Carbohydrates are polyhydroxy aldehydes or ketones or compounds derived from their hydrolysis. includes- Definition, classification, examples, enantiomers, epimers, anomers, D and L isomers, ozasone testing, reducing and non reducing sugars, chemical tests and disease.

1. CARBOHYDRATES
By: Payal Desai Naik
1

2. DEFINITION
• Carbohydrates are polyhydroxy aldehydes or ketones or compounds derived
from their hydrolysis.
• Carbohydrates are also known as sugars.
• The general formula of carbohydrate is Cn(H2O)n.
• Carbohydrates are mainly composed of carbon, hydrogen and oxygen.
• The term “sugar” is applied to carbohydrates soluble in water and sweet to taste.
2

3. FUNCTIONS OF CARBOHYDRATES
1. Most abundant dietary source of energy in all organisms.
2. They are precursors for many organic compounds (fats,
amino acids).
3. Carbohydrates (glycoproteins and glycolipids) participate in
structure of cell membrane and cellular functions.
4. Carbohydrates serve as storage form of energy to meet
energy demands of body.
5. They are structural components of many organisms ( e.g. cell
wall of microorganisms)
3

4. CLASSIFICATION OF CARBOHYDRATES
4

5. EXPLANATION OF CLASSIFICATION
1. Monosaccharaides
• They contain single polyhydroxy aldehyde or ketone unit.
• These carbohydrates cannot be hydrolyzed into simpler compounds.
I. They are further classified based on functional group
a) Aldoses
When the functional group in a monosaccharide is an aldehyde ( -HC=O) they are
known as aldoses
Example: glucose, glyceraldehyde.
b) Ketoses
When the functional group in monosaccharide is keto group ( -C=O) they are
known as ketoses
Example: fructose
Keto functional
group
5

6. II. They are further classified based on number of carbon atoms.
a) Trioses: contain 3 carbon atoms (example: glyceraldehyde)
b) Tetroses: contain 4 carbon atoms (example- erythrose)
c) Pentoses: contain 5 carbon atoms (example- ribose, xylose)
d) Hexoses: contain 6 carbon atoms ( example- glucose, fructose)
e) Heptoses: contain 7 carbon atoms (example- glucoheptose)
glyceraldehyde Erythrose Ribose Fructose Glucoheptose
6

7. 2. Disaccharides
Consists of 2 monosaccharaides units linked together by covalent bond.
They give two monomeric units on hydrolyses.
Example: maltose, sucrose, lactose
3. Oligosaccharides
Contain 2-10 monosaccharide units.
Give 2-10 monomeric units on hydrolysis.
Example: raffinose
7
(maltose) -1 ----4 glysosidic linkageɑ

8. 4. Polysaccharides
• Contain very long chain of hundreds and thousands of monosaccharide units.
• They can be straight or branched.
• They are made of 1 or different types of sugar.
• All monomeric units are linked together by glycosidic linkage.
• They are carbohydrates of higher molecular weight.
• Mostly insoluble in water.
They are further classified into 2
a) Homopolysaccharides:
These are polysaccharides made up of only one type of monosaccharide.
On hydrolysis they give only one type of monosaccharide.
Example : starch, cellulose, glycogen.
b) Heteropolysaccharides:
These are polysaccharides made up of more than one type of monosaccharide.
On hydrolysis they give two or many types of monomers.
Example: heparin, hyaluronic acid
8

9. 9
Homopolysaccharide- starch
Heteropolysaccharide- heparin

10. MONOSACCHARIDES- STRUCTURAL FEATURES
1. Stereoisomerism
• It is an important character of monosaccharides.
• Stereoisomers are the compounds that have the same structural formulae
but differ in their spatial configuration. (three dimension structure)
Asymmetric carbon
• A carbon is said to be asymmetric (chiral) when it is attached to four
different atoms or groups.
• A carbon atom is said to be asymmetric when its mirror images are non-
superimposable on each other
10

11. Epimers
•If two monosaccharaides differ from each other in their configuration around
single specific carbon atom, they are known as epimers of each other.
•Glucose and mannose are epimers of each other as they differ in configuration at
C-2 i.e –H and –OH are on opposite side in both.
•Glucose and galactose are epimers as they differ in configuration at C4 carbon.
•The process of interconversion of epimers (i.e from glucose to galactose) is
known as epimerization and takes place in presence of epimerases enzyme.
11**Image taken from google search engine

