ST.
XAVIER’S INSITUTION,
PANIHATI
CHEMISTRY
CLASS 12
CARBOHYDRATE
Monosaccharides:
These are the compounds which do not break into simpler compounds on
hydrolysis. If it contains aldehyde group is known as aldose (Glucose) and if it
contains keto group is known as ketose (Fructose).
Oligosaccharides:
These compounds give two to nine monosaccharide molecules on acidic
hydrolysis. These are also known as di, tri or tetra-saccharides depending on
the actual number of the monosaccharide molecules formed during hydrolysis.
Disaccharide – Sucrose (C12H22O11)
Trisaccharide- Raffinose (C18H32O16)
Tetrasaccharide- Stachyose (C24H42O21)
Carbohydrates which reduce Tollen’s reagent or Fehling solution are called
reducing carbohydrate or reducing sugar (glucose). They contain aldehyde (-
CHO) group.
Which do not reduce these reagents are called non-reducing sugar (sucrose).
They contain ketone (-CO-) group.
STRUCTURE OF GLUCOSE:
Glucose contains 4 chiral carbon atoms.
STRUCTURE OF FRUCTOSE:
There are three chiral carbons in fructose.
Q. Although fructose has keto group but it reacts with Tollens’ reagent and
Fehlings’ solution. Explain why.
Ans. In the reaction medium, fructose undergoes enolisation to form –CHO
group so it reacts with Fehlings’ solution and Tollen’s Reagent. So by using
Tollen’s reagent and Fehlings’ solution, glucose and fructose cannot be
separated chemically. It is only possible by Bromine water test.
OXIDATION OF FRUCTOSE:
In oxidation of Fructose, C-C bond breaking takes place so strong oxidising
agents like conc. HNO3 is required.
REACTIONS OF GLUCOSE:
How will you prove Glucose has 5 –OH groups?
Ans. One mole of glucose on reaction with 5 moles of acetic anhydride forms
glucose penta-acetate and 5 moles of acetic acid as by-product.
Reaction with HI:
Reaction with NH2OH (hydroxylamine):
Reaction with Bromine water:
Due to the presence of (-CHO) group glucose decolorizes Br2 water but
fructose is not oxidized by Br2 water. (Distinguish between glucose and
fructose).
Reaction with HNO3:
Reaction with HCN:
Reaction with Tollens’ Reagent
Reaction with Fehlings’ reagent
REACTION WITH PHENYL HYDRAZINE:
Glucose and fructose on reaction with excess phenyl hydrazine forms light
yellow precipitate of Glucose lusazone or osazone. This is known as osazone
test. The ratio of glucose to phenyl hydrazine is 1:3.
Structure of sucrose:
The linkage holding two units of monosaccharides is called a glycosidic linkage.
Starch is the polymer of α-glucose while the cellulose is the polymer of β-
glucose.
Cellulose does not get hydrolysed to glucose in our body due to the absence
of cellulose enzyme.
AMINO ACIDS
Q. Define isoelectric point and write the zwitter ion structure of Glycine.
A zwitter ion is a dipolar structure formed by the neutralisation of acid and
basic centres present within the molecule.
ZWITTER ION OF GLYCINE
The pH at which there is no net migration of amino acid molecules towards any
electrode is called isoelectric point of the amino acid. The isoelectric point of
Glycine is 6.082.
Fibrous protein:
These are linear condensation products of amino acids, soluble in strong acids
and bases but insoluble in water. These can resist small change in pH and
temperature. Example- keratin in skin, hair; collagen in tendons: myosin in
muscles; fibrosin in milk.
Globular protein:
These are cross-linked condensation products of amino acids, soluble in water,
acid, bases and salts. These cannot resist changes in pH and temperature
Globular protein.
Globular Protein Fibrous protein
• The polypeptide chain is folded, • The polypeptide chains are extended.
hooked and twisted.
• Packed structure • Less compact
• Examples: Myoglobin, antigen, • Examples: Keratin, collagen.
enzymes.
Denaturation of protein:
When a globular (water soluble) protein is subjected to a change in
temperature and pH, the secondary and tertiary structures are destroyed but
primary structure remains intact, this known as denaturation of protein. Due
to this denaturation, coagulation or precipitation takes place and it loses its
biological activity and such a protein is called denatured protein. The
coagulation of white part of an egg on boiling is an example of denaturation of
protein. It can be caused by (1) heat, (2) action of bacteria, (3) shaking of
alcohol and (4) treatment with concentrated acids.
Structures of Protein:
NUCLEIC ACID
A nitrogen containing organic base with ring structure present in nucleic acid
are known as purines or pyrimidines. The bases derived from purines are:
Adenine (A) and Guanine (G). The bases derived from pyrimidines are Cytosine
(C), Thymine (T) and Uracil (U).
DNA (deoxy-ribonucleic acid):
The purine bases present in DNA are – Adenine (A), Guanine (G)
The pyrimidine bases present in DNA – Thymine (T), Cytosine (C)
RNA (Ribonucleic Acid):
The purine bases present in RNA are – Adenine (A), Guanine (G)
The pyrimidine bases present in RNA are – Cytosine (C), Uracil (U)
Difference between DNA and RNA:
• The sugar molecule found in RNA is D-ribose, while the sugar in DNA is D-2-
deoxyribose. The sugar D-2-deoxyribose differs from ribose only in the
substitution of hydrogen for an (-OH) group 2-position.
• RNA contains the base Uracil but the base Thymine is not present in it. On
the other hand, the base thymine is present in DNA but Uracil is absent.
• RNA is single helix strand, while two helix strands are wound together to
form a double helix in case of DNA.
STRUCTURE OF DNA:
VITAMINS
Water soluble vitamins: B, C
Fat soluble vitamins: A, D, E, K
Name of vitamin Source Deficiency diseases
1. vitamin A Carrot, butter, milk Night blindness
(Retinol)
2. vitamin B1 Green vegetables, milk Beri-beri (paralysis of
(Thiamine) leg)
3. vitamin B2 Milk, egg-white, liver Fissuring of the corners
(Riboflavin) of the mouth and lips.
4. vitamin B6 Milk, cereal, egg-white Convulsions
(Pyridoxine)
5. vitamin B12 Curd, meat, fish Pernicious anaemia
(Cyanocobalamine)
6. vitamin C Citrus fruits (amla) Scurvy
(Ascorbic acid)
7. vitamin D Fish, egg, milk, Exposure Ricket(Bone
(Ergocalciferol) to sunlight. deformation in children)
Osteomalacia (soft
bones and joint pain in
adults)
8. vitamin E Oil Sterility, increased
(Tocopherol) porosity of bones and
muscular weakness.
9. vitamin K Green leafy vegetables, Increased blood clotting
(Phylloquinone) cereals time and haemorrhage.
