Antibodies-Immunoglobulins Long Essays
Question 1. Define and classify antibodies and add a note on the structure and function of IgG.
Answer:
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]
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IgG:
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.
- Two Identical Heavy Chains (H) Chains
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
Answer:
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.
Immunoglobulin Structures:
- Immunoglobulin consists of
- Two heavy chains
- Two light chains.
- 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)
Question 2. IgA/Secretory Immunoglobulin.
Answer:
IgA
IgA is the second major serum immunoglobulin
- IgA 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.
- S (Secretory) Piece is glycine -rich polypeptide.
- S (Secretory) Piece is produced by mucosal or glandular epithelial cells.
- S (Secretory) Piece protects IgA from denaturation by bacterial proteases.
- Two Alpha-Heavy Chains
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.
Answer:
Functions Of Antibodies
Question 2. Structure of IgM
Answer:
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.