Defences against pathogens
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Defences against Pathogens . Causes of illness.  There are four main ways pathogens enter your body : . Pathogens.  Pathogens, such as Bacteria, viruses and fungi are invaders causing disease and illness. Your body provides the perfect environment for them to reproduce.

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Causes of illness
Causes of illness

 There are four main ways pathogens enter your body :


 Pathogens, such as Bacteria, viruses and fungi

are invaders causing disease and illness. Your body provides the perfect environment for them to reproduce.

  • Bacteria produces toxins (poison) that makes you ill.

  • To prevent against pathogens you might get a vaccination, i.e. introducing a small amount of a dead or inactive disease because you will then build immunity to it.

The body s defences
The Body’s Defences

  • The Body has tiny hairs, called cillia, along the respiratory track that moves mucus which traps microbes from the breathing system.

  • And you also the largest muscle in your body, your skin that acts like a barrier stopping pathogens getting into your body.

White blood cells vs pathogens
White Blood Cells vs. Pathogens

  • When undesirable microbes enter your body you are providing the right living conditions for them to reproduce.

  • The white blood cells can kill the pathogens in three different ways:

  • By surrounding the pathogen and ingesting it to then slowly kill it.

  • Microbes have antigens on the outside of their cell, white blood cells can produce anti bodies that shapes to fit onto the antigens therefore stopping them producing toxins.

  • Another job of the white blood cell is to produce antitoxins that neutralise the toxins produce by bacteria.

White blood cells defences
White blood cells defences

  • When the antibodies fit onto the antigens, this stops pathogens producing toxins which can be very harmful.

  • That is why the white blood cells produce antitoxins to cancel out the poison.

Immunity from diseases
Immunity from diseases

  • Once you get a disease or illness you are unlikely to have it again.

  • Because your immunity system remembers the shape of the antigens, on the cell of the pathogen, therefore will produce the right antibodies.

  • If your body does not recognise the antigens it will have to do trial and error, when it takes to much time this is when you start feeling ill.


 Antibiotics are only use to fight bacteria because viruses reproduce by take over the host cell and then bursting it open to spread the infection, and using antibiotics would damage the cell.

  • There are some bacteria that have a stronger immunity, and if you do not finish a course of antibiotics the bacteria that is resistant will reproduce. And then can mutate so that they are resistant to antibiotics causing illnesses, such as MRSA, that can not cured.

  • This is why doctors do not prescribe antibiotics very often.


  • Penicillin was first discovered by Alexander Fleming after leaving a few Petri dishes with bacteria on them, in his lab during the two weeks he was on holiday. He then noticed a halo surrounding the mould that contaminated the plate. Alexander Fleming discovered that the antibacterial substance was not developed by all moulds, only by PenicilliumNotanum.

The development of penicillin
The Development of Penicillin

 Two scientist, by the names of Howard Florey and Ernst Chain also know as Florey and Chain, found Fleming’s work and did more research to see if they could isolate penicillin making it into a drug to treat patients. Because of the War it was hard to find anyone that could help them with mass production so they went to America.

Vaccinations can be scary
Vaccinations, Can be scary...

 People can build immunity against diseases by introducing a small amount of a dead or inactive pathogen in to their bodies, this is mostly done through jabs. The vaccine will stimulate your white blood cell fight the pathogen and your immunity system will remember the disease therefore giving you immunity in the future.

Growing microbes
Growing Microbes

  • The perfect conditions to grow microbes areat room temperature around about 25 degrees Celsius, because if you grow them at 37 degrees being the body temperature will we probably grow harmful bacteria. You would also need to grow them on agar jelly because the jelly provides nutrients for them to grow.

  • To make the experiment fair you need an dependant, independent and controlled variables.