• Carbohydrates are polyhydroxy aldehydes or ketones or
compounds derived from their hydrolysis.

• Carbohydrates are the most abundant organic constituents
of plants.

• They are the major source of chemical energy for living
organism (e.g. Sugars & Starch).

• It compassed of carbon, Hydrogen and Oxygen.

• The general molecular formula of carbohydrates is c(H2O).
Starch and cellulose are two common carbohydrates.

Role of Carbohydrates:

• Carbohydrates are the major source of energy in animal

• Carbohydrates are helpful in the absorption of calcium are
phosphorus in younger people.

• They help in the secretin of digestive juices in
gastrointestinal tract.

• They help in peristaltic movement of food.

• They maintain Glucose level in plasma.

Classification of


• Carbohydrates that cannot be hydrolyzed to simpler
compound are called Monosaccharide.

• Monosaccharaides have the one sugar molecule.


• Carbohydrates that give two monomeric unit on hydrolysis
are called Disaccharides.

• E.g. Maltose, Sucrose, Lactose.

They have two sugar molecules.

1.  Oligosaccharides:-

• Carbohydrates that gives There to (10) ten monosaccharide
on hydrolysis are called oligosaccharides.

• E.g: Reffinose, Maltotriose.

• They have two or ten sugar molecules.

1.  Polysaccharides:

• Carbohydrates that give many monosaccharide on hydrolysis
are called polysaccharides.

• They have ten or more sugar molecules.

• Polysaccharides are made-up of one or different types of


1.  Homopolysaccharides:

• The monomeric units are arranged in the form of long chain
either unbranched or branched.

• E.g: Starch, Glycogen, Cellulose etc.


• Hemicellulose is a polymer containing D-xylose,
L-arabinoc, D-Galactose, L- Rhamnose, D-Monnose and D-Glucoronic acid

• e.g.: Heparin

3.  Mucopolysaccharides:

On hydrolysis mucopolysaccharides give amino sugars acetylated
sugar and uranic acids.

Mucopolysaccharides are important biological substance.

Chemical reactions
and Qualitative teste for Carbohydrates:-

1. Dehydration:-

on dehydration give for fural or its derivative.

      Concentrated sulphuric
acid is used as a dehydrating agent.

Molisch test:

• It is general test for Carbohydrates identification.

• Furfural or its derivative formed during dehydration,
react with α-nepenthes to give violet colour.

• In this test concentrated sulphuric acid is used as a
dehydrating agent.

2. Reactions of
carbonyl group:

1) Benedict’s test –

      Carbohydrate is
wanted with alkaline copper sulphates.

      Copper ions get
reduced and give red precipitate of cuprous oxide.

Note:- All
reducing Sugars give this test positive while sugar like sucrose does not give
this test positive.

2) Barfoed’s test:

• This test’s used for the identification of reducing

• In presence of weak acidic condition only mono-saccharidies
can reduce copper ion to give red precipitate.

3) Fehling’s Test:-

• Reducing sugar reduces the copper ions present in the
Fehling solution so as to give red precipitate.

4) Formation of

• When reducing Sugar is heated with phenyldyrazine yellow
crystalline compound called osazones are formed.

• E.g. D-Glucose +Phenylhydrazine →Glucose (Yellow crystal)
Phenyldyrazine + H2O

3. Reduction:-

• The carbonyl group of sugar can be reduced by variety of
reagents such as Hydrogen and platinum to an alcohol.

• Such Carbohydrate derivatives are called alditols.

• Important example are sorbitol glycerol rabitol.

4. Oxidation:

• Sugar are oxidation gives acid. The oxidation product
depends upon oxidizing agent used in the reaction.

• E.g. Glucose is oxidising to different products with the
help of different oxidizing agents.

5. Mucic Acid test:

• This is used for identification of galactose and lactose.

• Galactose or Lactose on oxidation in presence of conc.
Nitric acid gives galactosaccharid acid (Mucic Acid).

6. Iodine test:

• Iodine reacts with starch dextrin and Glycogen to form a
coloured complex.

                          Type of Polysaccharide                                       Colour with Iodine

1                                Starch                                                            Blue

2                                Dextrin                                                          Brown

3                                 Glycogen                                                     Pink

4                                 Amylose                                                       Deep Blue

5                                Amylopectin                                                  Purple

Disease related to
Carbohydrate metabolism:-

• Various disorders have been reported due to abnormal
metabolism of Carbohydrates.

A) Diabetes

• It is a group of metabolic disorders with a common
characteristics feature of hyperglycemia.

• Hyperglycemia in diabetes mellitus due to defect in insulin
action insulin secretion or both.

• Diabetes comes from the Greek words “Siphon” and implies that
a lot of urine is made.

• The second term Mellitus come from the Latin word “Mel”
which means Honey.

Diabetes mellitus is broadly classified into 2 categories.

1.  a) Type 1 Diabetes

2.  b) Type 2 Diabetes

a) Type 1 Diabetes:-

• It is characterized by absolute deficiency of insulin due
to distruction of B-cell of pancreas.

• A chronic condition in which the pancreas produce little
or no insulin.


      Increase Thrust




b) Type 2 Diabetes:-

• This this type of diabetes a due to inadequate secretion
of insulin by B- cells of pancreas.

• In this type of diabetes the body either does not produce
enough insulin.


      Increase thirst

Urination hanger


      Blurred vision.

Note:- Normal range- (70-120mg/dl) High range – (←200mg/dl)

B) Glycosuria:-

      when Glucose is
excreted in urine the condition is called as glycosuria.

occurs due to elevated blood glucose level.

      Glycosuria more
common during pregnancy.

C) Galactosemia:-

      Due to
deficiency of enzyme galactose 1-phosphate luridly transferees and Galactosemia.

cannot be converted in glucose which leads to a condition called as Galactosemia.

      It is
characterized by increased galactose level in circulation and urine.

galactose into galactic which responsible for development of cataract.




retardation, etc.

D) Fructose

• One of the very normal hexose sugars of fruits (i.e.
Fructose) gets normally metabolised to give energy and CO2 but defective
metabolism of fructose developed in blood, disorder known as fructose in

• This disease occurs when calls on the surface of the
intestine are not able to break down fructose efficiently.

E) Glycogen storage

• The metabolic abnormalities related with glycogen
synthesis is termed as glycogen storage disease.

• Glycogen is main source of energy when an enzyme is
missing glycogen can build up in the liver or glycogen may not form properly.


      Not growing
fast enough

      Low blood sugar

      Weak muscles.

importance of Carbohydrates:-

1.  Carbohydrates are
important constituents of the cell structures in the form of glycolipid,
glycoprotein, heparin, cellulose, starch, Glycogen.

2.  Carbohydrates
serie as an important source and store of energy.

• Carbohydrates are important basic material for many
organic compounds like- Amino acids, Nucleic acid, Lipids.

1.  Carbohydrates are
important row material for the industrial production of products like –
Glucose, maltose, alcohol, Acids etc.

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