This document discusses proteins, their structure and functions. It covers the following key points: 1. Proteins are made of amino acids bonded together by peptide bonds. Their structure involves primary, secondary, tertiary and sometimes quaternary levels. Secondary structure includes alpha helices and beta sheets formed by hydrogen bonding. 2. Proteins have many important biochemical roles such as enzymes, hormones, antibodies, and structural components. Diseases can result from protein deficiencies or metabolic disorders affecting amino acid breakdown. 3. Protein structure can be disrupted through denaturation which unfolds secondary and tertiary levels, though the primary structure is maintained. Some examples of related diseases include phenylketonuria and maple syrup urine

1. Proteins & their
Biochemical Role
Ms. Shalini N. Barad
Associate Professor
Appasaheb Birnale College of Pharmacy

2. 1. Covalent Interaction:
a)Peptide bond
b)Disulphide bond
2. Non covalent bond
a)Hydrogen bond
b)Ionic bond
c)Hydrophobic bonds

3. a) Peptide bond:
AA in protein are joined by peptide bond.
The Alpha carboxyl & alpha amino group of
different amino acid codense together to form
peptide bond
During this reaction H2O (water ) molecule is
removed.

4. b) Disulphide bond:
-Disulphide bond are formed by covalent interaction
of the sulpha hydril (-SH) group of two cysteine
residues of a peptide.
-The disulphide chain may be interchain or intrachain.

6. 2. Non-Covalent Interaction:
⚫ These are required for the building up of a protein
structure.
a) Hydrogen bond: The oxygen atom of a carbonyl,
hydroxyl, & carboxyl group forms weak electrostatic
bond with the hydrogen atom of an amide or amino
group

8. b) Ionic Bond:

9. c) Hydrophobic bonds:
- Non polar amino acid shoe this type of
interaction.
- Non polar amino acid come close to each
other & form a bond.
-This interaction take place in the inner
region of the protein.

10. • Protein:
• Proteins are naturally occurring nitrogen
containing complex substance that consist of large
number of α amino acid residues joined by peptide
linkage (CO-NH) found in all living system.
• Function:
1. Some proteins act as hormones and hence regulate various
metabolic process e.g. insulin is responsible for
maintaining blood sugar level, hormones receptor, etc.
2. Some proteins act as catalyst for biological reaction.
3. Nucleoproteins act as carrier of genetic characters.
4. Proteins are responsible for transportation of metabolite or
gases (like oxygen, CO2
) are called transport protein.

11. 5. Some blood proteins help to form antibodies
which provide resistance to disease so called as
antibodies or defense proteins.
6. Protein Which are required to give strength to cell
or tissues called structural protein viz collagen in
connective tissue, keratin in hair.
7. Protein which are required to carry out
mechanical work are called muscle protein. ]
8. Plasma protein maintains blood volume.
9. Protein like thrombin, fibrogen, & other protein
factor are involved in blood coagulation.
10. Various proteins forms complement system &
other protein factors are involved in blood
coagulation.

12. Classification of Protein

13. A) According to their shape:
i)Fibrous protein
ii)Globular protein
B) According to their chemical nature/
Composition
i)Simple protein
1. Protamines
2. Histones
3. Albumins
4. Globolins
5. Epidermal protein
6. Scleroprotein

14. Ii) Conjugated protein:
1. Nucleoprotein
2. Chromoprotein
3. Phosphoprotein
4. Glycoprotein
5. Lipoprotein
6. Lipoprotein
7. Metalloprotein

15. A) According to their shape:
i)Fibrous protein:
They are long fibers of linear molecules that are
arranged parallel to fiber axis.
They are insoluble in water.
Eg: Hair, Nail, Bones, Horns, etc
ii)Globular protein:
They are spherical or ovoid in shape.
They are highly branched & cross linked in
structure.
They are soluble in water.
Eg: Hormones, Haemogobin

16. B) According to their chemical nature/
Composition
i)Simple protein:
These contain only amino acid residues & no other intimately
bound material.
They are further classified according to solubility:
1) Protamines: they are very basic low molecular weight (3000 to
10000). They contain high proportion of arginine. They are not
heat coagulable.
2) Histones: They are basic proteinwith high molecular weight
than protamin, & have high contain of arginie, lysine, &
histidine. They are heat coagulable.

