Name of student : Madhusha .M.L Name of college : New B.Ed college,Nellimoodu

Option : Natural Science Candidate code :

181/13376014

PROTEINS

PROTEINS

• Proteins are high molecular weight compounds made of amino acids linked to one another by peptide bonds.

• On hydrolysis proteins yield amino acids

• Thus amino acids are considered as the building blocks of proteins.

All proteins invariably contain carbon, hydrogen, oxygen and nitrogen.

some proteins contain sulphur and phosphorus as minor constituents.

Proteins have great importance in living systems.

They are indispensable for biological structure and function.

CLASSIFICATION OF PROTEINS

There exist several arbitrary systems of classification for proteins.

Based on the increasing complexity of structure, proteins are mainly classified in to three groups.

They are the simple proteins, the conjugated proteins and the derived proteins.

SIMPLE PROTEINS

Those proteins which yield only amino acids and their derivatives on hydrolysis are called simple proteins.

They are further subdivided into seven subclasses in the order of decreasing solubility.

They are albumins, globellins, glutellins, prolamines, scleroproteins, histones and protamines.

CONJUGATED PROTEINS

• These are the proteins which contain a non protein component (prosthetic group) in addition to the protein part.

• The important types of conjugated proteins

are nucleoproteins, glycoproteins, lipoproteins, chromoproteins, phosphoproteins and metalloproteins.

DERIVED PROTEINS

These are the products obtained when native proteins are degraded by acids, alkalis or enzymes.

Some of the derived proteins which are the degradation products include proteoses, peptones, peptides etc.

STRUCTURAL LEVELS OF PROTEINSA protein may consist of one or more

polypeptide chains.The linear chains of polypeptides are

arranged in space in various ways to give higher structural configurations to proteins.

The different levels of structural organization shown by proteins are primary, secondary, tertiary and quaternary.

Primary structure refers to the number, nature and sequence of amino acids in the polypeptide chain.

Secondary structure describes the conformation of the polypeptide chains present in the protein molecule.

There are two basic types of secondary structure namely alpha helix and beta pleated sheet.

The tertiary structure of a protein refers to

its three dimensional structure which describes the spatial arrangement of polypeptide chains.

In quaternary structure the polypeptide chains will aggregate in a certain way to form a functional unit.

VARIOUS STRUCTURAL LEVELS OF PROTEINS

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