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Biology 2 ­ Keeping Healthy
GCSE Level
OCR 21st Century Science
By Izzie Sims…read more

Slide 2

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Lots of micro-organisms cause diseases. This type of micro-organism is called a
pathogen. They include bacteria, fungi and viruses. The best conditions for micro-
organisms to reproduce are in warm, moist places such as the human body. In
ideal conditions, one micro-organism can reproduce every twenty minutes. Once
pathogens start reproducing they cause an infection. The effect that the infection
has on the body is called a symptom. For example malaria causes flu ­ like
symptoms which affect your body's cells. Other micro-organisms produce toxins
that cause fevers.
Your body has barriers to keep micro-
organisms out. Your skin keeps out
micro-organisms and your tears have
enzymes that destroy bacteria. If any do
get into your body through food or drink
your stomach acid will kill them.…read more

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Immune System
Your immune system is what deals with any MO's that do get into your body.
White blood cells recognise foreign bodies. They can then engulf and digest
the microbes. This process is called phagocytosis.
White Blood Cell…read more

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Immune System
A different sort of white blood attacks specific MO's. MO's make antigens. An
antigen is a substance that triggers immune responses. The white blood cells
recognise the antigens and produce antibodies. Each antibody is specific to
one particular antigen. The antibodies latch onto the invading MO's and mark
them so that other white blood cells can digest them. When the right white
blood cell recognises the antigens on the MO's it divides to make more
identical cells which make lots more antibodies to fight the infection. The next
time you get the infection you are able to fight it off much quicker because
some of the antibodies stay in your blood stream.…read more

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A small amount of dead or inactive
micro organisms are injected into
you. Because they still carry
antigens, your white blood cells
recognise them You
andare vaccinated against some diseases, like
antibodies to attack when
them, butyou
youare young. A vaccination
don't get ill. If means
you everthat you
get thebecome immune to the disease.
disease for real, This is how
your a vaccination
white blood works...
cells recognise it and kill it off
quickly with the antibodies they
made when you were immunised.
So your body will get rid of the
disease before you get sick.…read more

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Vaccination ­ For or Against?
You need to be able to look at both sides of an argument. This brings in morals
and ethics.
Some people choose not to If most of the population
have their child vaccinated are vaccinated against a
because they are worried disease there is less
about possible side effects. chance of an epidemic
For example there was a breaking out. Also,
scare a while ago about the diseases such as small
MMR (Mumps, measles and pox have almost been
rubella) vaccine causing wiped out by vaccination
autism. Vaccination are never programs. Some people
completely safe for an believe that it is better to
individual because different risk a bad reaction then
people may have different become very ill from an
reactions to the vaccination. otherwise preventable
Some parents prefer to disease.
eliminate this risk by refusing
to get their child immunised.…read more

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