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| Questão | Responda |
| What is the antibodies made up of (on the molecular level)? | Made up of chains of amino acid monomers linked by peptide bonds (proteins) |
| Describe the structure of an antibody |
Variable regions
Hinge regions
Constant regions
Disulphide bridges
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Image (binary/octet-stream)
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| What is the variable region? | Variable regions form the antigen-binding sites. The shape of the variable region is complementary to a particular antigen - they differ between antibodies |
| What is the hinge region? | The hinge region allows flexibility when the antibody binds to the antigen |
| What is the constant region? | The constant regions allow binding to receptors on immune system cells (e.g. phagocytes). The constant region is the same (i.e. it has the same sequence of amino acids) in all antibodies |
| What is the role of the disulphide bridges in antibodies? | Disulphide bridges hold the polypeptide chains of the protein together |
| What are the roles of antibodies? | Agglutinating pathogens Neutralising toxins Preventing the pathogen binding to human cells |
| How do antigens agglutinate pathogens? | Each antibody has two binding sites, so an antibody can bind to two 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 in this way are known as agglutinins |
| How do antibodies neutralise toxins? | Like antigens, toxins have different shapes. Antibodies called anti-toxins can bind to toxins produced by pathogens. This prevents toxins from affecting human cells, so the toxins are neutralised (inactivated). The toxin-antibody complexes are also phagocytosed |
| How do antibodies prevent pathogens 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 cannot attach to or infect the host cells |
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