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Defending against
infection…read more

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Pathogens are micro organisms- bacteria and viruses. the pathogens
are not the disease - they cause the disease
Bacteria ­ Realise toxins. Once inside the body, they release
poisons or toxins that make us feel ill. Diseases caused by
bacteria include:
food poisoning
whooping cough
gonorrhoea - a sexually transmitted disease…read more

Slide 3

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Virus- damage cells. Smaller than bacteria. Viruses can only
reproduce inside host cells, and they damage the cell when they do
this. A virus can get inside a cell and, once there, take over and make
hundreds of thousands of copies of itself. Eventually the virus copies
fill the whole host cell and burst it open. The viruses are then passed
out in the bloodstream, the airways, or by other routes.
Diseases caused by viruses include:
influenza - flu
chicken pox
AIDS…read more

Slide 4

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White blood cells
White blood cells can:
Ingest pathogen and destroy them
Produce antibodies to destroy pathogens
produce antitoxins that neutralise the toxins
released by pathogens
antibodies and antitoxins are not living
things - they are specialised proteins…read more

Slide 5

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Types of white blood cells
Phagocytes can easily pass through blood vessel
walls into the surrounding tissue and move
towards pathogens or toxins. They then either:
ingest and absorb the pathogens or toxins
release an enzyme to destroy them
Having absorbed a pathogen, the phagocytes may
also send out chemical messages that help nearby
lymphocytes to identify the type of antibody
needed to neutralise them.…read more

Slide 6

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Pathogens contain certain chemicals that are
foreign to the body and are called antigens. Each
lymphocyte carries a specific type of antibody - a
protein that has a chemical 'fit' to a certain
antigen. When a lymphocyte with the
appropriate antibody meets the antigen, the
lymphocyte reproduces quickly, and makes many
copies of the antibody that neutralises the
pathogen.…read more

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