4. Name the four different types of interactions responsible for creating tertiary structures in proteins and elaborate the same.

 4. Name the four different types of interactions responsible for               creating tertiary structures in proteins and elaborate the                       same.

answer : 

TERTIARY STRUCTURE :

A protein’s distinctive three-dimensional shape, or tertiary structure, results from interactions between residues that are brought together as the chain bends and folds in space. The residues that interact with one another are often far apart in the linear sequence. In contrast to secondary structures, which involve only hydrogen bonds between backbone components, tertiary structures form using a variety of bonds and interactions between R-groups or between R-groups and the backbone. 

Five types of interactions involving R-groups are particularly important: 

1. Hydrogen bonding : Hydrogen bonds form between polar side chains and opposite partial charges either in the peptide backbone or other R-groups.

 2. Hydrophobic interactions: In an aqueous solution, water molecules interact with the hydrophilic polar side chains of a polypeptide, forcing the hydrophobic nonpolar side chains to coalesce into globular masses. When these non polar R-groups come together, the surrounding water molecules form more hydrogen bonds with each other and the polar residues on the surface of the protein, increasing the stability of their own interactions and the disorder of the aqueous solution. 

3. van der Waals interactions: Once hydrophobic side chains are close to one another, their association is further stabilized by electrical attractions known as van der Waals interactions. These weak attractions occur because the constant motion of electrons gives molecules a tiny asymmetry in charge that changes with time. If nonpolar molecules get extremely close to each other, the minute partial charge on one molecule induces an opposite partial charge in the nearby molecule and causes an attraction. Although the interaction is very weak relative to covalent bonds or even hydrogen bonds, a large number of van der Waals interactions can significantly increase the stability of the structure.

4. Covalent bonding: Covalent bonds can form between the side chains of two cysteines through a reaction between the sulfhydryl groups. These disulfide (“two-sulfur”) bonds are  frequently referred to as bridges, because they create strong links between distinct regions of the same polypeptide or two separate polypeptides. 

5. Ionic bonding:Ionic bonds may form between groups that have full and opposing charges, such as the ionized acidic and basic side chains highlighted on the right







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