Chemistry project on proteins and its classification in details by @sushant juneja

1. K.L.MEHTA DAYANAND PUBLIC
SR. SEC. SCHOOL NO. 1, NIT
FBD (2017-18)
CHEMISTRY PROJECT
ON
PROTEINS
SUBMITTED BY:
SUSHANT JUNEJA.
12TH .A,
SUBMITTED TO:
MRS. INDERPREET SUJLANA
SIGN.________________

2. CERTIFICATE
This is to certifies that SUSHANT
JUNEJA of a student class XII-A
has successfully completed the
chemistry project on the topic
proteins under the guidance of
Mrs. Inderpreet Sujlana (subject
teacher ).
Signature
(Subject teacher)
_______________

3. ACKNOWLEDGEMENT
S
I Have Taken Efforts In This Project.
However, It Would Not Have Been
Possible Without The Kind Support And
Help Of Many Individuals.
I Would Like To Thank My Principal Dr.
Geeta Yadav And School For Providing
Me With Facilities Required To Do My
Project.
I Am Highly Indebted To My Chemistry
Teacher, Mrs. INDERPREET SUJLANA,
For Her Invaluable Guidance Which Has
Sustained My Efforts In All The Stages
Of This Project Work.
I Would Also Like To Thank My Parents
For Their Continuous Support And
Encouragement.
My Thanks And Appreciations Also Go
To My Fellow Classmates And The
Laboratory Assistant In Developing The
Project And To The People Who Have
Willingly Helped Me Out With Their
Abilities.

4. INTRODUCTION.
α-AMINO ACIDS:-
STRUCTURE .
NOMENCLATURE.
CLASSIFICATION.
STRUCTURE OF PROTEIN:-
PRIMARY
SECONDARY
TERTIARY
QUATNERY
CLASSIFICATION OF PROTEINS.
ISOELECTRIC pH.
PROTEIN DENATURATION.

5. Proteins

6. α-Amino Acids
In these acids an amino group is
present on the α-carbon atom (i.e.,
carbon next to the carboxyl group).
Their general formula is;
There are 20 commonly occurring
α-amino acids in proteins and 6 are
found in special tissues .

7. These amino acid s differ with
respect to the nature of their side
chain groups R. The properties of
amino acid side chains determine
the properties of the proteins they
constitute.
Structure of
Amino Acids
Amino acids contains both an
acidic (-COOH) group and a basic
(-NH2) group. In fact these groups
interact resulting in the transfer
of a proton from acidic carboxylic
acid group to amino group thereby
resulting in the formation of an
internal salt.

8. The dipolar structure of internal
salt is also known as zwitter ion.
Except glycene all amino acids are
optically active. The α-carbon atom
of amino acids (except glycene) is
asymmetric, therefore, two stereo
isomers are possible, which are
mirror images of each other.

9. These two isomers are called D- and
L- isomers depending upon the
configuration around the
asymmetric carbon atom. However,
all the naturally occuring amino
acids belong to L- series.
NOTE:- If the –NH2 group at the α-
carbon lies on the left side as the
-OH group in glyceraldehyde, the
amino acid is said to belong to L-
series. On the other hand, if the
–NH2 group at the α-carbon lies on

10. the right hand side as the -OH
group in D-glyceraldehyde, the
amino acid is said to belong to D-
series .
Nomenclature
of Amino Acids
Amino acids are generally known
by their common names. Further
these names are also abbreviated to
a standard code. The standard code

11. Usually consists of the first letters
of the common name.
Common
name
Abbreviated
name
Side chain (R) symbol
Glycine Gly -H G
Alanine Ala -CH3 A
Valine* Val (H3C)2CH- V
Leucine* Leu (H3C)2CHCH2- L
Isoelucine* Ile (CH3)2CH2CH- I
Threonine* Thr H3C-CHOH- T
Lysine* Lys H2N-(CH2)4- K
Glutamic
Acid
Glu HOOC-(CH2)2- E
Aspartic
Acid
Asp HOOC-CH2- D

12. * essential amino acids
 Classification
of amino Acids
Amino acids can be classified in a
number of ways.
 Neutral, acidic and basic amino
acids:-
Amino acids which contains one
–NH2 group and one –COOH
group are called Neutral amino
acids. For ex:- Glycine, Alanine
etc.
Common
name
Abbreviated
name
Side chain
(R)
Symbol
Serine Ser HO-CH2- S
Cysteine Cys HS-CH2- C
Phenyl
Alanine*
Phe C6H5-CH2- F

13. Amino acids which contains one
–NH2 group but two –COOH
groups are called Acidic amino
acids. For ex:-Aspartic acid,
Glutamic acid etc.
Amino acids which contains two
–NH2 groups and one –COOH
group are called Basic amino
acids.
 Essential and non- essential
amino acids:-
Amino acids can also be
classified as essential and non-
essential amino acids. Out of the
twenty amino acids required for
the synthesis of various
proteins, human body can
synthesis only ten. The
remaining ten amino acids must

14. be supplied in the diet and are
thus called essential amino acids.
The ten amino acids which
human body can synthesis are
known as non- essential amino
acids.
Ten essential amino acids are:-
(a) Valine (b) Leucine
(c) Isoleucine (d) phenylalanine
(e) Methionine (f)Tryptophen
(g) Threonine (h)Lysine
(i) Arginine (j)Histidine
Structure of
Proteins
Peptides are the condensation
products of two or more α-amino

15. acids. Condensation involves the
elimination of water molecule
between the –NH2 group of one
amino acid molecule and –COOH
group of another amino acid
molecule.
Peptides can be classified as
dipeptides, tripeptides and
polypeptides depending upon the

16. number of amino acid molecules
taking part in the condensation.
For ex:- if condensation takes place
between two α-amino acid
molecules the product formed is
called a dipeptide and the
–CO-NH- bond is called peptide
bond or peptide linkage.
The complete structure of a
protein is quite complex.
Therefore, their structures are
usually distributed at different
levels.

