Classification based upon i- Chemical Composition ii-Function iii-Size iv-Shape v-Nutrition

1. Hafiz Muhammad Umair
Institute of Chemistry
UNIVERSITY OF SARGODHA
1

2.  Proteins are the most abundant organic compounds of Living systems.
 occur in every part of the cell and constitute 50% of dry weight of cellular
weight.
 The word proteins are derived from Greek word Proteios meaning
Holding First Place.
 Proteins form the fundamental basis of structure and function of life.
 Proteins perform a great variety of specialized and essential functions in
living cells.
 These functions may be broadly grouped as:
o static (Structural) and
o dynamic.
 The main objective of this statement of proposes to explain and verify
different classification types on the basis of Properties, shape, size, value
of use in daily life and in body.
2

3.  The Proteins are second most abundant bio molecules in
the nature
 The most abundant protein in nature is probably the
chloroplast enzyme ribulose bisphosphate
carboxylase/oxygenase (Fraction I protein). An enzyme
 Carbohydrates, the most abundant biomolecule on
earth, are produced by All of Five Kingdoms
 Collagen is the most abundant structural protein in the
extracellular matrix of the human body as well as in
other animals
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4. 4
• Bio molecules, Organic Compounds
• Polymers of Amino acids joined by Polypeptide Bonds Between
hydroxyl and Amine group
• Containing C,H,N,O and P,S

5. 5

6. Protein classification based on chemical composition
 It is the most popular classification. Based on
 Amino acid Composition
 Structure
 Shape & Solubility
 There are three main types Simple, compound and derived proteins.
 Simple Proteins
 Conjugated Proteins
 Derived Proteins
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7. Types Based on
Chemical composition
Simple Proteins
Conjugated Proteins
Derived Proteins
7

8. Simple Proteins
Albumins
Globulins
Albuminoids
Globin
Histones
Prolamins
Protamine
Glutelin
Digestible
May basic or Not
They are spherical in shape
Soluble in water and other solvents in different concentrations.
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9. Simple Proteins
A
Albumins
• Globular proteins, the most common of which are
the serum albumins.
• found in blood plasma and differ from other blood
proteins in that they are not glycosylated.
• blood transport proteins are evolutionarily related in the
albumin family, including serum albumin, alpha-
fetoprotein, vitamin D-binding protein and afamin.
• This family is only found in vertebrates.[
• Soluble in water, Heat Coagulated, Precipitated at full
saturation
E.g. Serum Albumin, Oval albumin, lactalbumin
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10. 10
Structure of Albumin
 consisting of a single chain
of 585 amino acids
 AAs contains three Homolog
domains (sites I, II, and III).
 Each domain comprises two
separate sub-domains (A and B)
 The Single chain is Alpha helix.

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G
Globulins
 Group of proteins in blood.
 Made in liver by immune system.
 Globulins play an important role in liver function,
blood clotting, and fighting infection.
 There are four main types of globulins. They are
called alpha 1, alpha 2, beta, and gamma.
 Soluble in water & in dilute Solutions
 Coagulated by heat, Precipitated at half saturation
 E.g. Serum Globulins, Oval globulins,
Lactoglobulins, Legumin of Pea
Simple Proteins

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Globulin Types
α1 Globulins
Transport of Lipid, Thyroxin, Corticosteroid Harmons
α2 Globulins
Transport of lipids , Copper Ions
β Globulins
Transport of lipids, Iron and Precipitation of β-Globulins in immune
system as Antitoxins
γ Globulins
As immunoglobulins functions

13. Simple Proteins
A
Albuminoids /Scleroproteins
• One of the three main classification of protein
structure (alongside globular and membrane proteins)
• Made up by elongated or fibrous polypeptide chains which form
filamentous and sheet like structure.
• Protection and structural role by forming connective
tissue, tendons, bone matrices, and muscle fiber.
• Insoluble in water, salt solution, acid and alkali, Not coagulated by
heat, not precipitated
• E.g. superfamilies Like Collagen, keratin and Elastin
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Made up of three polypeptide strands, each of which is a left-handed helix
• Helices are twisted together into a right-handed coiled coil, a triple helix
• Triple helix is stabilized by H-bonding
• There is some covalent cross-linking within the triple helices
• Rich in Glycine, Proline, Hydroxyproline Non Alpha helix
Structure of Scleroprotein