17. 3.Albumin & globulin: These are globular protein.
Found in all cells. These class includes the
plasma protein, enzymes & hormones
4. Epidemal protein: these are the protein of the
skin, hair, nails have a high cystein content. They
have cross linking of polypeptide chain by s-s-
bridges.
• 5) Scleroprotein:
these are coonective protein such as collagen,
elastin , etc

18. • Ii) Conjugated protein:
• These contain in addition to polypeptide chains,
other substances or group which impart
characteristic properties. These non amino acis
components are called as prosthetic groups. These
include:
1)Nucleoprotein: these are formed by combination
of histone or protamine with ribonucleic acid or
deoxyribonucleic acid.
2) Chromoprotein: they are generally soluble
proteins combined with chromophoric (coloured )
group.
• This group is haem (haemoglobin) , Riboflavin
(flavoprotein)

19. 3)Glycoprotein: These consist of amino sugars,
sugar acid & sulphate
4)Lipoprotein : it is the combination of protein &
lipids.
• These are found in cell membrane, plasma, brain
5) Phosphoprotein:
They are either ortho or pyro phosphate or
phosphodiesters. Eg: milk casein is a globulin
protein containing about 1% of phosphorous &
pepsin contain one atom of phosphorous.
5)Metalloprotein:
• Various metals are attached to simple protein

20. C) Derived Proteins: Contain products obtained on
hydrolysis of simple & conjugated protein.
⚫ i) Primary derived protein:
-They are the denatured or coagulated or first
hydrolysed products of protein.
⚫ Ii)Secondary derived protein:
-They are degraded (due to breakdown of peptide
bonds) product of proteins.

22. ⚫ Also classified on basis of nutritional value:
1.Incomplete protein: protein not containing all
essential amino acid. Eg: gelatin , zein of maize
2.Complete protein: protein which contain all
essential amino acid in required quantities are
called complete protein . Eg: milk protein & egg
protein.

23. Structure of Proteins
A. Primary structure of Protein
B. Secondary Structure of Protein
C. Tertiary Structure of Protein
D. Quaternary structure of Protein

24. A)Primary Structure of Protein:
⚫ Each protein has the characteristic sequence of amino
acid.
⚫ Primary structure of protein includes the amino acid
sequence which are linked together by peptide bond.
⚫ They are formed by the aa linked by carboxyl group
(-COOH) of one amino acid with amino group of
another amino acid.

27. B) Secondary structure of Protein:
⚫ The secondary structure is formed by hydrogen bonds
between carbonyl and amino groups that make up the
polypeptide backbone and causes the molecule to either
bend and fold (beta pleated sheet) or spiral around
(helicase).
⚫ These folding are essential for functional activity of protein
which are brought about by hydrogen bonding or
disulphide bonding between neighboring amide &
carboxyl group.
⚫ Secondary structure deals with the shape of peptide chain
i.e. linear, cyclic, branched or arranged in the form of helix.
⚫ In protein molecule polypeptide is present in different
geometric arrangement called folding.

28. ⚫ It is essential for the functional activity of the protein.
⚫ Based on nature of hydrogen bonding there are two types:
⚫ (i) α- helix (α- helical)
⚫ (ii) β-pleated sheet
i) α- helix (α- helical)
⚫ The α helical is the most common spiral structure of
protein.
⚫ It has a rigid arrangement of polypeptide chain.
⚫ Each turn coil carries 3.6 aa residue & each aa residue is
placed 0.15nm from the next.
⚫ The α - helical structure depends on the intramolecular
hydrogen bonding between NH and C=0 group of peptide
bond, in the α - helix the polypeptide is folded in such a
way that the C=O of each amino acid residue is hydrogen
bonded to the NH of 4th amino acid residue along the
chain. Eg: Keratin

