Question

The structural level of a protein least affected by a disruption in hydrogen bonding is the

(A) primary level

(B) secondary level

(C) tertiary level

(D) quaternary level

Short answer

(A) The option “primary level” is true.

(B) The option “secondary level” is false.

(C) The option “tertiary level” is false.

(D) The option “quaternary level” is false.

Step-by-step solution

Hydrogen bonding 

Proteins are abundant biomolecules that are made from amino acids. These amino acids are classified into acidic, basic, and neutral categories, which define protein property.

Based on structure and shape, proteins are studied at four levels: primary, secondary, tertiary, and quaternary, with each level getting a bit more complex than the last one.

Explanation for option ‘(A)’ 

The sequence of amino acids defines the primary structure of the protein. If the protein’s primary structure shows any change, then the new sequence will define a different protein.

If the hydrogen bonding is disturbed in the protein or there is breakage of the hydrogen bond, then the primary structure of the protein is least distorted because there is no hydrogen bonding at this level.

Thus, the option is true.

Explanation for option ‘(B)’

The secondary structure of the protein defines the shape of a protein in which the polypeptide chain can arrange itself. These are found in two basic forms, which are alpha helix and beta pleated.

Alpha-helix and beta-pleated sheet structures are formed due to specific folding of the backbone of the polypeptide chain. The hydrogen bond is present at this level, so they are affected by the hydrogen bond disruption.

Thus, the option is false.

Explanation for option ‘(C)’

The tertiary structure of the protein defines the overall shape or folding of the protein. This structure is stabilized by different kinds of bonding, such as disulfide linkage, Van der Waals force, and hydrogen bonds.

In some cases, electrostatic forces of attraction are also observed. So, they show much impact on the disruption of hydrogen bonding.

Thus, the option is false.

Explanation for option ‘(D)’ 

Few out of thousand proteins are made up from different subunits, or one can say two or more polypeptide chains. This kind of spatial arrangement of different subunits concerning each other defines the quaternary structure of a protein.

This kind of structure is held together by the non-covalent bonds and disulfide linkages. So, it is not much affected by the disruption of hydrogen bonding.

Thus, the option is false.