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Globin
• Heme-containing globular proteins, involved in binding oxygen
• Three-dimensional 'globin fold’, typically of eight alpha helices
• Fold contains only helices, it is classified as an all-alpha protein fold.
• Helix bundle packs together at an angle of about 50 degrees
• Helix packing angle depends on the sequence of the protein,
steric and hydrophobic interactions of the amino acid side chains near
the helix interfaces.
• Soluble in water, Dilute acid and Alkali, Soluble in neutral salt
solution
• Not coagulated by heat, Basic protein
• e.g.. Globin of Hemoglobin and Myoglobin
G
Simple Proteins

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Structure of Globin
• Made up of 4 polypeptide chains
• 2 alpha chains
with 141 AAs(55% alpha helix)
• 2 beta chains
with 146 AAs(45% beta helix)
HbA1 have total 574 AAs
• 4 subunits of hemoglobin are held by
Non covalent, Hydrophobic, ionic &
H-bonding
• Each subunit contains a Heme group

17. Simple Proteins
H
Histones
 Highly basic proteins (abundant in lysine and arginine)found
in eukaryotic cell nuclei that pack and order the DNA into
structural units called nucleosomes
 Histones are the chief protein components of chromatin
 Five major families of histones exist: H1/H5, H2A, H2B, H3,
and H4.Histones H2A, H2B, H3 and H4 are known as the
core histones, while histones H1/H5 are known as the linker
histones.
 Soluble in water, Mainly found in association with Nucleic
acid and gives stability to genetic material, Not coagulated
 e.g. Histones of nucleoproteins, Thymus
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Bead of Nucleosome
Consist of Eight Histones proteins which are in
paired(Above & Below) form and linked and joined
by the Linker Proteins H1/H5

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Protamine
 Small, Simplest of the proteins, arginine & lysine-
rich, nuclear proteins
 Replace histones late in the haploid phase of spermatogenesis and are
essential for sperm head condensation and DNA stabilization.
 Helps in denser packaging of DNA in the spermatozoon than histones
 During sperm formation, protamine binds to DNA backbone using the
arginine-rich domain. DNA is then folded into a toroid, an O-shaped
structure, although the mechanism is not known.
 Soluble in water, Dilute acid and alkalis. Not coagulated by Heat and.
 e.g. Zinc Insulin ate, Nucleon protein of sperm, Saline
P
Simple Proteins
Toroid:
Toroid are small donut shaped organizational
units within sperm chromatin and viruses
containing DNA and protein

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Protamine P1, the protamine used for packaging DNA in sperm cells, it is usually 49 or
50 amino acids long.
This sequence is divided into three separate domains
Protamine has a key role in spermatozoa chromatin condensation. Its
deficiency causes negative effects on morphology and male fertility

21. Simple Proteins
Prolamin
Plant storage
proteins having a
high proline amino acid
content. They are found in
plants, mainly in the seeds
of cereal grains
Insoluble in water,
Soluble in dilute alcohol,
Not Coagulated by Heat
e.g. Proline rich proteins
of plants deficient in
Lysine
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Glutelin
 Class of prolamin proteins found in the endosperm of certain seeds of
the grass family.
 They constitute of the protein gluten. Glutenin is the most common
glutelin, found in wheat.
 Responsible for some of the refined baking properties in bread wheat.
 The glutelin's of barley and rye have also been identified.
 Glutelin's are the primary form of energy storage in the endosperm
of rice grains.
 Insoluble in water, Soluble in salt solutions, Coagulated by heat,
Found in Plants
 e.g. Zein of maze/Corn, Gliadin of wheat
Simple Proteins

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What is Gluten

24. Conjugated Proteins
Polypeptides with Prosthetic group i.e. Non Proteinic Part
Glycoproteins Lipoproteins
Phosphoproteins Nucleoproteins
Chromoproteins Metalloproteins
Flavoproteins
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25. Conjugated Proteins
Glycoproteins
Carbohydrates as Prosthetic group like mucopolysaccharides, which include hyaluronic
acid and chondroitin sulphates with the process of Glycosylation.
 In N-glycosylation, With nitrogen, (in asparagine.
 In O-glycosylation, with oxygen, (in serine or threonine).
 In P-glycosylation, With phosphorus on a phosphoserine.
 In C-glycosylation, with carbon, (as in the addition of mannose to tryptophan.)
 In S-glycosylation, With sulfur atom of a cysteine residue.
 In glycation, also known as non-enzymatic glycosylation, sugars are covalently bonded to a
protein or lipid molecule, without the controlling action of an enzyme, by Maillard reaction.
Not readily denatured by heat nor easily precipitated by common protein precipitants. e.g.
Mucoproteins, Blood Group Antigen,ovomucoid from egg white, Cell Membrane
Receptors
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*Mucopolysaccharides are long linear polysaccharides consisting of repeating
disaccharide units. The repeating two-sugar unit consists of a uranic sugar and an amino
sugar,

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Glycoproteins
 Glycoproteins plays a
fundamental function in the
Skeletal formation of Cell
membrane
 They are involved in many
physiological functions
including immunity
 They can be used in different
forms of communication
between cells. Glycoproteins in
the cell membrane are very
important for cell-to-
cell recognition and adhesion,
 They serve as receptors for other
types of molecules.