30. ⚫ (ii) β-pleated sheet: It is another form of
secondary structure, this result from hydrogen
bonding between two peptide chains.
⚫ It may occur in two types
⚫ a) Parallel pleated sheet:
⚫ In this type of structure the polypeptide chain is
side by side and in the same direction so that
N-terminal residues are on the same end.
⚫ This pleated sheet confirmation is stabilized by
hydrogen bonding, here bonds are formed
between NH group of a peptide in one chain and
C=O group of a neighboring chain.

31. ⚫ b) anti- parallel pleated sheet-
⚫ In this type of structure the polypeptide chain lie
in opposite direction so that N-terminal end of one
and C- terminal of the other, face each other.
⚫ In this structure the polypeptide chains are held
together by hydrogen bonds, so as to give a sheet
like structure and hence are called as β –pleated
sheet confirmation.

33. Eg: Silk

34. C) Tertiary structure of Protein:
⚫ It is three dimensional folding of the chain stabilized
by the interaction between distant part of the
sequence.
⚫ Long polypeptide chain is very tightly folded in to a
compact form.
⚫ This folding results from interaction of R groups of
side chain of amino acid.
⚫ The interaction are : a)Hydrogen bonds
b) Hydrophobic bonds
c) Ionic bonds

35. D)Quaternary Structure of protein:
⚫ The protein which contain two or more polypeptides
held together by non-covalent interaction.
⚫ They are called quaternary protein.
⚫ Eg: Haemoglobin (it contain 2α & 2β polypeptide
chain)

36. ⚫ Peptides
⚫ A peptide is the condensation product of two or more
aa; wherein two aa , the α amino group of one amino
acid is condensed with the α carboxyl group of the
another.
⚫ Eg: Condensation of Glycine with alanine
Glycylalanine (dipeptide)

37. ⚫ Polypeptide: These are the compounds which contain
20 to 50 amino acid.
⚫ Biological importance of peptide & polypeptide:
1. Insulin is a peptide which plays an important role in
glucose metabolism.
2. Valinomycin & gramicidin are peptides useful as
antibiotics.
3. Bleomycin, a peptide is antitumor agent.
4. Bradykinin is a polypeptide used as smooth muscle
hypotensive agent.

38. ⚫ Denaturation of Protein:
The disruption of native structure of protein which causes changes in
properties of protein & loss of biological activity is called as
Denaturation of protein.
Denaturation of proteins involves the disruption and possible
destruction of both the secondary and tertiary structures.
Since denaturation reactions are not strong enough to break the peptide
bonds, the primary structure remains the same after a denaturation
process.
Agents causing denaturation
1. Physical agents: Temperature, Cooling
2. Chemical gents: Acetic acid, Sulfosalicyclic acid, X ray, Organic
solvents
Changes after denaturation
a)  Loss of biological activity
b)  Change in surface tension
c)  Changes in solubility
d)  Destruction of secondary and tertiary structures
• E.g . Boiled eggs become hard, skin formed on curdled milk

39. ⚫ Protein related Diseases:
1) Protein deficiency disease
2)Protein metabolic disorder
1) Protein deficiency diseases:
a) Marasmus- Seen in infants
b) Kwashiorkar- Seen in children between the ages of 1-4yrs
c) Nutritional Edema- Seen in elders
a)Marasmus
1. Deficiency disease of infants below 1 year
2. More likely to occur in poor people
3. Most important cause is early stoppage of breast feeding
Symptoms: Results in growth retardation, muscle wasting,
anaemia, hair pigmentation, vomiting & diarrhoea.
1. No edema observed