17.  Primary structure:- It refers
to the sequence in which the
various amino acids are linked
to one and another in a protein.
It tells us the covalent structure ,
including the disulphide bridges of
a proteins.
The primary structure of a proteins
is determined by its successive
hydrolysis with acid, alkalis or
enzymes. Successive hydrolysis
yield different products having
decreasing molecular masses as
shown below.

18. PRIMARYSTRUCTURES

19. • Proteins
• Proteoses
• Peptones
• Poly peptides
• Simple peptides
• α-Amino acids

20.  Secondary structure :- It
refers to the conformation which
the polypeptide chains assume
as a result of hydrogen bonding
between the carboxylic acid and
amino groups.
Depending upon the
size of the R- group,
two different
secondary structures
are possible.
(A) α-helix structure:-
If the size of the R-
group is quite large,
the hydrogen bonding (inter
molecular) occurs between
>C=O group of one amino acid
unit and the >N-H group of the
fourth amino acid unit in the

21. chain. As a result the polypeptide
chain coils up into a spiral
structure called right handed α-
helix structure.
The α-coil may at places be much
less regular, forming random
coils. Most of the fibrous proteins
like α-keratin in hair , nail,
myosin in muscles have α-helix
structure. On the other hand,

22. globular proteins have certain
segments of α-helix structure.
(B)β-Pleated sheet structure:-
If R- group are small, the peptides
chains lie side by side in a zig-zag
manner with alternate R- groups
on the same side situated at fixed
distances apart. The two such
neighbourings chains are held
together by intermolecular
hydrogen bonds.

23. A number of such chains can be
inter-bounded and this results in
the formation of a flat sheet
structure. These chains may
contract or bend a little in order to
accommodate moderate sized R-
groups. As a result the sheet bends
into parallel folds to form pleated
sheet structure known as β-pleated
sheet structure.

24. (C) Tertiary structure:- Tertiary
structure of a protein refers to its
complete three-dimensional
structure. It arises due to folding
and superimposition of various
secondary structural elements to
give the entire molecule a spherical
shape. At normal pH and
temperature, each protein will take
a shape that is energetically most
stable. This shape is specific to a
given amino acid sequence and is
called the native state of protein.
Once amino acids join up to form
the primary structure , the
subsequent structures follow
automatically. This is governed by
the attractive and repulsive forces
between different parts of the

25. polypeptide. Thus, we can say that
the primary structure of a protein
dictates its tertiary structure.

26. (D) Quaternary structure:-
Certain proteins consist of a bundle
two or more polypeptides chains.
Each such chain in these proteins
have an appropriate primary,
secondary and tertiary structure.
Such proteins have quaternary
structure also. Some examples of
proteins having quaternary structure
are insulin, haemoglobin and ferritin
(found in liver). Insulin have two
polypeptides chains linked by
disulphide bridges, haemoglobin has
four chain, two α-chains and two β-
chains and ferritin has twenty
identical polypeptides chains.

28. Classification
of Proteins
Protein can be classified in a number
of ways.
On the basis of functions:-
1. Catalytic proteins or
enzymes:-
Glycokinase,Dehydrogenase.
2. Transport Proteins:-
Haemoglobin, Transferrin.
3. Storage Proteins:-
Ferritin, Myoglobin.
4. Contractile proteins:-
Actin, Myosin.
5. Structural proteins:-
collagen, Keratin.

29. On the basis of shape:-
Globular
Protein
Fibrous
Protein
Soluble. Insoluble.
Spherical or oval in
shape.
Elongated or needle
shape.
Axial ratio<10. Axial ratio>10.
Low molecular weight. High molecular weight.
Eg: Albumin, Globin,
Histones.
Eg: collagen, elastin.

30. The pH of the solution influences
net charge of protein molecule
dissolved in it.
At lower pH, proteins carry
relatively more of +ve charge and at
higher pH, relatively more of –ve
charge.
At the isoelectric pH
“Isoelectric pH (pI) of a protein
molecule is the pH at which it carries
no net charge.”

31. The net charge is zero.
Minimum water solubility.
Maximum precipitation.
Isoelectric pH (pI) of a protein is
determined by
•Amino acids composition.
•All the ionisable groups .
Protein
denaturation:-
pI of CASEIN
4.6
pI of albumin
4.7

32. Protein denaturing Agent:-
Physical
Agents
Heat
UV-
Radiation
X- Ray
Chemical
Agents
Acids
Alkalies
Urea

33. Loss of 3- dimensional structure.
Loss of biological activity.
Usually irreversible, some cases
reversible.
Decreases solubility, causes
precipitation.
Increases digestibility of proteins.

34. NCERT Textbook.
PRADEEP fundamental
chemistry.
www.wikipedia.co.org
www.goo.gl.com
DINESH A2Z chemistry.
www.meritnation.co.in