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Questions and Answers
Binding can activate the cells to perform some biological ______.
Binding can activate the cells to perform some biological ______.
functions
IgG constitutes about ______% of total Igs of the body.
IgG constitutes about ______% of total Igs of the body.
70-80
IgG has the longest ______-life of 23 days.
IgG has the longest ______-life of 23 days.
half
IgG has four subclasses- IgG1, IgG2, IgG3 and ______.
IgG has four subclasses- IgG1, IgG2, IgG3 and ______.
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IgM has the highest ______ weight, and maximum sedimentation coefficient (19S).
IgM has the highest ______ weight, and maximum sedimentation coefficient (19S).
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IgM exists in both ______ and pentameric forms.
IgM exists in both ______ and pentameric forms.
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IgA constitutes about ______% of total serum Ig.
IgA constitutes about ______% of total serum Ig.
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Dimeric IgA is composed of two ______ units joined by a J chain.
Dimeric IgA is composed of two ______ units joined by a J chain.
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An antibody is a specialized ______ produced from activated B cells
An antibody is a specialized ______ produced from activated B cells
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Antibody and ______ are used interchangeably to represent the physiological and functional properties of the same molecule
Antibody and ______ are used interchangeably to represent the physiological and functional properties of the same molecule
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There are five classes of ______ recognized: IgG, IgA, IgM, IgD, and IgE
There are five classes of ______ recognized: IgG, IgA, IgM, IgD, and IgE
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An antibody molecule is a ______ shaped heterodimer composed of four polypeptide chains
An antibody molecule is a ______ shaped heterodimer composed of four polypeptide chains
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The ______ region represents the antigen binding site of the antibody
The ______ region represents the antigen binding site of the antibody
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Antibody coating the target cell binds to ______ through its Fc receptor
Antibody coating the target cell binds to ______ through its Fc receptor
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Phagocytic cells, lymphocytes, platelets, mast cells, NK cells, eosinophils, and basophils bear ______ receptors that bind to the Fc region of immunoglobulins
Phagocytic cells, lymphocytes, platelets, mast cells, NK cells, eosinophils, and basophils bear ______ receptors that bind to the Fc region of immunoglobulins
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Each H and L chain has two ends: an ______ terminal end and a carboxyl terminal end
Each H and L chain has two ends: an ______ terminal end and a carboxyl terminal end
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Secretory IgA provides good protection to the immunologically immature infant ______.
Secretory IgA provides good protection to the immunologically immature infant ______.
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IgA exists in two ______ isotypes: IgA1 and IgA2.
IgA exists in two ______ isotypes: IgA1 and IgA2.
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IgE is the only ______ labile antibody, inactivated at 56º C in one hour.
IgE is the only ______ labile antibody, inactivated at 56º C in one hour.
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IgD is found as membrane Ig on the surface of ______ cells and acts as a B cell receptor.
IgD is found as membrane Ig on the surface of ______ cells and acts as a B cell receptor.
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The five classes of Igs and their subclasses are called as ______.
The five classes of Igs and their subclasses are called as ______.
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Isotypic variation refers to the variation in the amino acid sequences of the constant region of their ______ chains.
Isotypic variation refers to the variation in the amino acid sequences of the constant region of their ______ chains.
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Study Notes
Antibody Structure
- An antibody molecule is a 'Y-shaped' heterodimer composed of four polypeptide chains: two identical light (L) chains and two identical heavy (H) chains.
- The molecular weight of L chains is 25,000 Da each, and H chains have a molecular weight of 50,000 Da or more.
- The chains are bound together by disulfide bonds and noncovalent interactions.
Antibody Regions
- Each H and L chain consists of two regions: variable and constant regions.
- The variable region represents the antigen binding site of the antibody.
Functions of Immunoglobulins
- Effector functions are mediated by the Fc region, including fixation of complement, binding to various cell types, and activation of cells to perform biological functions.
- Immunoglobulins can cross the placenta and provide immunity to the fetus and newborn.
Immunoglobulin G (IgG)
- Constitutes about 70-80% of total Igs in the body.
- Has the longest half-life of 23 days and the highest serum concentration.
- IgG has four subclasses: IgG1, IgG2, IgG3, and IgG4, which differ in their biological functions, hinge region length, and number of disulphide bridges.
- Functions: crosses placenta, provides immunity to fetus and newborn, fixes complement, mediates phagocytosis, and neutralizes toxins.
Immunoglobulin M (IgM)
- Has the highest molecular weight and sedimentation coefficient (19S).
- Exists in both monomeric and pentameric forms.
- Functions: provides immediate immunity, fixes complement, acts as an opsonin, mediates agglutination, and is an antigen receptor.
Immunoglobulin A (IgA)
- Exists in both monomeric and dimeric forms.
- Secretory IgA provides local or mucosal immunity, effective against bacteria and viruses, and is found in body secretions like milk, saliva, tears, and intestinal and respiratory tract mucosal secretions.
Immunoglobulin E (IgE)
- Has the lowest serum concentration, shortest half-life, and minimum daily production.
- Is heat-labile and has affinity for the surface of tissue cells, especially mast cells.
- Mediates type I hypersensitivity reactions and is elevated in helminthic infections.
Immunoglobulin D (IgD)
- Is found as membrane Ig on the surface of B cells, acting as a B cell receptor along with IgM.
- Has the highest carbohydrate content among all the Igs, but its functions are unknown.
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Description
This quiz covers the basics of antibodies, also known as immunoglobulins, which are specialized glycoproteins produced by activated B cells in response to an antigen. Learn about their structure, function, and role in the immune system.
