Proteins are macromolecules formed by amino acids. Proteins are large size molecules (macromolecules), polymers of structural units called amino acids. A total of 20 different amino acids exist in proteins and hundreds to thousands of these amino acids are attached to each other in long chains to form a protein
2. PROTEINS
• The Molecules which yields amino acids upon
hydrolysis are called proteins.
• Proteins are natural polymer of amino acids.
• The number of amino acids in a protein
molecule may range from two toseveral
thousands.
• Protein molecules contain Nitrogen,Carbon,
Hydrogen andOxygen.
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3. PROTEINS
• Proteinsare the basis for the major structural
components of animal and human tissue.
• They act as biological catalysts (Enzymes),
form structural parts of organisms,participate
in different cell reactions, act as molecules of
immunity and also providefuel.
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4. SOLUBILIY
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•Soluble in water, eg., Albumin,histones etc
•Soluble in 70-80 % alcohol, eg.,Gliadin
•Soluble in dilute salt solution, eg., Globulins,(
serum,milk etc)
•Insoluble protein, eg., Scleroprotein (
collagen,keratin etc)
5. CLASSIFICATION OF PROTEINS
(a) Simple Proteins
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• Those which give one amino acid only upon
hydrolysis.
(b) Conjugated Proteins
• Those which give an amino acid and a non-protein
group upon hydrolysis..
(c) Derived Proteins
• Those which are derived from simple and conjugated
proteins.
7. STRUCTURE OF PROTEINS
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• Depends upon the spatial arrangement of
polypeptide chains.
• Three arrangements are possible.
• Four structures:
i. Primary structure
ii. Secondary structure
iii. Tertiary Structure
iv. Quaternary Structure
8. The Primary Structure OfProteins
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• The sequence of amino acids in a
polypeptide chain is called a primary
structure.
• AminoAcids are linked with one another
through peptide bonds.
10. The Secondary Structure Of Proteins
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• Peptide chains may acquire spiral shape
or may be present in a zig zig manner.
• This coiling of peptide chains is called the
secondary structure ofproteins.
• It is due to Hydrogen bonding.
12. The Tertiary Structure OfProteins
• Twisting or folding
of polypeptide
chains represents
tertiary structureof
proteins.
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13. The Quaternary Structure Of Proteins
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• Quaternary means four.
• It is the arrangement of multiple folded
protein or coiling protein molecules in a
multi-subunit complex.
• A variety of bonding interactions including
Hydrogen bonding, salt bridges and
disulfide bonds holds the various chains
into a particular geometry.
16. Denaturation
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The process that changes the shape of a protein
molecule without breaking its peptide bonds.
Denaturation breaks the hydrogen bonds that
create the twists and turns of a protein molecule
17. Properties Of Proteins
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• Found in all livingorganisms.
• Involved in processes such as digestion of
food, cell structure, catalysis, movement,
energy manipulation etc.
• Complex molecules.
• Polymers of amino acids.
• Long chains of amino acids are called
Polypeptides.
18. Importance of Proteins
• Proteins play an important role in
formation of protoplasm.
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19. Importance of Proteins
• Nucleoproteins are
complex proteins and
act as the carrier of
heredity materials from
one generation to
another.
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20. Importance of Proteins
• Enzymes are the biological catalyst and
they are also proteins
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24. Biuret test – general test for detecting the presence of
peptide bond.
• Named after the compound, biuret
• reagents: cuso4 solution and dilute naoh
•Positive result: formation of pink to violet to blue
color
• principle: complexation of cu+2 with amide N atoms
.
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25. Ninhydrin test – general test for detect ammonia or primary
and secondry amines.
• One of the most sensitive color reactions known
• Reagent/s: ninhydrin (1,2,3 - indanetrione monohydrate) in
ethanol
• positive result: blue to blue violet color
•Principle: oxidative deamination and decarboxylation;
reduction of ninhydrin
•Proline, hydroxyproline, and 2-, 3-, and 4-aminobenzoic acids
fail to give a blue color but produce a yellow color instead
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26. Xanthoproteic test – general test for aromatic amino
acids such as tryptophan, phenylalanine, histidine and
tyrosine.
• Presence of electron donating substituents enhances reaction
rate.
• Reagents: conc. HNO3 and conc. Naoh (neutralize excess acid).
•Positive results: formation of yellow precipitate and after
addition of excess naoh (alkaline), an orange precipitate forms.
•Principle involved: nitration of aromatic rings (i.E. Indole in
tryptophan!) Via electrophilic aromatic substitution.
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27. Sakaguchi test – specific for arginine(guanido
group)
•Reagents:-napthol, naoh and naobr (and urea to
stabilize color and destroy excess obr-anions).
• Positive result: red to red-orange color.
•Principle: base-catalyzed condensation of
napthol with the guanido group of arginine.
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