section 1: disease & the immune system - topic 4: antibodies Flashcards
what kind of protein are antibodies?
glycoproteins.
what are glycoproteins?
proteins with a carbohydrate group attached.
what are antibodies made of?
4 polypeptide chains.
- 2 heavy chains.
- 2 light chains.
what does each chain of an antibody have?
a variable region.
a constant region.
what do the variable regions of the antibody form?
the antigen-binding sites.
what is specific about the shape of the variable region?
it is complementary to a particular antigen.
do variable regions differ between antibodies?
yes.
what does the hinge region allow?
allows flexibility when the antibody binds to the antigen.
what do the constant regions allow?
binding to receptors on immune system cells i.e. phagocytes.
do the constant regions differ between antibodies?
no.
what holds the polypeptide chains of the protein together?
disulphide bridges.
what 3 ways do antibodies help in clearing an infection.
- agglutinating pathogens.
- neutralising toxins.
- preventing the pathogen binding to human cells.
how do antibodies agglutinate pathogens?
- each antibody has 2 sites, so it can bind to 2 pathogens at the same time.
^ the pathogens become clumped together. - phagocytes then bind to the antibodies and phagocytose a lot of pathogens all at once.
antibodies that behave this way are known as agglutinins.
how do antibodies prevent pathogens from binding to human cells?
when antibodies bind to the antigens on pathogens, they may block the cell-surface receptors that the pathogens need to bind to the host cells.
^ this means the pathogen can’t attach to or infect the host cells.
how do antibodies neutralise toxins?
like antigens, toxins have different shapes.
- antibodies called anti-toxins can bind to the toxins produced by the pathogens.
- this prevents the toxins from affecting human cells, so the toxins are neutralised.
- the toxin-antibody complexes are also phagocytosed.