12. Enantiomers
•They are chiral molecules.
•Enantiomers are stereoisomers that are mirror images of each other.
•Non-superimposible mirror images.
•Enantiomeric pair have identical physical property.
•Enantiomers are optically active. (they differ in arrangement at the carbon atom
just above terminal carbon/alcohol.)
12
**Image taken from google search engine

13.  D AND L- ISOMERS
• D and L-isomers are mirror images of each other .
• They differ in the spatial arrangement of –H and –OH groups on carbon atom.
• The carbon adjacent to terminal primary alcohol determines weather the sugar is
D or L- isomer.
• If the –OH group on the bottom-most asymmetric carbon is on the right side, the
notation is D
• If the –OH group on the bottom-most asymmetric carbon is on the left side, the
notation is L
• In case of glucose we consider C5 carbon and in case of glyceraldehyde C2.
Note: Naturally occurring monosaccharides in mammalian tissues are mostly of D-
configuration as the enzyme mechanism in the body is specific to metabolize D-
series of monosaccharides.
13

14.  Optical activity of sugars
• The compounds that have tendency to rotate the plane polarized light are called
optically active.
• Optical activity is characteristic feature of compounds with asymmetric carbon
atom.
• When a beam if polarized light is passed through the solution of an optical
isomer, it will rotate the light to left or right.
• The optical rotation is measured by an instrument called polarimeter.
a) Dextrorotatory (D)
• The compounds that rotate the plane polarized light to right side.
• They are denoted by (+) sign.
b) Levorotatory (L)
• The compounds that rotate the plane polarized light to left side or left.
• They are denoted by (-) sign.
c) Racemic mixture
• If D and L isomers are present in equal concentration, it is known as racemic
mixture or DL mixture.
• They do not exhibit any optical activity since dextro and levo cancel out each
other.
14

15. 15
https://www.youtube.com/watch?v=mm1U-pjRp14
**Image taken from google search engine

16. a) Anomeric carbon
• The carbon atom next to oxygen after cyclization ( not the one attached to
CH2OH) group is called anomeric carbon.
• Which means they differ in configuration at C1 (cyclic) .
• If the CH2OH group is on same side of –OH it is beta.
• If CH2OH is on opposite side of –OH it is alfa.
b) Alfa and beta
An important feature is the direction of the OH group attached to the anomeric
carbon.
Depending on the direction of the OH group, the anomeric carbon is either α or β.
• α: equatorial DOWN or axial DOWN
• β: equatorial UP or axial UP
16

17. Mutarotation
•It is the change in specific optical rotation representing interconversion of alfa and
beta forms of glucose to an equilibrium mixture.
•Interconversion of alfa and beta anomers.
•The alfa and beta anomers as solids are stable but in solution they are
interconvertable.
•The alfa and beta forms of glucose are interconvertable.
Alfa-D-glucose equilibrium mixture beta-D-glucose
+112.2o
+52.7o
+18.7o
17

18. • Fischer Projection: A way of representing an acyclic (open chain) carbohydrate
structure. Vertical lines point away from the viewer and horizontal lines point
toward the viewer.
• Haworth Projection: A way of representing a cyclic (closed chain)
carbohydrate. Substituents can either point up or down on this ring.
18

19. Note : just for your understanding
•Hemiacetal and Hemiketal reaction
1.Hemiacetal: aldehyde and alcohol react to give product which is called
hemiacetal.
2.Hemiketal: ketone and alcohol reacts to give product which is called
hemiketal.
19

20. 20
**Image taken from google search engine

21. 21

22. HOW TO ACTULLY DRAW A CYCLIC STRUCTURE
22
To know weather the groups will lie on left or right we interchange the
position of groups on C-5 carbon.
Therefore, the –CH2OH group will be pointing up in the Haworth projection.
Moreover, the–OH group on the C-2 will be pointing down and its –H substituent
will be pointing up. And, the –OH group on the C-3 will be pointing up while its –H
substituent points down, and so on.
1. The group facing right will project down. (right on
ficher projection is down on haworth)
2. The group facing left will project up. (left on ficher
projection is up on haworth)

23. 23The 6 membered ring is with O is known as Pyranose ring

24. 24
• In fructose the hemiketal reaction takes place between 2nd
carbon and 5th
carbon
therefore we get a 5 membered ring (furanose ring)
CYCLIC / HAWORTH PROJECTION STRUCTURE OF
FRUCTOSE

