The document discusses the classification, structure, and functions of proteins. It describes 8 types of proteins based on their functions, including structural, catalytic, transport, hormonal, gene regulatory, protective, receptor, and contractile proteins. It also discusses the primary, secondary, tertiary, and quaternary structure of proteins, as well as their denaturation. Finally, it outlines several important functions of proteins such as providing energy, structure, defense, transport, catalysis, and storage of genetic information.

1. AminoAcidsandProteins
Part:2
9/6/2022 Dept of Biochemistry, SSMC 1

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LearningObjectives
 Classificationofproteins
 Sourcesofproteins
 Propertiesofproteins: Isoelectric pH
 Differentstructuresofproteins
 Denaturationofproteins
 Functionsofproteins

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Types Function Example Types Function Example
i)
Structural
Protein
Support
framework
of cell
Collagen, Elastin,
etc
v) Gene
regulatory
Protein
Regulate
genetic
functions
Histone,
Protamine
ii)
Catalytic
Protein
Catalysis Enzymes vi)
Protective
Protein
Prevent
infection
Immunoglobulin
iii)
Transport
Protein
Transport
of
substances
Albumin,
Transferrin
vii) Receptor
Protein
Receptor
function
LDL receptor
iv)
Hormonal
Protein
Regulation
of
functions
Insulin, Glucagon viii)
Contractile
Protein
Muscle
contraction
Actin, Myosin
A) FunctionalClassificationofProteins

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Points i) Simple protein ii) Conjugated
protein
iii) Derived
protein
Composition Composed of amino acid
residues without
any non protein
substances
Composed of protein
along
with non protein
prosthetic substances
Denatured /
degraded
products of
simple protein &
conjugated
protein
On
hydrolysis
They produce only amino
acids
They produce amino acid
plus other non amino
acid substances
-
Types 2 types: Fibrous protein &
Globular protein
- -
Example Fibrous: Collagen, elastin,
keratin etc
Nucleoprotein,
lipoprotein
Proteose, peptone,
PP,
B) Classificationofproteinsbasedontheirsize,shape&solubility

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Points Fibrous protein Globular protein
Synonym Scleroprotein Spheroprotein
Shape Fibre like with high tensile
strength
Oval / spherical
MW High Relatively low
Origin Entirely animal origin -
Water
solubility
Insoluble Soluble
Digestibility Highlyresistanttoproteolyticenzymes Digestible by proteolytic
enzymes
Site Tendons, ligaments, cartilage, hair,
nail
etc
-
Example Collagen, elastin, keratin etc Albumin, globulin, histone,
protamine etc

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Conjugated protein Prosthetic / Non protein
groups
Nucleoprotein Nucleic acid (DNA , RNA)
Lipoprotein Lipid
Glycoprotein Carbohydrate (oligosaccharide)
Hemoglobin, myoglobin,
peroxidase, catalase,
cytochrome
Heme
Ferritin Iron
Ceruloplasmin Copper
Carbonic anhydrase Zinc

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Points i) Complete
protein
ii) Incomplete
protein
iii) Partially
incomplete
protein
Composition Containsall essential
amino acids
Completely lack one or
more essential
amino acids
Partially lack one or
more essential
amino acids
Role on
growth
Promotes growth Can not promote
growth
-
Example Egg albumin, meat etc Gelatin (lacks Trp) Wheat protein
C) Nutritionalclassificationofproteins

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12. PhysicalProperties
 Macromolecule
 Shape: variable
 MW:Variable
 Showsdifferential solubilitybut
mostlywater insoluble
 Formscolloidal solutionwithwater
whichis opticallyactive
Chemical Properties
 Amphoteric /Ampholyteinnature
 Actsasbuffer
 Heat labile (Denatured /coagulated by
heat)
 Expresseschargeonthesurface
 Have adefiniteiso-electric pH
 Givescolourreactionwith
 ninhydrinreagent
 biuretreagent
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13. ProteinsexistasZwitterion/Dipolarform atisoelectric pH
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Isoelectricpoint(pI)/Isoelectric pH:
It is thepH ofanaqueoussolutionofanaminoacid (or protein) atwhich the
moleculesonaveragehavenonetcharge.