40. • Treatment:
1. Mother’s milk,
2. Diet rich in calories, proteins & other nutritional factors.
b) Kwashiorkar:
⚫ The qualitative & quantitative deficiency of protein result
in the disease.
• Predominantly found in children between 1-4 years of age
Causes:
1. Large family size,
2. poor maternal health,
3. over diluted milk,
4. Delayed supplementary feeding
5. Premature termination of breast feeding

41. Symptoms:
1. Retarded growth,
2. edema,
3. alterations in skin,
4. hair pigmentation
5. liver enlargement,
6. vomiting,
7. diarrhea,
8. moon face

42. • Treatment: diet rich in proteins, milk, eggs,
soyabeans (richest source of complete protein)
c)Nutritional edema:
• Usually seen in famine areas
• Results from long, continued deprivation of
proteins
• Symptoms: Weight loss, reduced subcutaneous
fat, anemia, greater susceptibility to infections,
frequent loose stools, lethargy, edema.
• Treatment: Protein rich diet, milk, eggs, soyabean

43. 2.Protein metabolis disorder:
A) Phenylketonuria:
⚫ The disease or inborn error of metabolism which
result due to absence of phenylalanine hydroxylase
which convert phenylalanine Tyrosine is
called as phenylketouria.
⚫ So their will be accumulation of phenylalanine in
body fluid.
⚫ Due to this their will be alternate pathway of
phenylalanine which forms phenylpyruvate,
phenylacetate, phenylactate.
⚫ All these alternate products are excreted in urine

44. ⚫ Symptoms:
1. Mental retardation
2. Seizures
3. Psychosis
4. Eczema
⚫ Treatment:
1. Early diagnosis after birth
2. Strict intake of phenylalanine is effective preventive
measures

45. B) Alkaptonuria:
⚫ The inherited metabolic disorder found in infant
which result due to absence of an enzyme
homogentisate 1,2-dioxygenase is called as
alkaptonuria.
⚫ Homogentisate 1,2-dioxygenase is responsible for
the breakdown of homogentisate an intermediate
in phenylalanine & tyrosine pathway.
⚫ It causes accumulation of homogentisate as it
breakdown is blocked & is excreted in urine.
⚫ Due to this urine becomes black on standing
because of oxidation of homogentisate with air.

46. c)Maple syrup urine disease:
⚫ It is called as branched chain ketoaciduria.
⚫ The diseases which is caused due to absence or highly
reduced activity of branched chain
α-ketodehydrogenase complex is called as Maple syrup
urine disease.
⚫ The enzyme α-ketoacid dehydrogenase coplex
catalyses conversion of 3 branched chain amino acid.
Eg: leucine, isoleucine, valine.
⚫ As a result these amino acid accumulate in the blood &
excrete in urine.

47. ⚫ Symptoms:
1. Burnt sugar odour of urine
2. Difficult to feed
3. Vomiting
4. Lethargy, extensive brain damage.
⚫ Treatment:
1. This disease is usually fatal, patient is placed on diet in
which protein is supplied by a mixture of amino acid
except leucine, isoleucine, & valine

48. Imp Questions
1.Enlist structure of protein? Explain secondary structure
of protein?
2.Enlist protein deficiency disease & explain Maple
syrup urine disease?
3.Explain Phenylketonurea metabolic Disorder?
4. Explain denaturation of protein?
5. Define protein & give its classification?
6. Define protein & give its biological function/ Role?
7. Draw the structure of following amino acid:
⚫ i) essential amino acid(any four)
⚫ Ii)optically inactive amino acid

49. ⚫ Iii)sulphur containing amino acid
⚫ Iv) Aromatic amino acid
⚫ V)acidic amino acid
⚫ vI)basic amino acid
⚫ Vii)polar amino acid (any four)
⚫ Viii)hydroxyl group containg amino acid
8. Explain the following test: ninhydrin test
FNDB test, Dansyl test, Pheylisothiocynate test,
Xanthoproteic test, glcoxylic test, Sakaguchi test

50. 9. Explain acid base behavior of amino acid/ isoelectric
pH/ Zwitter ion ?
10.Write a note on Protein deficiency disease.