Question

How many classes of immunoglobulin are there in humans?
A. 3
B. 4
C. 5
D. 6

Answer 1

Hint: Immunoglobulin are antibody molecules which are composed of glycoprotein molecules of one or more units. Each of the immunoglobulin molecules contains four polypeptide chains of which two are identical heavy chains and other two are identical light chains.

Complete answer:
The amino terminal ends of the polypeptide chain show some variation in amino acid composition and are referred to as the variable (V) region to distinguish them from relatively constant (C) regions. There are five classes of immunoglobulin which are IgG, IgA, IgM, IgE and IgD. These all five classes are different by type of heavy chain which is found in the molecule. IgA have alpha-chains in these molecules. IgG molecules have very heavy chains known as gamma-chains in them. IgM have mu-chains in them, IgD have delta-chains in them and IgE have epsilon-chains in them.
Differences in heavy polypeptides chain which allow immunoglobulins which function in different types of immune responses and at particular stages of the immune response. Antibody IgM antibodies have five Y-shaped units which are called pentamers which contain a total of 10 heavy chains, 10 light chains and 10 antigen-binding. There are two main types of light chains which are kappa and lambda.

Hence, the correct option is C. 5.

Note: The immunoglobulin have light and heavy chains are held together by a combination of non-covalent interaction and covalent interchain which form a bilaterally symmetric structure. The V regions of L and H chains comprise the antigen-binding site of immunoglobulin molecules.