B1.1.2 How our bodies defend themselves against infection diseases

All the information you'll need, taken directly from the specification.



Pathogens are microbes that cause diseases.

The three types are bacteria, virus and fungus.

They produce toxins - the symptoms that make us ill.

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Viruses inject into our cells. When our cells reproduce, the virus is also reproduced. The virus then breaks out, killing ther cells in doing so. We cannot treat viruses with antibiotics because killing the virus would kill the cells.

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Alexander Fleming

Alexander Fleming grew bacteria on an agar plate while on holiday. When he came back, mould had grown, but there was a clear ring of jelly around it - something had killed the bacteria.He extracted penicillin, the first antibiotic, but it wouldn't keep, so he gave up. 10 years later, Ernest Chain and Howard Flory found a way to produce it on a large scale.

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Antibiotics kill bacteria in the body which causes diseases. They destroys the bacteria but not our cells. They cure diseases like plagua and TB, but have no effect on viruses.

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Defence Barriers

  • Mucus/ lining of airway
  • Skin/scabs
  • Stomach acid
  • White Blood Cells
    • They ingest pathogens
    • They produce antibodies to destroy each type of pathogen
    • they produce antitoxins to neutralise the toxins which make us ill
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Dead or inactive pathogens are injected into the body. Your body produces antibodies for this pathogen, so that if you contract the pathogen in the future your body can produce antibodies again rapidly.

MMR vaccine - used to provide immunity against measles, mumps and rubella. It was linked to autism but this was later proved to be false.

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Semmelweiss discovered mothers and babies were more likely to die if delivered by doctors than midwives.This was because most doctors came straight from examining dead bodies. He encouraged doctors to wash their hands between patients, and this can be put into contact today.

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The Aseptic Technique

Make sterile agar in petri dish.

Flame innocculating loop

Flame sample bottle

Seal dish and incubate at 25 C

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Antibiotic resistance

Antibiotic resistance is caused by overuse and inappropriate use of antibiotics. If a strain of resistant bacteria develops it will spread rapidly because there is less effective treatment.

MRSA is resistant to the antibiotic methicillin. This means it spreads easily and is a problem in hospitals.

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This is really good, it helped me a lot! 

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