Proteins can be classified on many different bases as:
on the basis of chemical nature and solubility: It is based on the amino acid composition and is divided into three major classes as
SIMPLE PROTEIN: these are made up of amino acids residue only
1 Globular protein: these are spherical and oval in shape, soluble in water and other solvents and digestable
a) albumin e.g. egg
b) globulin: soluble in neutral dilute salt solution e.g. serum globulin
c) proalamines: soluble in 70% alcohol e.g. gliadin and zein maize
d) histones: basic protein soluble in water and dilute acids
On the basis of functions of protien:
1 Structural protein: e.g. keratin
2 Enzyme and catalytic protein: e.g. pepsin
3 Transport protein: Hb, serum albuin
4 Hormonal protein: e.g. hormones as insulin, adrenalin
5 Contractile protein: e.g. actin and myosin
6 Storage protein: e.g. oval albumin, glutamin
7 Genetic protein: e.g. nucleic acid ( DNA & RNA)
8 Defence protein: e.g. Ig, snake venom
9 Receptor protein: hormones and viruses