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Phosphoproteins (Phosphorylation)
Protein phosphorylation is extremely important in
 protein synthesis,
 cell division,
 signal transduction,
 cell growth,
 development and aging as many enzymes and
 receptors are activated and deactivated via
 phosphorylation/dephosphorylation events due to specific kinases and phosphatases
Proteins Containing Phosphoric acid as prosthetic group.
Phosphoric acid is linked to the hydroxyl group of certain amino acids like serine in the
protein
e.g., casein of milk.
Conjugated Proteins

28. Conjugated Proteins
Lipoproteins
 Lipoproteins transport hydrophobic lipid (also known as fat) molecules
in water, as in blood plasma or other extracellular fluids. They consist of
a Triglyceride and Cholesterol center.
 Containing two portions
 Hydrophilic (Outward)
 Hydrophobic/Lipophilic (Inward)
 Lipids as prosthetic group.
 E.g. neutral fat, phospholipids and cholesterol
 Many enzymes, transporters, structural proteins, antigens, adhesins,
and toxins are lipoproteins.
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 The hydrophilic head of the
‘’Phospholipid’’ is outward from the
center. While Hydrophobic or
Lipophilic tail is inward or towards the
center.
 Functions:
 lipoproteins help in transport of lipid
to cells and tissues
 Lipoproteins also affect cellular
metabolism in two other ways: they help
maintain a normal cell membrane lipid
composition and they regulate
certain cellular processes
 Cholesterol delivery
 Dietary far delivery

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Proteins that are structurally associated with nucleic
acids, either DNA or RNA.
Typical nucleoproteins include ribosomes, nucleosomes and
viral nucleocapsid proteins.
They are positively charged having interaction to negative ones
Importance
• Carries and transfer Inherited traits
• Responsible for synthesis of Proteins
• Would be helpful in Cancer treatment (Under trails)
• Important vectors in Biotechnology
• Memory is related to formation of RNA in the brain
Nucleoproteins
Conjugated Proteins

31. Conjugated Proteins
Chromoproteins
Flavoproteins
A colored prosthetic group is associated to proteins. It imparts colors to
proteins.
Hemoglobin, Myoglobin and Cytochrome
Riboflavin (Vitamin B2) in association with proteins
e.g. Riboflavin, Flavonoids of Liver and Kidney
Metalloproteins
Metals ions as prosthetic group with proteins. Metal ions activates the
enzyme proteins
e.g. Zinc insulate, Tyrosinase and Carbonic anhydrase
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32. Derived Proteins
Products obtained by hydrolysis, Degradation or Denaturation of Simple/Conjugated Proteins
Primary
Derived Proteins
Secondary
Derived Proteins
Proteins
Meta Proteins
Coagulated Proteins
Proteose
Peptones
Peptides
The complete hydrolytic
decomposition of the
natural protein molecule
into amino acids generally
progresses through
successive stages as
follows:
Protein ----->Protean ------
>Metaprotein Proteoses ---
>Peptones ------->Peptides
------>amino acids
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33. Primary Derived Proteins
These protein derivatives are formed by processes causing only slight
changes in the protein molecule and its properties. There is little or no
hydrolytic cleavage of peptide bonds.
Proteins
insoluble products formed by the action of water, dilute acids and enzymes.
formed from globulins but are insoluble in dilute salt solutions
e.g. myosin from myosin, fibrin from fibrinogen.
Metaprotein
Formed by the action of acids and alkalis upon protein. insoluble in neutral solvents.
Coagulated Proteins
insoluble products formed by the action of heat or alcohol on natural proteins
e.g., cooked meat and cooked albumin.
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34. Primary Derived Proteins
Proteoses
Hydrolytic products of proteins, which are soluble in water and are not
coagulated by heat.
Peptones
Hydrolytic products, which have simpler structure than proteoses.
They are soluble in water and are not coagulated by heat.
Peptides
Composed of relatively few amino acids. They are water-soluble and
not coagulated by heat.
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35. 35

