Protein Biochemistry | BSc & MSc .

Introduction

Proteins are large, complexmolecules that play many critical roles in the body.
They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs.
These proteins provide structure and support for cells. On a larger scale, they also allow the body to move.
Chemically proteins are the polyamides and are derived from alpha amino acid.
They are made from 20 odd amino acids.
The different sequence of 20 amino acids give a very large number of protein.
The protein is the principle material of skin, muscle, tendons nerves, blood enzymes, antibodies and hormones.

Structure of protein

Primary structure of the protein

The primary structure of a protein refers to the sequence of amino acids in the polypeptide chain.
The primary structure is held together by peptide bonds that are made during the process of protein biosynthesis.
The sequence of a protein is unique to that protein, and defines the structure and function of the protein.

Importance of primary structure of the protein

The high level of protein dependent on the primary structure.
Even if a single amino acid is changed from the sequence. It is called mutation and effect of the great effect on the function.
In normal amino acid, the 6^th acid in beta chain is glutamic acid and if it is changed to valine in hemoglobin, it is called sickle cell anemia.

Secondary structure of the protein(Helix or Local folding)

The most common types of secondary structures are the α helix and the β pleated sheet.
Both structures are held in shape by hydrogen bonds, which form between the carbonyl O of one amino acid and the amino H of another.
Secondary structure of protein explains about polypeptide chain folding pattern such as helix, sheet and turns.
Secondary structure preserved by non covalent forces.
Hydrogen bond
Hydrophobic bond
Electrostatic bond
Vander Waal’s forces
The secondary and tertiary structure of proteins are preserved by non – covalent forces.
They are

Hydrogen bond
Electrostatic bond
Hydrophobic bond
Vander Waal’s forces
On the basic of nature of hydrogen bonding (intermolecular and intra molecular ), Pauling and Corey identified two main types of secondary structure of proteins;