Question

"what part of the antibody's structure determines its class?"

Answer 1

The propositions are:
A light (L) chainB constant (C) regionC variable (V) regionD heavy (H) chain

The right answer is B constant (C) region

The immunoglobulin molecule has two distinct functions:
the first is to bind specifically to molecules of the pathogen that has induced the immune response;
the second is to recruit cells or molecules capable of destroying the pathogen against which it is directed.
These functions are structurally separated on the immunoglobulin molecule.

*The part responsible for binding to the antigen, whose structure is extremely variable from one immunoglobulin molecule to another, is called the variable region. This variability allows each immunoglobulin to recognize a particular antigen. The entire antibody repertoire of an individual is diverse enough to allow recognition of any antigen.

*The region of the molecule responsible for the effector functions does not vary so much. This region is called a constant region although in fact it can exist in five different forms. These five forms characterize the isotype of the immunoglobulin molecule. It is the isotypes that are specialized in the activation of this or that effector mechanism.

Answer 2

Out of the following given choices;
A) light (L) chain B) constant (C) regionC) variable (V) regionD) heavy (H) chain
The answer is B. This region is called the Fc region and composed of only heavy polypeptide chains only. It is used to classify antibody according to class. There are IgM, IgA, IgG, IgE, and IgD. Fab is the varying region of the antibody that is significant in binding antigens.