This document provides an introduction and overview of protein classification and properties. It discusses how proteins are classified based on their source, shape, composition and solubility, as well as their biological functions. Key points include that proteins are composed of amino acids and can have globular or fibrous shapes. Conjugated proteins are linked to non-protein groups. Insulin is an important protein hormone that regulates blood sugar levels and was the first to be fully sequenced. The document also examines general protein properties like molecular weight and reactions involving amino acid groups.
2. INTRODUCTION
• Protein name is derived from a
Greek word PROTOS which
mean “ the first or supreme”.
• Protein are extremely
complicated .
• 20 amino acids which have been
found to occur in all proteins,
known as standard amino acid.
• 21st amino acid; Selenocysteine
• 22nd amino acid; Pyrrolysine
4. CLASSIFICATION BASED ON THE
SOURCE OF PROTEIN MOLECULE
• Animal proteins are the proteins derived from animal sources such as eggs,
milk, meat and fish. They are usually called higher-quality proteins.
• On the other hand, plant proteins are called lower-quality proteins.
• The four most common limiting amino acids are methionine, lysine,
threonine and tryptophan.
5. CLASSIFICATION BASED ON THE SHAPE OF
PROTEIN MOLECULE
Globular protein or Corpuscular Proteins :-
• These have an axial ratio (length : width) of less than 10 (usually not over 3 or 4) and,
henceforth, possess a relatively spherical or ovoid shape.
• These are usually soluble in water.
How can we remember the examples:- GHARMII
• G Globin (protein part of Haemoglobin)
• H Histone (Eukaryotic DNA)
• A Albumin (Maintain BCOP*)
• R Rubisco ( Enzyme in Calvin cycle)
• M Myoglobin ( Pigment in muscle for O2 transport)
• I Insulin (Pancreatic hormone)
• I Immunoglobulin's (Antibodies)
• (BCOP*= Blood colloidal osmotic pressure)
6. Fibrous Proteins or Fibrillar Proteins:-
• These have axial ratios greater than 10 and, henceforth, resemble long ribbons
or fiber in shape.
• These are mainly of animal origin and are insoluble in all common solvents
such as water, dilute acids, alkalies and salts and also in organic solvents.
• The fibrous proteins are extremely strong and possess two important properties
which are characteristic of the elastomers. These are
A. They can stretch and later recoil to their original length.
B. They have a tendency to creep
Fibrous proteins
• Collagens.
• Elastins
• Keratins
• Fibroin.
7. CLASSIFICATION BASED ON COMPOSITIONAND
SOLUBILITY
Simple Proteins
These are of globular
type. This group
includes proteins
containing only amino
acids.
• Protamines (Arginine
rich)and
histones(Arginine and
lysine)
• Albumins; water soluble
• Globulins; insoluble in
water
• Globins; rich in histidine
• Prolamines; present in
sperm cells
• Scleroproteins or
Albuminoids
Conjugated Proteins
These are the proteins
linked with a separable
nonprotein portion
called prosthetic group.
• Metalloproteins
• Chromoproteins.
• Glycoproteins and
Mucoprotein
• Phosphoproteins
• Lipoproteins
• Nucleoproteins
Derived Proteins
Protein derived from
simple and conjugated
protein by chemical and
physical treatment.
I. Primary derived
proteins.(insoluble in
water)
• Metaproteins or
Infraproteins
• Coagulated Proteins
II. Secondary derived
proteins.(soluble in water)
• Proteoses
• Polypeptides
8.
9. Conjugated proteins Protein part Prosthetic group
Haemoglobin
(transfer of oxygen in
body from lungs to the
tissue)
Globin Heme
(bone marrow and liver)
Nucleoprotein
( transcription, translation,
regulating gene
expression)
Histones DNA
Rhodopsin
( the primary
photoreceptor molecule
of vission)
Opsin 11-cis-retinal
(Vit. A aldehyde)
Ferritin
(store iron inside the cell)
Aproferritin Iron
Lipoprotein
(they carry cholesterol
through the blood stream
to the cell)
Protein Lipid (Fats)
13. EGG PROTEINS:-
The eggs and milk are consumed as food by an appreciable portion of the
global population. Hence, the egg and milk proteins deserve a special mention.
Eggs contain 2 types of proteins : the egg white protein and egg yolk protein.
Egg yolk contains 2 phosphoproteins, lipovitellin and lipovitellenin.
Egg yolk also contains water-soluble protein that does not precipitate on dilution
of the yolk. This fraction is called livetin.
Whole egg is an excellent food because it is a very rich source not only of
protein and lipid but also of most of the vitamins (except vitamin C) and most of
the required minerals (except calcium).
14. General Properties
1) Colour and Taste.
2) Shape and Size.
3) Molecular Weight.
4) Colloidal Nature.
5) Amphoteric Nature.
6) Solubility.
PHYSICAL CHEMICAL
A. Hydrolysis.
B. Reactions Involving
COOH Group.
C. Reactions Involving NH2
Group.
D. Reactions Involving Both
COOH And NH2 Groups.
E. Reactions Involving R
Group Or Side Chain.
15.
16.
17. Chemical properties
A. HYDROLYSIS:- (using acidic group)
B. REACTIONS INVOLVING COOH GROUP
• Reaction with alkalies (Salt formation)
• Reaction with alcohols (Esterification)
18. • Reaction with amine:-
C. REACTIONS INVOLVING NH2 GROUP:-
• Reaction with mineral acids (Salt formation)
D. REACTIONS INVOLVING BOTH COOH AND NH2 GROUPS:-
• Reaction with phosgene
19. PHYSICALAGENTS:-
Heat, UV, high pressure.
CHEMICALAGENTS:-
Acids, alkalis, heavy metals, detergents(SDS), urea etc.
EXAMPLE OF DENATURATION:- PANEER
EXAMPLE OF RENATURATION:- SDS denaturation can be reversed
20. E. REACTIONS INVOLVING R GROUP OR SIDE CHAIN:-
• Colour reactions for specific amino acids
21. INSULIN:-
• Insulin ( from Latin insula, 'island').
• It is considered to be the main anabolic hormone of the body.
• Porcine insulin is especially close to the human version, and was
widely used to treat type 1 diabetics before human insulin could be
produced in large quantities by recombinant DNA technologies.
• Frederick Sanger sequenced the amino acid structure in 1951,
which made insulin the first protein to be fully sequenced.
• Insulin is also the first protein to be chemically synthesized and
produced by DNA recombinant technology.
• Researchers have succeeded in introducing the gene for human
insulin into plants as another method of producing insulin
("biopharming") in safflower. This technique is anticipated to reduce
production costs.
