Question

Tertiary Structure

20. How many polypeptide chains are present in the tertiary structure of a protein?

21. Tertiary structure is the irregular loops and folds of a polypeptide chain. Draw a representation of tertiary structure.

22. The irregular loops and folds of tertiary structure form because of interactions between which portions of the polypeptide chain? (Select one)

1. Backbone atoms

2. Side chains/R groups

In the Table below,  

23. List the different types of interactions that can occur at the level of tertiary protein structure.

24. Provide a description for each of these interactions.

	23. Interaction name	24. Description
a.
b.
c.
d.

Answer 1

20. How many polypeptide chains are present in the tertiary structure of a protein?

In general, 1 poplypeptide chain is present in tertiary structure of a protein. However it may also contain more than one polypeptides in some cases.

21. Tertiary structure is the irregular loops and folds of a polypeptide chain. Draw a representation of tertiary structure.

22. The irregular loops and folds of tertiary structure form because of interactions between which portions of the polypeptide chain? (Select one)

Answer -  Side chains/R groups

The R groups interact with each other through several bonds and interactions resulting in protein folding.

In the Table below,  

23. List the different types of interactions that can occur at the level of tertiary protein structure.

24. Provide a description for each of these interactions.

a. Hydrophobic interactions - These are non-covalent interactions between hydrophobic amino acid R- chains which cluster around each other to reduce the net surface area exposed to water.

b. Hydrogen bonds - It is a dipole-dipole interaction . In this, a hydrogen atom which is covalently bonded to an electronegative atom and another very electronegative atom are attracted towards each other.

c. van der Waals force of interaction - These are very weak induced forces of interaction between atoms of neutral molecules. It is an attractive force between polar and non-polar molecules over large distances.

d. Covalent bonds - In case of proteins, the covalent bonds formed are disulphide bonds or disulphide bridges. The enzyme Protein Disulfide Isomerase catalyses the formation of disulphide bridges between two cysteine residues.