Introduction of Proteins Classification of Proteins Types and Structure of Proteins

1. PROTEINS
By
SHILANJALI. B
Research scholar
Gulbarga University
Kalaburagi

2. INTRODUCTION
• Proteins were first described by the Dutch chemist Gerardus
Johannes Mulder and named by the Swedish chemist Jöns Jacob
Berzelius in 1838.
• The term protein is derived from a greek word “proteios” meaning
“holding the first place”
Gerardus Johannes
Mulder
Jöns Jacob Berzelius

3. • Protein consisting of one or more long chains of amino acid
residues.
• Proteins are large biomolecules, or macromolecules.
• Proteins perform a vast array of functions within organisms,
including catalysing metabolic reactions, DNA replication,
responding to stimuli, providing structure to cells, and
organisms, and transporting molecules from one location to
another.

4. CLASSIFICATION OF PROTEIN
A. FUNCTIONAL CLASSIFICATION OF PROTEINS
1. Structural proteins:- keratin of hair, nail, collagen of bone.
2. Enzymes or catalytic proteins:- Hexokinase, pepsin
3. Transport proteins:- Haemoglobin, serum albumin
4. Hormonal proteins:- Insulin, growth hormone
5. Contractile proteins:- Actin, myosin
6. Storage proteins:- Ovalbumin, glutelin.
7. Genetic proteins:- Nucleoprotein.
8. Defence proteins:- Snake venoms, immunoglobulin's
9. Receptor proteins :- for hormones, viruses

5. B. PROTEIN CLASSIFICATION BASED ON CHEMICAL NATURE
AND SOLUBILITY
1. Simple proteins:- They are composed of only amino acid
residues.
2. Conjugated proteins:- Beside the amino acids, these proteins
contain a non-protein moiety known as prosthetic group or
conjugating group
3. Derived proteins:- These are the denatured or degraded
products of simple and conjugated proteins.

6. C. Nutritional classification of proteins
1. Complete proteins:- These proteins have all nine essential
amino acids in the required proportion by the human body to
promote good growth. E.g:- egg albumin, milk casein
2. Partially proteins:- These proteins partially lack one or more
essential amino acids, and can promote moderate growth.
Eg.:- wheat and rice proteins.
3. Incomplete proteins:- These proteins completely lack one or
more essential amino acids. Hence they do not promote
growth at all. Eg:- gelatin.

7. Essential and non Essential amino acids

8. Classification of proteins

9. BOND RESPONSIBLE FOR PROTEIN STRUCTURE
Protein structure is stabilized by two types of bonds: –
Covalent and Non-covalent
1. Covalent bonds:- the peptide and disulfied bonds are strong in
protein structure.
2. Non-covalent:- there are mainly four type of Non-covalent
bonds.
a. Hydrogen bonds
b. Hydrophobic bonds
c. Electrostatic bonds
d. Van der Waals forces

10. • Proteins which are mixed polymers of amino acids can have
up to four structural level
• Primary proteins.
• Secondary proteins.
• Tertiary proteins.
• Quaternary proteins.
PROTEIN STRUCTURE

11. • The primary structure of a polypeptide is its amino acid
sequence. The amino acids are connected by peptide bonds
written left-to-right from the N-terminus to the C-terminus.
• Primary structure of polypeptide determines the higher levels of
structural organization
PRIMARY STRUCTURE

12. SECONDARY STRUCTURE
• The conformation of polypeptide chain by
twisting or folding is referred to as secondary
structure.
• Two types of secondary structure, α – Helix
and β – sheet
α – Helix :- proposed by Pauling and Corey
(1951), it is most common spiral structure of
protein.
E.g. ( Fibrous protein)
β – sheet :- proposed by Pauling and Corey
(1951), are composed of two or more segments
of fully extended peptide chains.
E.g. ( globular protein) α – Helix β – sheet

13. SUPERSECONDARY OF
PROTEIN STRUCTURE
• The intermediate protein
structure between secondary
and tertiary structure are often
referred to as supersecondary
structure
• The term motif is sometimes
used described the
supersecondary protein
structure

14. • The three- dimensional arrangement of protein structure is
referred to as tertiary structure.
• It is compact structure with hydrophobic(interior) hydrophilic
(surface) of protein molecule
• Bonds :- disulfied bonds (-S-S-), ionic interaction, hydrophobic
and van der Waals forces.
• Term as domain used to represent the basic units of proteins
structure and function
TERTIARY STRUCTURE
TERTIARY
STRUCTURE

15. • It consists of two or more polypeptide which may be identical
or unrelated, such protein are termed as oligomers and possess
quaternary structure.
QUATERNARY STRUCTURE

17. 1. Solubility:- Proteins from colloidal solutions instead of true
solutions in water. This is due to huge size of protein molecules.
2. Molecular weight:- The protein vary in their molecular weights,
average molecular weight of amino acid about 110 mol.
3. Shape:- The shape of protein it may be globular and fibrous.
4. Isoelectric pH:- amino acids as ionisable group which determine the
PI of a protein, it exits zwitterions or dipolar ions.
5. Acidic and basic:- proteins greater than 1 are referred to as a basic
proteins. For acidic proteins, the ratio is less than 1.
6. Precipitation of protein:- proteins can be precipitated by
dehydration or neutralization of polar group.
7. Colour reaction of protein:- The proteins give several colour
reactions which are often useful to identify the nature of the amino
acids present in them.
PROPERTY