1. 30/11/2018
Microbes and Disease

2. 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…

3. 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

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

5. 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

6. 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

7. 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

8. 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

9. 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”.