroxyl group on anomeric carbon of sugar
reacts with an amine (Fig. 5.10). N-glycosidic linkage is present in nucleotides, RNA and
DNA. So, nucleotides, RNA and DNA are examples for N-glycosides .

35. OLIGOSACCHARIDES
They consist of 2-10 monosaccharide units. The monosaccharides are joined together by
glycoside bonds. Most important oligosaccharides are disaccharides.
Disaccharides
They provide energy to human body. They consist of two monosaccharide units held together
by glycosidic bond. So, they are glycosides. Most common disaccharides are maltose, lactose
and sucrose (Fig. 5.11).

37. Maltose
Structure
It contains two glucose units. The anomeric carbon atom of first glucose and carbon atom
4 of the second glucose are involved in glycosidic linkage. The glycosidic linkage of maltose
is symbolized as ∞-(1→4).
Systematic name for maltose is (1→4)-∞-D glucopyranose.
Maltose is a reducing sugar because anomeric carbon of second glucose is free.. It may be formed during the hydrolysis of starch.
Lactose
It contains one glucose and one galactose. The anomeric carbon atom of galactose and
carbon atom 4 of glucose are involved in glycosidic linkage. It is symbolized as β (1→4). The
systematic name for lactose is (1→4)-β-D-glucopyranose. Lactose is areducing sugar because anomeric carbon of glucose is free.Lactose is synthesized in mammary gland

38. Sucrose
It contains glucose and fructose. The anomeric carbon of glucose and anomeric carbon of
fructose are involved in glycosidic linkage. Further, glucose is in ∞-form whereas fructose
is in β-form in sucrose. Hence the glycosidic linkage of sucrose is designated as ∞, β(1→2).
Its systematic name is (1→2)-β-D-fructofuranose. Sucrose is a non reducing sugar because both the functional groups of glucose and fructose are involved inglycosidic linkage.
.Invert sugar
Sucrose has specific optical rotation of +66.5°. On hydrolysis, it changes to –19.8°. This
change in optical rotation from dextro to levo when sucrose is hydrolysed is called as
inversion. The hydrolysis mixture containing glucose and fructose is called as invert sugar.
The change in optical rotation on hydrolysis is because of fructose which is more levo
rotatory than dextro rotatory glucose.

39. POLYSACCHARIDES
They are polymers of monosaccharides. They contain more than ten monosaccharide units.
The monosaccharides are joined together by glycosidic linkage.
Classification of Polysaccharides
Polysaccharides are classified on the basis of the type of monosaccharide present. The two
classes of polysaccharides are homo-polysaccharides and hetero-polysaccharides.
(a) Homopolysaccharides. They are entirely made up of one type of monosaccharides. On
hydrolysis, they yield only one kind of monosaccharide.
(b) Heteropolysaccharides. They are made up of more than one type of monosaccharides.
On hydrolysis they yield more than one type of monosaccharides.
Homopolysaccharides
Important homopoly-saccharides are starch, glycogen, cellulose, dextran and inulin and
chitin. All these contain glucose as repeating unit. Other name for homopolysaccharides are
homoglycans.

40. Starch
Structure
1. It consist of two parts. A minor amylose component and a major amylopectin component.
2. Amylose is a straight-chain polymer of glucose units. (1→4) glycosidic linkage is present
between glucose units.
3. In contrast amylopectin is a branched molecule (Fig. 5.12). In the linear portion of
amylopectin (1→4) glycosidic linkage exist between glucose units whereas (1→6) glycosidic
linkage exist at branch points between glucose residues. The branching occurs in
amylopectin for every 2-30 glucose units.
4. Amylose has helical coiled secondary structure and usually 6 glucose residue make one
turn (Fig. 5.12). Because of branching secondary structure of amylopectin is a random
coil structure.

42. Glycogen
Structure
1. The structure of glycogen is similar to that of amylopectin of starch. However, the
number of branches in glycogen molecule is much more than amylopectin (Fig. 5.13).
2. There is one branch point for 6-7 glucose residues

44. Cellulose
Structure
1. It has linear chain of glucose residues, which are linked by β(1→4) glycosidic linkage
(Fig. 5.14

45. . 2. It occurs as bundle of fibres in nature.
3. The linear chains are arranged side by side and hydrogen bonding between adjacent
stands stabilizes the structure.
Dextran
Structure
1. It has structure similar to amylopectin.
2. In the linear part, glucose units are linked by ∞(1→6) glycosidic bond and ∞(1→3)
glycosidic linkage is present between glucose unit at branch points. 
Inulin
It is a polysaccharide composed of fructose. β(1→2) glycosidic linkage is present
between fructose units 
Chitin
. A polysaccharide composed of N-acetyl glucosamine. Glycosidic linkage is
β(1→4). .

