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Human Health and Disease — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYHuman Health and Disease1 Mark
MCQ
For question two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Immunoglobutin functions as antibody.
Reason: Different inununoglobulins molecules have different antigen binding properties.
  • A
    Both assertion and reason are true and reason is the correct explanation of assertion.
  • ✓
    Both assertion and reason are true but reason is not the correct explanation of assertion.
  • C
    Assertion is true but reason is false.
  • D
    Both assertion and reason are false.
✓

Answer

Correct option: B.
Both assertion and reason are true but reason is not the correct explanation of assertion.
Immunoglobulins are a complex hetero $-$ geneous mixture of proteins that are produced by plasma cells in response to an immunogen. It generally assume one of two roles$- (i)$ plasma membrane bound antigen receptors on the surface of $B$ cell, or $(ii)$ as antibodies free in cellular fluids functioning to intercept and eliminate antigenic determinants. It exhibit two fundamental types of structural variation. Subtle structural differences in their antigen combining sites, or variable regions, account for their unique antigen binding specificities. Structural differences outside their antigen combining sites, in the so$-$called constant regions, correlate with the different effector functions mediated by antibodies, such as complement activation or binding to one or more of the antibody $Fe$ receptors expressed on monocytes and granulocytes. The variable and constant regions of antibodies arise from distinct structural domains. Each antibody class is distinguished by certain effector functions and structural features including a unique heavy $(H)$ chain isotype, designated $\alpha (\text{IgA)},\delta (\text{IgD}),\in(\text{IgE}),\gamma(\text{IgG}),\mu(\text{IgM}).$

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