Immunology 2: Antibody Structure Flashcards
(58 cards)
What is an antibody?
the secreted effector molecules of B/plasma cells that bind to specific ligands on surfaces of pathogen; then serves as the ligand for phagocyte receptors
All antibodies have a common core structure that consists of what?
2 identical light chains and 2 identical heavy chains; the heavy chains are attached to each other and each light chain is attached to a heavy chain
What is an immunoglobulin domain?
a sequence of amino acids in an antibody sequence, about 110 residues long; can be either a variable and constant domain
The unique tertiary structure of antibodies enables them to do what?
withstand highly variable and potentially destabilizing extracellular conditions while maintaining functionality in the presence of infection
What is the primary difference between the structure of the C and V domains of immunoglobulin domains?
V domains are larger and have extra loops of polypeptide chain
What is common to the structures of both C and V Ig domains?
they are roughly cylindrical in shape; formed by 2 adjacent beta sheet structures linked by an intrachain disulfide bond
What is an immunoglobulin?
the antigen-binding molecule (effector molecule) of B cells; termed antibody once secreted
The two identical heavy chains in an antibody monomer are joined together by ____ bonds.
disulfide
The V domains of heavy chains are adjacent to the V domains of light chains and form what?
the variable domains come together to form the unique antigen binding site of of each antibody molecule; this makes 2 antigen binding domains in each monomer
What is the significance of the carboxy terminus of the heavy chains of the antibody monomer?
they bind to antibody receptors, or Fc receptors, expressed on the surface of immune cells; this is one way the antibody bridges the innate and acquired immune systems
Hypervariable regions of both heavy and light chain V domains are located alongside low variability regions known as ____.
Framework (FR) regions
Framework regions of V domains form _____ that provide the structural framework of the domains while hypervariable sequences form _____ that correspond to the loops between beta sheets.
beta-sheets; loops
What is the complementarity-determining region?
this is the hypervariable site of a V domain within an antibody that serves as the antigen-binding site
What is an antigenic determinant, or epitope?
the portion of any particular antigen that an antibody binds to. Typically composed of glycoproteins, polysaccharides, glycolipids and proteoglycans.
What is a multivalent antigen?
pathogenic molecule that has more than one epitope and can be bound by multiple antibodies; these multiple epitopes can be repeating or distinct
Most antibodies have specificity for what types of chemical structures?
carbohydrates or proteins
Binding of antibodies to antigens is based solely on non-_____ forces.
based on non-covalent forces (electrostatic, van der Waals, H-bonding, hydrophobic interactions)
What determines binding affinity of an antibody binding to its antigenic determinant?
the binding strength of the antibody to antigenic determinant
To what does binding avidity refer?
the combined strength of all antigen binding domains of an antibody bound to its antigenic determinant simultaneously
A continuous epitope is formed by what?
a continuous, linear stretch of amino acids found on an antigen
A discontinuous epitope is formed by what?
portions of an antigen that come together to form a discreet formation; ex: amino acids in a protein antigen are adjacent when the protein is in its native form
Antibodies can be divided into ____ different isotypes based on the type of ____ _____ that is found in the antibody.
5; heavy chain
What is the hinge region of the heavy chain?
region of IgG, IgD, and IgA heavy chains that is rich in proline residues; allows flexibility of the antibody molecule in order that it may bind more easily to antigenic determinants or immune components
What are the 5 types of heavy chains?
Ig A, D, E, G, M (greek letters though)
