Question

Denaturation of protein leads to loss of its biological activity by:
A: formation of amino acids
B: loss of primary structure
C: loss of both primary and secondary structure
D: loss of both secondary and tertiary structures

Answer 1

Hint: Denaturation is linked with the breaking of most of the weak bonds or linkages (like hydrogen bonds), in a protein molecule that are mainly responsible for the highly ordered protein structure in its natural or native state. Denatured proteins generally have a looser or more random structure and most of them are insoluble. In other words, denatured proteins do not have biological activity and no longer perform specific biological functions.

 Complete step by step answer:
Heat denaturation of proteins includes the configurational changes in native structures of the protein (that are thermodynamically stable) through unfolding or alteration of the secondary, ternary or quaternary structure as a response to heat subjection. Denaturation may destroy hydrogen and disulfide bonds, salt bridges and hydrophobic interactions but peptide bonds remain unbroken. Moreover, the primary structure, or we can say, amino acid sequence of the protein remains unaltered and also the molecular weight. A loss of ordered structure usually takes place in the entropy-driven transformation from a native to a denatured protein. The temperature at which denaturation takes place vary greatly with the source of protein and type. Few proteins unfold a few degrees higher than the temperatures at which they normally function, whereas others, for example, wheat gluten or milk β-casein, need much higher temperatures for their denaturation. On the other hand, globular dairy whey proteins lead to denaturation at much lower temperatures in comparison to casein proteins which have more random coil native structures.
Therefore, denaturation of protein leads to loss of its biological activity by (D) loss of both secondary and tertiary structures


Note:
The main causes of protein denaturation are heat, intense agitation, ultraviolet light, and strong bases and acids. Unlike nucleic acids, protein renaturation does not occur readily, even when they are placed in a biologically friendly environment.