30/11/2018 Microbes and Disease W Richards Worthing High School

Microbes 30/11/2018 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 They can be ingested (eaten) through the mouth They can enter through cuts or bites in the skin or just by touching something …or other natural openings…

Disease 30/11/2018 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 Living cells (some are harmless) Grow very quickly Affected by antibiotics Examples: food poisoning, tetanus, sore throats 1/1,000,000th mm big Genetic info inside a protein coat Not affected by antibiotics Release poisons Examples: colds, flu, polio, chicken pox

Fungi 30/11/2018 Fungi are another form of microbe. There are many different varieties ranging from bread mould to mushrooms.

Microbes: our defence against them 30/11/2018 Our bodies have many defence mechanisms against invading microbes: Tears contain an enzyme that kills bacteria The skin acts as a barrier The breathing organs produce mucus to cover the lining of these organs and trap the microbes Stomach produces stomach acid If our skin is cut platelets seal the wound by clotting

Fighting disease 30/11/2018 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: They eat the microbe They produce antibodies to neutralise the microbe The produce antitoxins to neutralise the poisons produced by microbes

Producing antibodies You’re going down 30/11/2018 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 30/11/2018 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

Using Antibiotics 30/11/2018 Antibiotics can be used to kill bacteria. However, there are two problems: Overuse of antibiotics can lead to bacteria becoming resistant Antibiotics have no effect on a virus, like the common cold. A virus must be allowed to “run its course”.