36. Functional
Classification
Catalytic proteins
Exotic proteins
Secretary proteins
Receptor Proteins
Protective proteins Genetic Proteins
Structural proteins
Transport proteins
Storage proteins
Regulation of
Gene Expression
Supportive Proteins
Contractile proteins
Regulatory proteins
Toxic proteins
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37. Functional Classification
Polypeptides and small proteins, play highly important regulatory role in
maintaining order in complex metabolic reactions.
Are involved in the control of many cellular functions, from metabolism
to reproduction. Examples are insulin, glucagon, and thyroid-stimulating
hormone (TSH).
Nucleic Acid (DNA/RNA) are basics for transfer of genetic code and
traits to offspring. They have a prosthetic group of Nucleon-histones and
Nucleoproteins.
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Regulatory Proteins
Genetic Proteins

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works as biocatalyst. Largest class. Nearly 2000 different kinds ,each
catalyzing a different kind of reaction. They enhance the reaction rates a
million-fold
Almost all known enzymes,, are proteins (except some catalytic RNA
molecules called ribozymes, that is, ribonucleic acid enzymes).
Catalytic Proteins

39. Functional Classification
Storage Proteins
 Serve as biological reserves of metal ions and amino acids. They are
found in plant seeds, egg whites, and milk.
 source of essential amino acids, which cannot be synthesized by
human beings.
 e.g. Ferritin a storage protein that stores iron. Iron is a component
of heme, which is contained in the transport protein, hemoglobin and
in cytochromes.
 Some store amino acids, used in embryonic development of animals
or plants. Amino acid storage proteins in animals
are casein and ovalbumin.
 Leguminous plants, contain high concentrations of storage proteins
in sedge's in wheat is the prolamin gliadin, a component of gluten.
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 Proteins that transport substances across biological membranes.
Transport proteins are found in membrane itself in form of channel ,
to allow their substrate to pass from.
 Channel/Pore Carrier Proteins
 Types of transport:
 “facilitated diffusion,” where a transport protein simply creates an
opening for a substance to diffuse down its concentration gradient
 “active transport,” where the cell expends energy in order to move a
substance against its concentration gradient.
 Each transport protein is designed to transport a specific substance as
needed
e.g. Sodium Potassium Pump
 The globin and ferroprotoporphyrin, Helps in oxygen transport
 Myoglobin, a related protein, transports oxygen in muscle
Functional Classification
Transport Proteins

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Na-K pump is an example of Channel/ Pore proteins.
These proteins are characterized by being open to both the intracellular and extracellular space at the same
time.
Channels or pores are typically designed so that only one specific substance can pass through.
The sodium-potassium pump begins with its sodium binding sites facing the inside of the cell. These sites
attract sodium ions and hold onto them. the protein then binds to a molecule of ATP, and splits it into ADP +
a phosphate group. The protein uses the energy released in that process to Export 3Na ions.
Then It takes 2K ions to send them inside.
Due to charge difference electrochemical gradient is formed suitable for passing a nerve impulse

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 Antibodies or immunoglobulins are glycoproteins that
recognize the infectious agents.
Interferon, fibrinogen, and factors of blood coagulation are
members of this group.
 Are produced in the spleen and lymphatic cells in response to
foreign substances called antigen.
 Antibodies are specialized, Y-shaped proteins that bind like a
lock-and-key to the body's foreign invaders — whether they
are viruses, bacteria, fungi or parasites. They are the "search"
battalion of the immune system's search-and-destroy system,
tasked with finding an enemy and marking it for destruction.
Protective Proteins

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Immunoglobulins
 Group of proteins (Gamma globulins) produced by
B-Lymphocytes & Plasma cell in response to an
invader.
 They have 5 basic Isotypes G,M,A,E & D.
 Having similar basic structure
 Structure:
 All of the lgs consist of 4 polypeptide chains
linked by disulfide bonds
 They are Y shaped
 2 heavy chains & 2 light chains due to high and
low molecular weight
 Chains are divided into Variable and constant
regions
 All of them contains ‘Amino terminal’’ at variable
region and ‘’Carboxy terminal’’ at constant region.

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Igs G,A,M,E & D
Name Sub
classes
Function Structure and Identity
IgG 4 IgG provides the majority of antibody-
based immunity against pathogens
Monomeric with Gamma H chain
IgD 1 serves as antigen receptor for the
activation of B cells.
Monomeric with H chain
IgE 1 IgE is bound to tissue cells, especially mast
cells and associated with allergic reactions.
Monomeric with H chain
IgA 2 IgA protects mucosal surfaces by
neutralizing bacterial toxins and inhibiting
adhesion to epithelial cells.
Dimeric with H chain
IgM 1 Produced 1st upon invasion
Increses transienty
Pentameric with µ H chain

