What is the difference between non-specific and specific defences against pathogens?

Non-specific defences work against any type of pathogen (e.g. any species of fungi or bacteria).


Specific defences are specific to a particular pathogen (or antigen).

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Name 4 non-specific defences that prevent pathogens from entering the body.

  1. Skin (and the oils it secretes).


  1. Stomach acid.


  1. Hairs and mucus in airways.


  1. Tears in eyes. 

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How does the skin act as a defence against pathogens?

1It covers the body, physically preventing pathogens from entering.


2It secretes oils and antimicrobial substances that kill pathogens.

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How does the stomach act as a defence against pathogens?

It produces stomach acid (hydrochloric acid), which creates a very low pH that destroys pathogens. 

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How do the trachea and bronchi act as a defence against pathogens?

Some of the cells that line the trachea and bronchi produce mucus which traps pathogens.


Other cells have tiny hair-like projections called 'cilia' that help to move the mucus and pathogens out of the lungs.

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What is the role of the immune system? 

To locate and destroy pathogens that enter the body.

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What type of cells help to defend against pathogens and are part of the immune system?

White blood cells.

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What are the 3 main functions of white blood cells?

1Phagocytosis.


2Producing antibodies.


3Producing antitoxins.

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What is phagocytosis (in one sentence)?

Phagocytosis is the process by which a phagocyte engulfs and destroys a pathogen (or a cell that contains a pathogen). 

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What are the steps of phagocytosis?

Phagocytosis is carried out by a special type of white blood cell called a phagocyte.


  1. First, the phagocyte tracks down a pathogen and binds to it.
  2. The phagocyte's membrane will then surround the pathogen and engulf it.
  3. Finally, enzymes inside the phagocyte break down the pathogen in order to destroy it.

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What's the difference between antigens and antibodies?

An antigen is any substance that your body sees as foreign, which then causes your immune system to produce antibodies against it. For example, the toxins and cell walls of pathogens would be considered antigens.


An antibody on the other hand is a protein produced by our white blood cells that binds to specific antigens. This acts as a signal to our immune system to destroy the antigen (or the pathogen it is part of).

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What are antitoxins?

Antitoxins are small proteins produced by white blood cells that bind and neutralise the toxins produced by bacteria.

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What do antibodies bind to?

Antibodies bind to antigens that have a complementary shape.

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