25. DISACCHARIDES
• Disaccharides are very common.
• It consists of 2 monosaccharides units.
• The two monosaccharides unit are held together by glycosidic bond.
• They are water soluble, sweet to taste.
• Example
Reducing disaccharides- maltose and lactose ( they have free aldehyde or keto
group)
Non reducing disaccharides- sucrose.
25Matose Sucrose

26. GLYCOSIDES
• Glycosides are formed when the aldehyde or keto group reacts
with alcohol or hydroxyl group of alcohol another
carbohydrate or non-carbohydrate.
• The bond so formed is known as glycoside bond.
• The non carbohydrate moiety is referred to as aglycone
• Mono-saccharides are held together by glycosidic bonds to
form di-, oligo- or polysaccharides.
26

27. 1. Maltose
• Maltose is composed of two alfa D-glucose unit held by (1-4) glycosidic bond.
• The free aldehyde group is present on C1 of 2nd
glucose.
• The osazone formation gives sunflower shaped craystals.
• Maltose can be hydrolyzed by dil. Acid to librate 2 molecules of glucose.
27

28. 2. Lactose
• Lactose is commonly known as milk sugar as it is found in milk.
• Lactose is composed of beta-D-galactose and beta D-glucose, held by
glycosidic linkage.
• The anomerric carbon C1 of glucose is free. Hence it is reducing sugar.
• It gives powder puff shaped crystals in osazone test.
• It is hydrolyzed to glucose and galactose.
28

29. 29
**Image taken from google search engine

30. 30
3. Sucrose
• Sucrose is mostly produced by sugar cane.
• It is made up of alfa-D-glucose and beta D-fructose.
• It does not contain free aldehyde or keto group it’s a non reducing sugar and
cannot form osazone.
• It is employed as a sweeting agent in food industry.
Inversion of sucrose
• Sucrose is a dextro rotatory but when hydrolyzed it becomes levo rotatory.
• The process of change of optical rotation is called inversion.
• Hydrolysis of sucrose gives glucose and fructose.
• It can be hydrolyzed by adding conc acid. Once hydrolysed it gives all the test
for reducing sugars positive.

31. POLYSACCHARIDES
• Polysaccharides consists of repeated unit of monosaccharide's held by
glycosidic bond.
• Also known as glycans
• Polysaccharides are linear (straight chained) as well as branched.
• Example- starch, dextrin,insulin, glycogen.
Homopolysaccharides
• On hydrolysis yield only single type of monosaccharides.
• Glucans are polymers of glucose.
• Fructosans are polymers of fructose.
Example- insulin, starch
Heteropolysaccharides
• On hydrolysis yeild mixture of few monosaccharides.
Example- dextrins.
31

32. 1. Starch
• High content of starch is found in cereals, roots, rice, maize etc.
• It is homopolysaccharide composed of D-glucose and held by glycosidic
bond.
• Starch consists of 2 polysaccharides
Amylose- which is water soluble (it is unbranched chain with 200-1000 glucose
lingae held by 1-4 glycosidic bond)
Amylopectin- water insloluble (it is branched consisting of few thousands of
glucose held by 1-6 glycosidic bond).
• Starch is hydrolyzed by enzyme amylase.
32
1-6 linkage

33. Amylose Amylopectin
Straight chain branched
1-4 glycosidic bond 1-6 bond
Water soluble Water in soluble
200-1000 units of
glucose
More than 1000 units
of glucose
33

34. 2. Insulin
It is a polymer of fructose.
Occurs in garlic, onion,dahlia bulbs.
34

35. REACTIONS OF CARBOHYDRATES
1. Dehydration Reaction
• When reacted with conc. sulphuric acid carbohydrates undergo dehydration
reaction with elimination of 3 water molecules.
• On dehydration carbohydrates give furfural or its derivative.
• The furfural or its derivative which is formed condenses with -napthol toɑ
form colored products.
Molish test
• This test is for identification of carbohydrates. This works on principle of
dehydration of carbohydrate by sulphuric acid to give furfural which then
reacts with -napthol to give colored compound.ɑ
35

36. 2. Reduction of carbonyl group
Sugars are classified as
a) Reducing sugars
• Any sugar which is capable of acting as reducing agent because of the free
aldehyde group present is known as reducing sugar.
• They have a free carbonyl group which act as reducing agent.
• They are classified as reducing sugars since they reduce the Cu2+
to Cu+
which
forms as a red precipitate, copper (I) oxide.
Examples : glucose, fructose,lactose,maltose
b) Non reducing sugars
In case of polysaccharides the free carbonyl group is blocked, such carbohydrates
in which there is no free carbonyl group are known as non reducing sugars.
Example: sucrose, raffinose
36