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Contractile Proteins
Contractile proteins are proteins that mediate sliding of contractile fibers (contraction)
of a cell’s cytoskeleton, and of cardiac and skeletal muscle.
Muscle fibers consist of bundles of actin polymers that slide alongside each other by
the activity of the motor protein myosin and associated contractile proteins such as
troponin and titin.
Functional Classification

46. Functional Classification
Receptor Proteins
Some of the proteins acts as receptors in livings
Rhodopsin is involved in visuality. I.e. detection of light and image of objects
Acetylcholine is involved in Impulse detection and impulse transfer.
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47. Functional Classification
Structural Proteins
proteins that bind phosphoric acid to serine and threonine residues. Tooth dentin,
milk caseins (alpha, beta, gamma and delta), and egg yolk, Examples of structural
proteins are myosin of muscles, keratin of skin and hair and collagen of
connective tissue.
In recent years, materials composed of or containing structural proteins have been studied and
developed as biomedical, apparel, and structural materials.
Secretary Proteins
The proteins secreted by organisms in a semi-fluid form
e.g. Fibroin is a protein secreted by spiders and silkworms to form webs and cocoons.
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Toxic Proteins
Some of the proteins are toxic in nature. Ricin present in castor bean
Enzyme inhibitors such as trypsin inhibitor
Lectin, a toxic protein present in legumes, agglutinates red blood cells
A bacterial toxin causes cholera, which is a protein. Snake venom is protein in
nature.

48. Functional Classification
Supportive Proteins
Proteins have a pivotal role in the stabilization of many structures. Examples are α-
keratins, collagen and elastin.
They generate movement.
the contraction of the muscle fibers (of which myosin is the main component);
the propulsion of spermatozoa and microorganisms with flagella;
the separation of chromosomes during mitosis.
Proteins for Regulation of Gene Expression
They control development and differentiation.
Some proteins are involved in the regulation of gene expression. An example is the
nerve growth factor (NGF), discovered by Rita Levi-Montalcini, that plays a leading
role in the formation of neural networks.
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Exotic Proteins
Antarctic fishes live in -1.9oC waters, well below the temperature at which their blood
is expected to freeze. These fishes are prevented from freezing by antifreeze
glycoproteins present in their body.

49. Over All shape of Protein molecule is determined On the Basis of
AXIAL Ratio
i.e. Length/Width ratio
Fibrous Proteins Globular Protein
49

50. Shape &Size Based Classification
Fibrous Proteins
• Primarily mechanical and structural functions,
• Insoluble in water as they contain, many
hydrophobic amino acids on both sides Internal
& external
• They ensure flexibility and/or strength
• They show Helix, Alfa and H-Bonding
• They expresses a supramolecular structure
• E.g. Fibroin, Collagen, Elastin & α-keratin
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51. Fibrous Proteins
Fibroin
Produced by spiders and insects. For
example produced by the silkworm, Bombyx mori.
Collagen
A family of 29 different proteins
Helps in formation of connective tissue
e.g. in Tendons, Matrix of bones, Cartilage & Cornea of eye
α-Keratins
They are entire dry proteins of nails, beaks, Hair, Hooves, Horns, Claws and wool etc.
Some are flexible, soft and extensible while other are Hard &Stiff
different stiffness and flexibility of these structures is a consequence of the number of
disulfide bonds
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52. Globular Proteins/ Spehroproteins
Properties
• a compact and more or less spherical structure, more complex than fibrous
proteins
• motifs, domains, tertiary and quaternary structures are found, in addition to
the secondary structures.
• Soluble in water
they act as:
• enzymes;
• hormones;
• membrane transporters and receptors;
• transporters of triglycerides, fatty acids and oxygen in the blood;
• immunoglobulins or antibodies;
• grain and legume storage proteins.
• e.g. myoglobin, hemoglobin, and cytochrome c.
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53. Classification Based on
Nutritive Value
The nutritive value of proteins is determined by the composition of essential amino acids.
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54. Proteins
Complete
Proteins
Incomplete
Proteins
Partially
Complete
Proteins
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55. Nutritive Value
Complete Proteins
The proteins having all of ten essential amino acids in the required proportion by the
Human body to promote moderate growth. E.g. Egg albumin & Milk casein.
Partially Incomplete/Partially Complete Proteins
These Proteins Partially lack one or two amino acids of ten essential amino acids,
and can promote moderate growth rate e.g. Wheat and Rice proteins (Lysine,
Thymine)
Incomplete Proteins
These proteins completely lack one or More essential amino acids of ten. So, they
can’t promote moderate growth e.g. Gelatin (Lacks Tryptophan), Zein (Lacks
Tryptophan and Lysine)
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