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15.  Usually describedat4levels
oforganization
 Anyalterationinthe
structureor sequencing,will
changetheproperties and
functionsoftheprotein
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17.  Exact linear sequenceofaminoacidsinaproteinheldtogetherbypeptidebonds
 Each Aminoacidinapolypeptidechainistermedasaminoacidresidue
 N-terminal end/Aminoend: ThefreeNH2 group ofoneterminal aminoacid,
traditionallyassumedtobeonlefthandsideofaPP chain
 C-terminalend/Carboxylend:ThefreeCOOH groupofanotherterminalaminoacid,
traditionallyassumedtobeonright handsideofaPP chain
 Sequenceofaminoacidsis writtenfromN-terminus tothe C-terminus
A) PrimaryStructure
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18.  Primarystructureofaproteinis
determinedgenetically andthis
inturn determinesthesecondary,
tertiary& quaternary structure
of thatprotein
 Anychangeinthesequenceof
aminoacids inapeptide/PP
chainisabnormal & mayaffect
thepropertiesandfunctions of
theprotein
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19. Why calledAminoacidresidue?
Because, aminoacidsinthepeptide/polypeptidechains havealready
lost theatomsof waterduring
formationofpeptidebonds amongthem
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20. B) SecondaryStructure:Formedbyperiodicfolding,twistingorcoilingofits
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primarystructure
HelicalStructure:
It is produced likea
spiral staircase
aroundthecentral
axis.
Pleatedsheet:
It is formedby
hydrogenbond
between2extended
polypeptidechains

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22. D) QuaternaryStructure
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C) TertiaryStructure

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Points A) Primary
structure
B)
Secondary
structure
C) Tertiary
structure
D) Quaternary
structure
What is
it?
Exact linear
sequence of
amino acids in
a protein held
together by
peptide bonds
The Helical or
pleated
sheet like
protein
The three
dimensional
globular form of
protein
A multi chain oligomeric
protein
How
formed?
By joining a
number of
amino acids
whose
sequence is
determined
genetically
By periodic
folding,
twisting or
coiling of its
primary
structure
By further folding &
twisting of a
secondary
structure of protein
about itself keeping
the hydrophobic
side chains buried
interiorly &
By joining of 2 or more
polypeptide chains
(same / different
type) at a definite
spatial relationship.
(Individual PP chain is
called monomer/
subunit)

24. Points A) Primary
structure
B) Secondary
structure
C) Tertiary
structure
D) Quaternary
structure
Any
specialty?
It determines
the
secondary,
tertiary &
quaternary
structure of
a specific
protein
2 types of
conformation:
i)Helical form
ii)Pleated sheet
form
It is the overall
shape
of a single protein
unit.
The protein is
functionally
active at this
level
Collection of single
protein units at
tertiary
level.
Specific
Bond (S)
- Peptide bond
(Mainly)
- Di sulfide
bond
- Peptide bond
- Di sulfide bond
- Hydrogen bond
- Peptide bond
- Di sulfide bond
- Hydrogen bond
- Ionic bond
- Hydrophobic
bonds
- Van der walls
Same as tertiary
structure :
- Peptide bond
- Di sulfide bond
- Hydrogen bond
- Ionic bond
- Hydrophobic

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Points Primary
structure
Secondary
structure
Tertiary
structure
Quaternary
structure
Example Insulin Fibrous protein
(collagen, elastin,
keratin)
Albumin, globulin,
antibody etc.
Hb, Insulin, CPK,
LDH etc

26. Disulfidebond:
(–S–S–) formedbythecouplingoftwothiol (–SH) groups.
Cysteinehasthiol groupinitssidechain.
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29.  It istheprocessof disruption&
possibledestructionof of protein’s
secondary,tertiary& quaternary
structureswhilepreservingthe
primary structure.
 It isnotaccompaniedbyhydrolysis
ofpeptidebond.
 Nointramolecularchange(no
changeinMW)
 Changeoccursinpropertiesof
proteins
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30. Denaturation
Usually Irreversible
(e.g.Boiledegg,cooked
meat/fishetc)
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Reversible
(Underideal condition.
e.g.Ribonucleaseathighurea
conc.)

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Denaturingagents:
 Physicalagent:Extremesoftemperature,
ultrasound,UV radiationetc
 Chemical agents: ExtremepH,strongacid/
alkali, detergent, heavymetalsetc

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Changesinproteinfollowingdenaturation
 Physical change:
 Increasedviscosity
Decreaseddiffusibility
 Chemical change:
 Increasedchanceofprecipitation
 Decreasedsolubility
 Biologicalchange:
 Lossoffunction
Increaseddigestibilitybyproteolyticenzymes

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 Sourceofenergy
 Formationofcytoskeleton
(Flexiblestructural
framework for cells/tissues)
 Provides:
Mechanicalsupport: By structural protein
likecollagen, elastin
Defenseagainst infection: By antibody like
immunoglobulin
 Helpsin:
Musclecontraction: By
contractileprotein likeactin,
myosin
 Coagulation: By clottingfactors
 Actsas:
Vehicle for transport of diff
molecules likehormones,drugs, vitamins
etc
 Buffer

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 Promotes:
 Catalytic functionbyenzymes
 Hormonalfunctionsbyhormones
 PlasmaproteinsmaintainCOP of
plasmatomaintainbloodvolume
 Storage,expression& transmissionofgeneticinformationby
nucleoprotein