3. SOURCE OF PROTEINS
PLANT SOURCE:
grains,cereals,legumens,nuts ,seeds,
fruits,roots and tubers like
yams,cassava,and sweet potato.
ANIMAL SOURCE:
meat,egg,fish and milk and milk derived
food
4. INTRODUCTION
Proteins are polymers of
amino acids
bonded by peptide linkages.
Their molecular weights range from 5000
to many millions.
They occur in all living cells.
They are present in muscle, skin, hair and
other tissues that make up the body’s nonbony structure.
5. As enzymes they catalyze
biochemical reactions.
As hormones they regulate
metabolic processes.
8. According to this system, proteins
are divided into two classes;
1. SIMPLE PROTEINS:
The simple proteins are those
which are made of chains of
amino acid units only, joined by
amide linkages.
Upon hydrolysis, they yield
mixtures of amino acids and
nothing else.
10. 2.CONJUGATED PROTEINS:
These molecules are made of a simple
protein united covalently or noncovalently with a non-protein factor.
The non-protein portion is called
prosthetic group or cofactor.
Examples:
Glyco-protein
Phospho-proteins
Chromo-proteins
12. This shape-classification divides protein
into two types depending on their molecular
shape:
1.
FIBROUS PROTEIN:
In these proteins the poly-peptide
chains coil about one another and are
held together by strong inter-chain
hydrogen bond.
Thus their molecules assume the shape
of large linear fibers which are used
for connections, support, and the
structure in living organisms.
14. 2.GLOBULAR PROTEINS
Their molecules are globular or
roughly spherical in shape.
They are made of poly-peptide
chains coiled back and forth on
themselves so as to make compact
spheroid molecules.
The poly-peptide chains are held
together firmly by inter chain
hydrogen bonds.
15. Globular proteins are generally soluble in
water or solution of acids, bases and salts.
The function of globular proteins is to
maintain and regulate life processes in the
living organism.
Examples:
Enzymes
Insulin
Hemoglobin
Antibodies
Cytochromes
16. STRUCTURE OF PROTEINS
The proteins are made up of polymers of amino
acid by peptide bonding, hence its basic structure
will be:
17. Proteins have a complex 3-dimensional structure.
It is studied step by step at four different
levels, rather than as a whole.
1. Primary structure
2. Secondary structure
3. Tertiary structure
4. Quaternary structure
18. PRIMARY STRUCTURE
The primary structure of a protein refers to the
sequence of amino acid.
The amino acid sequence in many proteins have been
determined and following observations are made:
1. A protein may contain more than one amino acid
chain.
2. Sequence of amino acids in the protein chain is
essentially random.
3. Small variation in the sequence of amino acid have
pronounced effects on the properties of protein.
19.
20. SECONDARY STRUCTURE
The secondary structure of a protein
refers to the shape in which long amino
acid chains exist.
Many proteins consist of amino acid chain
coiled into a spiral known as an -helix.
The spiral is held together by hydrogen
bonds between N-H and C=O groups
vertically adjacent to one another in the
helix.
21.
22. TERTIARY STRUCTURE
An
-helix may be considered to be a
piece of rope which is free to bend twist
and fold.
The tertiary structure of a protein
refers to the final 3-dimensional shape
that results from twisting, bending and
folding of protein helix.
23.
24. QUATERNARY STRUCTURE
Complex proteins are often form from two
or more amino acid chains rather then a
single amino acid chain.
Each chain is a complete protein with a
characteristic primary, secondary and
tertiary structure.
The quaternary structure refers to the
way in which these amino acid chains of a
complex protein are associated with each
other.
25.
26.
27.
28. GENERAL PROPERTIES
Most proteins are colorless amorphous solid.
They have no definite melting point.
Proteins like amino acids, exists as
zwitterions.
Most proteins are optically active.
Proteins, like amino acid, have isoelectric
points.
Proteins form colloidal dispersion in
water.They can pass through a filter paper but
not through a membrane.
29. Proteins are easily precipitated :
By heat
By ethyl alcohol
By conc. inorganic acid
By silver nitrate
By picric acid or tannic acid
By uv rays and x-rays
Simple proteins can be hydrolysed with acids
(HCl),alkalies (NaOH),or enzymes to give
component amino acid.
Proteins are oxidized on burning and
putrification.The product include N,CO2 and
1.
2.
3.
4.
5.
6.
water.