37. Benedicts test
•When carbohydrate is heated with alkaline copper sulphate, copper ions gets
reduced i.e Cu2+
to Cu+
and gives red colored precipitate.
•This test is given positive by all reducing sugars.
•Non reducing sugars give this test negative.
37
**Image taken from google search engine

38. Fehling’s test
Reducing sugar reduces copper ions present in Fehling's solution to give red
precipitate.
Barfoed’s test
This test is done to distinguish between monosaccharides and disaccharides.
This test is used for identification of reducing monosaccharides
Heating should be done only for 1-2 mins as prolonged heating can give false
positive test. Always use waterbath
38

39. Formation of osazone
•When reducing sugar is heated with phenylhydrazine, yellow crystalline
compounds called as osazones are formed.
•In osazone formation first 2 carbons are involved in osazone formation.
•Osazone of different sugars are identified from their crystalline form, time
require for its formation and its melting point.
In this reaction
monosaccharaides give needle shaped crystals.
maltose give sunflower shaped crystals.
Lactose give powder-puff shaped crystals.
39
Glucose Phenylhydrazine Glucose phenylhydrazone
2

40. 40

41. • Difference between reducing and non-reducing sugar
41
REDUCING SUGAR NON REDUCING SUGAR
Possesses free aldehyde/keto group Lacks free aldehyde group
Can reduce Cu2+ ions to Cu+ ions in
Fehling's or benedicts solution
No such reaction takes place
The free carbonyl group acts as
reducing agents
No free carbonyl group present as it is
blocked due to formation of glycoside
bond
Gives benedicts test, Fehling's
test,tommers test positive
Gives benedicts, fehling’s and
tommers test negative
Osazone formation takes place Osazone formation does not take place
Example: maltose, glucose Example: sucrose, raffinose

42. 3. Reduction
• The carbonyl group in sugar can be reduced by variety of reagents such as
hydrogen and platinum to alcohol.
• Carbohydrate (monosaccharides) containing aldehyde or keto group is reduced
to corresponding alcohol.
Glucose H2-Pt sorbitol
42
Monosaccharides Corrosponding alcohol
D-glucose D-sorbitol
D-galactose D-dulcitol
D-mannose D-mannitol

43. 4. Oxidation
• Sugar on oxidation gives acid. Glucose gives gluconic acid, glucaric acid and
glucoronic acid
• The oxidation product depends upon the oxidizing agent used in reaction.
• In this the terminal alcohol or terminal aldehyde or both groups are oxidized.
• Glucose with different oxidizing agents gives different products.
43
Pt-O2
(platinium
dioxide)
Br2
bromine
Nitric acid
Gluconic acid.
Glucoronic acid
Glucaric acid

44. 5. Mucic acid test
• This test is used for identification of galactose and lactose.
• Galactose or lactose on oxidation with conc. Nitric acid gives
galactosaccharic acid (mucic acid).
• The mucic acid is insoluble and gets crystallized.
• The crystals are colorless.
6. Iodine test
Iodine reacts with starch, dextrin glycogen to give colored complex.
44
Types of polysaccharides Colored with iodine
Starch Blue
Dextrin Brown
Glycogen Pink
Amylose Deep blue
Amylopectin Purple

45. DISEASES RELATED TO CARBOHYDRATE METABOLISM
• There are various diseases reported due to abnormal metabolism of
carbohydrates
1. Diabetes mellitus
It is a metabolic disease.
It is caused due to hyperglycemia (excess of glucose in blood stream).
Hyperglycemia is due to defect in insulin action or insulin secretion or both.
Diabetes mellitus are broadly classified into two.
• Type 1 diabetes(insulin dependent or juvenile)
Insulin helps prevent the blood sugar level to get too high.
It mainly occurs in childhood in the age of 12-15 years.
Results due to destruction of insulin producing beta-cells of pancreas (small gland
behind stomach).
In this there is total deficiency of insulin.
Because of its early onset it is called juvenile
Causes: mostly due to genetic disorder.
45

46. 46
Type 2 diabetes (non-insulin dependent)
•It is also known as adult onset diabetes.
•In occurs in adults above 35 years age.
•It is caused due to resistance to insulin action (the body’s cells don't
react to insulin) or there is inadequate secretion of insulin by beta-
cells of pancreas.
•Cause: genetic and environmental.
•Mostly occurs in obese individual.
Common symptoms of both type
•Polyuria (frequent urination)
•Polyphagia (excessive eating)
•Polydipsia (excessive thirst)
Long term effect of diabetes
•Atherosclerosis
•Retinopathy

