defense against disease

notes on defense against disease AQA unit 4.1 to 4.7

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  • Created on: 25-02-12 18:38
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Defence against disease
What causes disease
What the body does to catch a disease
How we can artificially protect the body from a disease it may catch in the future
Medicines and antibiotics
A microorganism ­ a group of living things (bacteria, viruses and fungi)
How do these things cause disease?
The microorganisms that cause disease are called pathogens and these are the ones we
worry about. Bacteria cause disease by producing toxins (these are poisonous). Viruses
work in a different way (and are much much smaller than a bacteria), and they cause
disease by going up to a body cell, and infect them. They get inside them and reproduce
inside it, they reproduce so many copies of themselves the cell will break open/pop. This
makes the cell permanently damaged or destroyed. On the surface of any pathogen there are
antigens which have a specific shape.
How does the body defend itself from these pathogens?
The white blood cells are a way of defence, they work in three ways, they can ingest
pathogens, they can produce antibodies or they can produce antitoxins. White blood cells
are slightly bigger than red blood cells.
Ingesting pathogens
A virus has invaded the body, the white blood cell then recognises that there is something
that is not quite right, it then moves towards to the problem (the virus) and consumes it, like a
ball sinking into sinking sand (the ball being the virus). The white blood cell basically eats it,
once the white blood cell has eaten the virus it produces enzymes to break down the virus.
On the surface of any pathogen there are antigens which have a specific shape. The white
blood cells produce antibodies which are the same shape as the antigens, it takes a little
while for this to be worked out but once it is done the body produces many of these
antibodies and they eventually kill the pathogens.
Antitoxins are sent out by the white blood cells and the antitoxins go to the toxins and make
the toxins harmless/they deactivate them.

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How can we protect the body from a future infection?
Many people have vaccinations as a child, then you have more as you grow up against many
viruses or bacteria. In the vaccine there is a version/copy of a pathogen that are very harmful,
the pathogens are dead but it still has the antigens! The body produces antibodies to kill the
dead pathogens.…read more

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DNA which affects the genes.…read more


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