Proteins, Carbohydrates

1. Quick Review
Biomolecules
IIT-JEE –Mains
By
Halavath Ramesh
Chemistry

3. Biomolecules
 Biomolecules are organic molecules, which build up living
organisms and are required for their growth and maintenance.
 A living system grows, sustains and reproduces itself.
 The most amazing thing about a living system is that it is
composed of non-living atoms and molecules.
 The living systems are made up of various complex
biomolecules like carbohydrates, proteins , lipids, nucleic
acids, vitamins, hormones etc
 “ It is the harmonious and synchronous progress of chemical
reactions in body which leads to life”.

4. Proteins
 Proteins are the most abundant biomolecules of the living system.
 Chief sources of proteins are milk, cheese, pulses, peanuts fish, meat etc.
They occur in every part of the body and form the fundamental basis of
structure and functions of life. They are also required for growth and
maintenance of body.
 The word protein is derived from Greek word” proteios” which means
primary or of prime importance.

5.  Proteins are complex nitrogenous organic macromolecules found
in the living systems.
 They are essential for the living organisms to perform a large
number of biological functions.
 Proteins are polypeptides formed by the polymerization of amino
acids.
 Amino acids: Amino acids are compounds containing both amino
(-NH2) and carboxyl (-COOH) groups.
 They may be classified as ɑ, β,ɤ etc depending upon the position
of the amino group with respect to the carboxyl group.
 Amino acids forms proteins.

6. ɑ-Amino acid: Those amino acids in which –NH2 group and -COOH group are
attached to same carbon are called “ ɑ-Amino acids”. These are obtained by hydrolysis
of proteins e.g., glycine.
Types of Amino acids:
1. Acidic, Basic and Neutral Amino Acids:
If equal number of amino acid and carboxyl group is present. It is neutral.
More number of amino than carbonyl group makes it basic and more carboxyl group
as compared to amino makes it acidic.
2. Essential and Non-essential Amino Acids:
The amino acids, which can be synthesised in the body, are known as non-essential
amino acids.e.g., glycine, alanine, glutamine etc. On the other hand those which
can not be synthesised in the body and must be obtained by diet are known as
essential amino acids.

7. Classification of proteins: Proteins are classified as follows
(a) Based on molecular shape:
1. Fibrous proteins:
2. Globular proteins
(b) Based on structure and shape:
1. Primary structure
2. Secondary structure
3. Tertiary structure
4. Quaternary structure

8. Non-polar Amino acids:
1. Glycine
2. Alanine
3. Valine
4. Leucine
5. Isoleucine
6. Phenylalanine
7. Methionine
8. Tryptophan
9. Proline

9. Polar Amino Acid: ( Neutral)
10. Serine
11. Cysteine
12.Asparagine
13.Glutamine
14. Threonine
15. Tyrosine

10. Acidic Amino Acids:
16. Aspartic acid
17. Glutamic acid
Basic Amino Acid
18. Lysine
19. Arginine
20. Histidine

11. Different Proteins and their Functions:
1. Enzyme---Trypsin, Pepsin-As a catalyst in
biochemical reactions.
2. Structural ---Collagen, Keratin-Structure and
protective action in teeth, nails and hairs
3. Transport---Haemoglobin-Transport of oxygen from
lungs by blood stream to different tissues.
4. Motion-Myosin ,Actin-For motion of muscles.
5. Storage-Myoglobin-storage of oxygen in muscles.
6. Storage house-Albumin,casein-Food for chick,
complete food for new born baby.

12. We distinguish the following structural levels for
proteins
1.The primary structure is the amino acid sequence.
2. The secondary structure is the arrangement of the amino
acids in space.
3. The tertiary structure is the three-dimensional folding
pattern, which is super imposed on the secondary structure .
4. The quaternary structure is the composition of two or more
polypeptides.

13. Protein Synthesis
“ DNA makes RNA makes proteins” said Marshall Nirenberg
 In molecular biology and genetics, translation is the third
stage of protein biosynthesis( part of the overall process of
gene expression). In translation messenger RNA (mRNA)
produced by transcription is decoded by the ribosome to
produce to produce a specific amino acid chain, or
polypeptide that will later fold into an active protein.

14.  Many types of transcribed RNA such as transfer RNA,
ribosomal RNA, and small nuclear RNA, do not under go
translation into proteins.
 Translation proceeds in four phases: initiation, elongation,
translocation and termination( all describing the growth of the
amino acid chain, or polypeptide that is the product of translation).
 Amino acids are brought to ribosome's and assembled into
proteins.
 In activation the correct amino acid is covalently bonded to the
correct transfer RNA(tRNA) .
 The amino acid is joined by its carboxyl group to the 3’ OH of
the tRNA by an ester bond.

15. Denaturation of Proteins: When a protein in its native
form is subjected to change ,like change in temperature
or pH, the hydrogen bonds are disturbed. Due to this
,globules unfold and helix get uncoiled and protein
loses its biological activity. It is called Denaturation of
protein. During Denaturation 2° and 3° structure are
destroyed but 1° structure remains intact. E.g.
Coagulation of egg white on boiling , curding of milk
etc.

16. 1. How can you explain the Amphoteric nature of amino acids ?
ANS: Amino acid consists of both acidic( carboxyl group) and
basic (amino group) groups in the same molecule. The carboxyl
group can lose a proton and amino group can accept a proton in
aqueous solution giving rise to a dipolar ion known as Zwitter
ion. This is neutral and contain both positive and negative
charges. Amino acids show Amphoteric behaviour as they react
with both acids and bases.

17. Objective Questions
1. Thiol group is present in
a. Cystine
b. Cysteine
c. Methionine
d. Cytosine
2. Which of the vitamins given below is water soluble?
a. Vitamin C
b. Vitamin D
c. Vitamin E
d. Vitamin K

18. 3. Which of the following compounds can form a zwitter ion ....
a. Aniline
b. Acetanilide
c. Benzoic acid
d. Glycine
4. Assertion: Amino acids are soluble in benzene and ether.
Reason: Amino acids exist as Zwitter ions.
a. If both assertion and reason are true and the reason is the correct
explanation of the assertion.
b. If both assertion and reason are true but reason is not the correct
explanation of the assertion.
c. If assertion is true but reason is false.
d. If the assertion and reason both are false.
e. If assertion is false but reason is true.

19. 5. Amino acids are ......
a. Liquids
b. Volatile solids
c. Non- volatile crystalline compounds
d. Mixture of amines and acids
6. Isoelectric point is a .....
a. Specific temperature
b. Suitable concentration of amino acid
c. Hydrogen ion concentration that does not allow migration of
amino acid under electric field.
d. Melting point of an amino acid under the influence of electric
field

20. 7. Metal present in blood is ......
a. Al
b. Mg
c. Cu
d. Fe
8. Insulin is......
a. An amino acid
b. Protein
c. A carbohydrate
d. A lipid

22. Halavath Ramesh