Question

explain primary, secondary, tertiary and Quaternary structure of protein ​

Answer 1

Answer:

1. Primary Structure of Protein

The Primary structure of proteins is the exact ordering of amino acids forming their chains.

The exact sequence of the proteins is very important as it determines the final fold and therefore the function of the protein.

The number of polypeptide chains together form proteins. These chains have amino acids arranged in a particular sequence which is characteristic of the specific protein. Any change in the sequence changes the entire protein.

2. Secondary Structure of Protein

The proteins do not exist in just simple chains of polypeptides.

These polypeptide chains usually fold due to the interaction between the amine and carboxyl group of the peptide link.

The structure refers to the shape in which a long polypeptide chain can exist.

They are found to exist in two different types of structures α – helix and β – pleated sheet structures.

This structure arises due to the regular folding of the backbone of the polypeptide chain due to hydrogen bonding between -CO group and -NH groups of the peptide bond.

However, segments of the protein chain may acquire their own local fold, which is much simpler and usually takes the shape of a spiral an extended shape or a loop. These local folds are termed secondary elements and form the proteins secondary structure.

3. Tertiary Structure of Protein

This structure arises from further folding of the secondary structure of the protein.

H-bonds, electrostatic forces, disulphide linkages, and Vander Waals forces stabilize this structure.

The tertiary structure of proteins represents overall folding of the polypeptide chains, further folding of the secondary structure.

It gives rise to two major molecular shapes called fibrous and globular.

The main forces which stabilize the secondary and tertiary structures of proteins are hydrogen bonds, disulphide linkages, van der Waals and electrostatic forces of attraction.

4. Quaternary Structure of Protein

The spatial arrangement of various tertiary structures gives rise to the quaternary structure. Some of the proteins are composed of two or more polypeptide chains referred to as sub-units. The spatial arrangement of these subunits with respect to each other is known as quaternary structure.

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Answer 2

Answer:

Tertiary structure:

• The long protein chain of the

polypeptide chain usually folds

upon itself like a hollow woollen

ball. This is termed as tertiary

structure. This structure gives a

3-dimensional view of protein.

• Tertiary structure is absolutely

necessary for the many

biological activities of proteins

for example, this structure

brings distant amino acid side

chains closer forming the active

site (the site to which a

substrate gets attached) of

proteins i.e., enzymes. e.g.,

Myoglobin (protein found in

muscle cell)