Download Microbes

23/05/2017
Microbes and Disease
W Richards
The Weald School
Microbes
23/05/2017
Microbes are micro organisms that are too small to be seen. A
pathogen is a microbe that can cause diseases if it enters the
body:
They can be
breathed in
through the
mouth or nose
…or other
natural
openings…
They can be
ingested (eaten)
through the mouth
They can enter
through cuts or
bites in the skin or
just by touching
something
Microbes: our defence against them
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Our bodies have many defence mechanisms against invading
microbes:
The skin acts
as a barrier
Stomach produces
stomach acid
If our skin is cut
platelets seal the
wound by clotting
Tears contain an
enzyme that kills
bacteria
The breathing
organs produce
mucus to cover the
lining of these
organs and trap the
microbes
Disease
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A disease is any condition where the body isn’t working as it should. This
could be caused by a malfunction in the body (as with diabetes), or it could
be caused by the two types of MICROBE:
Bacteria
Viruses
•1/1000th mm big
•1/1,000,000th mm big
•Living cells (some are harmless)
•Genetic info inside a protein coat
•Grow very quickly
•Not affected by antibiotics
•Affected by antibiotics
•Release poisons
•Examples: food poisoning,
tetanus, sore throats
•Examples: colds, flu, polio,
chicken pox
Fungi
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Fungi are another form of microbe. There are many
different varieties ranging from bread mould to mushrooms.
Fighting disease
If microbes do enter our body they need to
be neutralised or killed. This is done by
WHITE BLOOD CELLS:
White blood cells do 3 things:
1) They eat the microbe
2) They produce antibodies to
neutralise the microbe
3) The produce antitoxins to
neutralise the poisons produced
by microbes
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Producing antibodies
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You’re going
down
Step 1: The white blood cell “sees”
the antigen (microbe)
Step 2: The cell produces
antibodies to “fit” the antigen
Step 3: The antibodies fit onto the
antigens and cause them to “clump”
Step 4: The antigens are “eaten”
by the white blood cells
Fighting disease
NATURAL IMMUNITY
This is when antibodies are produced
by a person when needed or they are
passed on by the mother during
pregnancy.
ARTIFICIAL IMMUNITY
A vaccine with dead microbes is injected
– the body is “tricked” into producing
antibodies ready for the real thing. This
is called PASSIVE IMMUNISATION
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Using Antibiotics
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Antibiotics can be used to kill bacteria. However, there are
two problems:
1) Overuse of antibiotics can lead to
bacteria becoming resistant
2) Antibiotics have no effect on a
virus, like the common cold. A virus
must be allowed to “run its course”.