Antibodies Flashcards
Antibodies
Y shaped glycoproteins called immunoglobulins
What are antibodies made of ?
Two identical polypeptide chains called heavy chains and light chains
What are the chains held together by ?
Disulfide bridges within the chains and within the polypeptide chains holding them together
What are antibodies produced by ?
B-lymphocytes
Structure of antibodies
Quaternary
What 2 regions do each polypeptide chain have ?
- constant region
- variable region
Hinge region
Provides the molecule with flexibility allowing it to bind two separate antigens one at each of its antigen- binding site
Antibody binds to an antigen
Antigen-antibody complex
Is the amino acid sequence in the variable regions of the antibodies the same or different ?
Different
Variable region
Where the antibody attaches to the antigen to form an antigen-antibody complex
What is at the end of a variable region ?
Antigen-binding site
How many amino acids Is each antigen-binding site composed of ?
110-130 amino acids
Epitope
The part of the antigen that bids to the antibody
What can antibodies act as ?
Anti-toxins
Opsonins
Agglutinins
How do antibodies defend the body ?
- Antibody of the antigen-antibody complex acts as an opsonin thus complex is easily engulfed and digested by phagocytes
- Most pathogens can no longer effectively invade the host cells once they are part of an antigen-antibody complex
- Antibodies act as agglutinins causing pathogens carrying antigen-antibody complexes to dump together —> helps prevent them spreading through the body and makes it easier for phagocytes to engulf a number of pathogens at the same time
- Antibodies act as anti-toxins binding to the toxins produced by pathogens and making them harmless
Opsonins
Bind to the pathogen and then act as binding sites for phagocytic cells ( facilitating phagocytosis )
Agglutinins
Clump pathogens together by binding antigens to both binding sites and then cross linking them
Anti-toxins
Bind to molecules released by pathogens and make them harmless to the organism
Neutralisation
When an opsonin binds to pathogen but prevents attachment of the pathogen to the host cell
