Human Defence Systems AQA GCSE Biology

what is an antigen?

a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies

what's an antibody?

An antibody is a protein made by lymphocytes that is complementary to an antigen and, when attached, clumps them together and signals the cells they are on for destruction

what's an antitoxin?

An antitoxin is a protein/chemical produced by WBC that can bind and counteract the toxins that pathogens produce

How does the skin protect the body from disease?

acts as a physical barrier, helpful good bacteria live on the skin providing competition for pathogens, secretes oils/antimicrobial substances which kill pathogens

How do tears defend against infection?

there are enzymes in tears(called lysozymes)

how does the trachea defend against infection?

lined with a layer of mucus via goblet cells that traps particles, also lined with cilia which are tiny hair like structures they move mucus and trapped particles up to the back of the throat to either be swallowed and killed by stomach acid or spat out

How does the stomach defend against infection?

contains hydrochloric acid that kills pathogens

How does the nose defend against pathogens?

The nose has cilia and mucus which trap particles that could contain pathogens.

What do lymphocytes do?

produce antibodies

What are phagocytes and what do they do?

a type of white blood cell that via phagocytosis they track the pathogen, bind to it and engulf it and destroy it via enzymes within it

how do antibodies work? ( 6)

- they lock onto a foreign antigen and act as a signal for phagocytes to come and destroy them,

- the shape of each antibody is specific to the antigen

- once our immune system knows which shape the antibody has to take to bind to the antigen, memory cells in our immune system remember this for next time so the immune system can produce antibodies quicker and can get rid of the pathogen before it affects our body (immunity)

- Furthermore, the binding of antibodies to antigens causes pathogens to clump together making them easier to destroy