46. HETEROPOLYSACCHARIDES
They are also called as mucopolysaccharides and glycosaminoglycans. Mucopolysaccharides
consist of repeating disaccharide units. The disaccharide consist of two types monosaccharides.
The mucopolysaccharides combines with proteins like collagen and elastin and forms
extracellular medium or ground substance of connective tissue. Mucopolysaccharides are
also components of extracellular matrix of bone, cartilage and tendons. The complex of
mucopolysaccharide and protein is called as proteoglycan.
Few important mucopolysaccharides or glycosaminoglycans (GAGs) are:
Hyaluronic Acid (HA)
Structure
The repeating disaccharide of hyaluronic acid consist of glucuronic acid and Nacetylglucosamine.

47. Functions
1. It is present in synovial fluid and function as lubricant.
2. It is also present in skin, loose connective tissue, umbilical cord and ovum.
3. It is present in vitreous body of eye.
Medical importance
1. As the age advances hyaluronic acid is replaced by-dermatan sulfate in synovial fluid.
Dermatan sulfate is not a good lubricant, hence age related pains develop in old people.
2. In young people, vitreous is clear elastic gel in which hyaluronic acid is associated with
collagen. As the age advances the elasticity of vitreous is reduced due to decreased association
between collagen and hyaluronic acid. As a result, vision is affected in older people.
Chondroitin sulfate A and B chondroitin-4-sulfate and chondroitin-6-sulfate
Structure
1. The repeating disaccharide unit of chondroitin sulfates consist of glucuronic acid and
N-acetyl galactosamine. N-acetyl galactosamine is sulfated.
2. In chondroitin-4-sulfate, 4th carbon atom of N-acetyl galactosamine is sulfated where as
in chondroitin-6-sulfate the 6th carbon is sulfated

48. 1. Chondroitin sulfates are components of cartilage, bone and tendons.
2. They are also present in the cornea and retina of the eye.
3. Chondroitin sulfate content decreases in cartilage as age advances.
Heparin
Structure
1. The repeating disaccharide unit of heparin consist of glucosamine and either iduronic
acid or glucuronic acid. Majority of uronic acids are iduronic acids. Further amino groups of glucosamine is
sulfated. .

49. . Functions 1. Heparin is a normal anti-coagulant present blood.
2. It is produced by mast cells present in the arteries, liver, lung and skin. heparin is an intracellular component.
Dermatan Sulfate
Structure
The repeating disaccharide consist of Iduronic acid and N-acetyl galactosamine sulfate.

50. . Functions 1. It is present in skin, cornea and bone.
2. It has a role in corneal transparency maintenance.
Keratan sulfates I and II
Structure
1. The repeating disaccharide consist of galactose and N-acetyl glucosamine sulfate.
2. Type I and II have different attachments to protein.

51. Functions
1. They are components of cartilage, cornea and loose connective tissue. Keratan sulfate l is important for corneal transparency. 
GLYCOPROTEINS
These oligosaccharide chains are attached to proteins by O-glycosidic and N-glycosidic bonds.
Further oligosaccharide is composed of fucose, N-acetyl glucosamine, galactose and glucose.
The oligosaccharide chains have important functions like:
1. Oligosaccharide present on the surface of erythrocytes are responsible for the classification
of blood groups. They determine blood group and hence they are called as blood group
substances.
2. Oligosaccharides determine the life span of proteins.
3. Cell-cell recognition depends on oligosaccharide chains of glycoproteins.
4. Glycoproteins of some invertebrates function as antifreezing agents. They are known as
antifreeze glycoproteins (AFGPs). .

52. . Sialic Acids Structure
1. Sialic acids are acyl derivatives of neuraminic acid.
2. Neuraminic acid is a 9 carbon sugar consisting of mannosamine and pyruvate. Usually
amino group of mannosamine of neuraminic acid is acetylated (NANA).
Functions;
1. Oligosaccharides of some membrane glycoproteins contains a terminal sialic acid.
2. Sialic acid is an important constituent of glycolipids present in cell membrane and
nervous tissue. .