47. 47
Diabetes management
1.Dietary management
•Low calorie diet and high protein and high fiber rich diet.
•Carbohydrates should be taken from complex sugars like
starches etc.
•Refined sugar should be avoided.
•Diet control and exercise help non-insulin dependent patient.
Hypoglycaemic drugs
•Oral drugs are given to non-insulin dependent patient.
•Tolbutamide, glipizide etc. is used.
•These help in reducing blood glucose level.
Management with insulin.
•Two types of insulin preparations are available, short acting
and long acting.
•Short acting insulin last for 6 hours.
•Long acting lasts for several hours.

48. 48
Type 1 diabetes Type 2 diabetes
Occurs in childhood Occurs in adults
Occurs in age group of 12-15 years Occurs in adults above 35 years age
Body weight of person is normal or low Body weight of person is not normal (obese)
It is caused due to destruction of beta cells Caused due to impairment in production of insulin by beta cells.
The symptoms lasts for weeks The symptoms lasts for months to years
In this administration of insulin is always required In this insulin administration is not required.
Oral diabetic drugs are not useful for treatment Oral diabetic drugs are useful for treatment

49. 2. Glycosuria
When glucose is excreted in urine the condition is known as glycosuria.
It is caused due to high blood glucose levels.
3. Galactosemia
• It is a genetic disorder.
• This is caused due to deficiency of enzyme (galactokinase).
• This enzyme is responsible for conversion of galactose to glucose.
• This condition is known as galactosemia.
• This condition is characterized by increased galactose level in urine and in
blood.
• The accumulated galactose is converted into galactitol, which is responsible
for development of cataract.
Symptoms
Jaundice
Mental retardation
49

50. 4. Fructose intolerance
• Fructose is a normal sugar present in fruits.
• When taken in it gets metabolized to give energy and CO2.
• Fructose intolerance is a digestive disorder in which absorption of fructose is
impaired.
• In this there is defect in metabolism of fructose from small intestine.
• This results in increased concentration of fructose in intestine.
5. Glycogen storage disease
The diseases which cause abnormality in glycogen (polysaccharide) synthesis and
breakdown are termed as glycogen storage disease.
50

51. MUCOPOLYSACCHARIDES (complex polysaccharides containing amino
group))
• Mucopolysaccharides are made up of repeating units of sugar derivaties,
namely amino sugar and uronic acid.
• They are long unbranched polysaccharides consisting of reappeared
disaccharide unit.
• They are commonly known as glycosamnioglycans (GAG)
• Such molecules contain amino, carboxyl, sulphate group which makes
them acidic.
• They are found throughout the body.
• Also found in fluid that lubricates joints.
• Present in connective tissues.
• Chondrotin is found in mammalian tissue (bone, heart,skin, cornea)
• Mucopolysaccharides are sometimes found in combination with protein to
form mucoprotein or proteoglycans
• Mucoprotein contain 95% carbohydrate and 5% protein.
• Mucopolysaccharides are essential components of tissue structure.
Example: Hyaluronic acid (consists) 250-2500 disaccharide units, chondroitin51

52. 52
**Image taken from google search engine

53. QUESTIONS
1. Define carbohydrate. Classify it with examples. Write its biomedical
importance.
2. Write notes on Mucopolysaccharides and proteoglycans.
3. Define Carbohydrates and give their classification with examples.
4. Give the principles of the following tests :
1) Molosch’s test 4) fehlings 6)tommers 7)
2) 2) Benedict’s test
3) Osazone test
5. What is mutarotation ? Explain Optical Isomerism
6. What is Juvenile diabetes? Discuss in brief about Diabetes.
7. Define enantiomers, anomers, levo and dextro rotatory.
8. Short note on diseases caused due to carbohydrate metablosim.
9. What are carbohydrates? Difference between reducing and non reducing
sugars based on qualitative tests.
10. Structure of glucose, fructose,maltose,lactose,sucrose,
53

54. • Composition of starch and its components.
• Define epimers, anomers, steriomers,assymetric carbon.
• Different chemical test for carbohydrates.
• Functions of carbohydrates
• Short note on monosaccharaides, disaccharides, polysaccharides
• What is inversion of sucrose.
• Racemic mixture
54