CLASSIFICATION OF AMINO ACID:
There are two types of amino acids as per the nutritional requirement.They are classified into essential and non-essential amino acids.
Essential amino acids are those that are not synthesized by the body and are needed in the diet. Methionine, threonine, tryptophan, valine, isoleucine, leucine and phenylalanine are the essential amino acids.
Non-essential amino acids are those that are synthesized in the body and are not necessary in the diet. Glycine, alanine, serine, cysteine, tyrosine, proline, aspartic acid and glutamic acid are the non-essential amino acids.
CLASSIFICATIONS OF PROTEINS :
Proteins are classified based on their composition. They are of two types:
Simple proteins are those which contain only amino acids.Example: Egg albumin and seed globulin.
Conjugate proteins are those which contain a non-amino acid component in addition to the amino acids. This non-amino acid component is called the prosthetic group. For e.g., glycoprotein (with carbohydrate as the prosthetic group), phosphoprotein (with phosphate as the prosthetic group), lipoprotein (with lipid as the prosthetic group).
Classification of Proteins According to Shape and Solubility:
Proteins can be broadly classified into three groups, based on their shape and solubility.
These are protein which are in association with lipid membranes. Those membrane proteins that are embedded in the lipid bilayer have extensive hydrophobic amino acids that interact with the non-polar environment of the bilayer interior. Membrane proteins are not soluble in aqueous solution. Rhodopsin is an example of a membrane 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
Fibrous proteins: These proteins have a rod like structure. They are not soluble in water. Collagen is an example of a fibrous protein.