Antibodies Immunoglobulins Short And Long Essays Question And Answers

Antibodies-Immunoglobulins Long Essays

Question 1. Define and classify antibodies and add a note on the structure and function of IgG.

Antibodies  Definition:

  • Antibodies are substances which are formed in the serum and tissue fluids in response to an antigen and react with that antigen specifically and in some observable manner.

Antibodies  Classification:

  • Antibodies are named as immunoglobulins.
  • There are five groups of immunoglobulins (Ig]

Antibodies Immunoglobulins Five groups of immunoglobulins


IgG Structure:

  • IgG consists of
    • Two identical heavy chains (H) chains
      • They are gamma chains.
      • Held together by disulphide bonds (S-S)
      • They are longer chains.
      • Consists of a smaller variable (V) region and a longer constant (C] region.
    • Two identical light (L) chains.
      • Present in two forms. Kappa (K) and Lambada (L)
      • Attached to heavy chains by disulphide bonds.
      • They are shorter chains.
      • The init variable and constant region are equal.
      • Variable regions are present at the amino terminus
      • The amino acid sequence here is highly variable.
      • Constant region is present at the carboxy terminus.

Antibodies Immunoglobulins IgG molecule

IgG Functions:

  • Can be transported through the placenta
  • Thus, provide natural passive immunity to the newborn.
  • Participates in precipitation, complement fixation and neutralisation of toxins and viruses.
  • Protects against active micro-organisms present in the blood and tissues.

Antibodies Immunoglobulins Short Essays

Question 1. Immunoglobulin



  • Immunoglobulin is defined as a protein of animal origin endowed with known antibody activity.

Immunoglobulin Synthesis:

  • They are synthesized by plasma cells and by lymphocytes.

Read And Learn More: Microbiology Question and Answers

Immunoglobulin Structures:

  • Immunoglobulin consists of
    • Two heavy chains
    • Two light chains.

Antibodies Immunoglobulins Immunoglobulin Sttructures

  • The variable region is present at the amino terminus while the constant region is present at the carboxy terminus.
  • Based on the heavy chains. Immunoglobulins are classified into 5 classes.
  • Light chains in all the classes are Kappa (K) and lambda (L)

Antibodies Immunoglobulins Light chains Classes

Antibodies Immunoglobulins Structure of immunoglobulin

Question 2. IgA/Secretory Immunoglobulin.


IgA is the second major serum immunoglobulin

  • It is the fast-moving alpha-globulin.

Serum Concentration:

  • Normal serum concentration – 0.6 – 4.2 mg/ml.
  • It is about 10 – 13% of total serum immunoglobulin.
  • Half-life: 6 – 8 days

IgA  Forms:

  • IgA is present in two forms.
    • Serum IgA
    • Secretory IgA

IgA  Structure:

  • IgA is a dinner consisting of two monomer units.
  • It consists of
    • Two alpha-heavy chains
      • Joined by disulphide bonds.
    • Two kappa (K) or lambda (L) light chains.
      • Attached to heavy chains by disulphide bonds
    • I Chains
      • It is glycoprotein
      • It joins the two monomer units of IgA
    • S (secretory) piece.
      • It is glycine -rich polypeptide.
      • It is produced by mucosal or glandular epithelial cells.
      • It protects IgA from denaturation by bacterial proteases.

Antibodies Immunoglobulins Secretory IgA molecule

IgA  Synthesis:

  • Locally from plasma cells.
  • In trace amount from serum.

IgA  Functions:

  • IgA, is present in secretions such as milk, saliva, tears, sweat, nasal fluids, colostrums and in secretions of respiratory, intestinal and genital systems.
  • Hence called secretory immunoglobulin.
  • Protects mucous membranes against micro-organisms.

Antibodies Immunoglobulins Short Question And Answers

Question 1. Functions of antibodies.

Functions of antibodies

Antibodies Immunoglobulins Functions Of Antibodies

Question 2. Structure of IgM

IgM Structure:

  • IgM is a pentamer consisting of 5 immunoglobulin subunits and one molecule of J chain.
  • J chain joins the Fc region of basic subunits.
  • Each subunits consists of
    • Two identical mu heavy (H) chains and
    • Two identical Kappa (K) or Lambda (L) light chains.
  • These chains are held together by disulphide bonds.
  • Both chains have a variable (V) region and a constant (C) region.

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