Defending against infection

Info on pathogens. white blood cells etc.

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  • Created on: 10-04-11 14:43
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Defending against infection
Pathogens are microorganisms such as bacteria and viruses
that cause disease. Bacteria release toxins, and viruses damage
our cells. White blood cells can ingest and destroy pathogens.
They can produce antibodies to destroy pathogens, and
antitoxins to neutralise toxins.
In vaccination pathogens are introduced into the body in a
weakened form. The process causes the body to produce
enough white blood cells to protect itself against the pathogens,
while not getting diseased.
Antibiotics are effective against bacteria, but not against viruses.
Some strains of bacteria are resistant to antibiotics.
Pathogens bacteria
Pathogens are microorganisms that cause infectious disease.
Bacteria and viruses are the main pathogens.
Bacteria are microscopic organisms. They come in many shapes and
sizes, but even the largest are only 10 micrometres long 10 millionths
of a metre.
Bacteria are living cells and, in favourable conditions, can multiply
rapidly. 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
Pathogens viruses
Viruses are many times smaller than bacteria [bacteria: Singlecelled
microorganisms, some of which are pathogenic in humans, animals

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Singular is bacterium. ]. They are among the smallest
organisms known and consist of a fragment of genetic material inside a
protective protein coat.
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.…read more

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White blood cells can:
ingest pathogens and destroy them
produce antibodies to destroy pathogens
produce antitoxins that neutralise the toxins released by pathogens
In a written examination, it is easy to get carried away and waffle on
about things such as invaders and battles, but stick to the point.…read more

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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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Vaccines in early childhood can give protection against many serious
diseases. Sometimes more than one vaccine is given at a time, like the
MMR triple vaccine against mumps, measles and rubella.
Sometimes vaccine boosters are needed, because the immune
response 'memory' weakens over time. Antitetanus injections may
need to be repeated every ten years.
Antibiotics are substances that kill bacteria [bacteria: Singlecelled
microorganisms, some of which are pathogenic in humans, animals
and plants. Singular is bacterium. ] or stop their growth.…read more

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Since the discovery of penicillin, many other antibiotics have been
discovered or developed. Most antibiotics used in medicine have been
altered chemically to make them more effective and safer for humans.
Bacterial strains can develop resistance to antibiotics. This happens
because of natural selection. In a large population of bacteria
[bacteria: Singlecelled microorganisms, some of which are
pathogenic in humans, animals and plants. Singular is bacterium. ],
there may be some cells that are not affected by the antibiotic.…read more


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