2. Body defences

What is skin flora?

• Microscopic plants growing on the skin surface

• Dead skin cells on the surface

• Community of micro-organisms on the skin surface

• Pathogens on the skin surface

How do phagocytes defend the body against microbes?

• Ingest bacteria

• Produce antibodies

• Produce antitoxins

• Clot the blood

What is the role of skin flora?

• Ingest pathogens

• Produce antibodies

• Prevent pathogens becoming established

• Make the skin waterproof

Which component of the blood forms clots to seal a wound?

• Plasma

• Platelets

• Red blood cells

• White blood cells

What is an antigen?

• A protein produced by a lymphocyte

• A type of pathogen

• A protein on a pathogen that stimulates an immune response

• A protein produced by a phagocyte

What is the role of antibodies?

• To trigger an immune response

• To inactivate specific bacteria and viruses

• To neutralise toxins

• To ingest bacteria

Which blood cells are stimulated by the presence of antigens?

• Red blood cells

• White blood cells called phagocytes

• White blood cells called lymphocytes

What process has occurred to cell X in the diagram?

• Mitosis of the lymphocyte to produce clones

• Meiosis of the lymphocyte to produce clones

• Mitosis of the phagocyte to produce clones

• Meiosis of the phagocyte to produce clones

What is the role of antitoxins?

• To neutralise toxins produced by bacteria

• To neutralise toxins produced by viruses

• To inactivate bacteria by attaching to specific antigens

• To inactivate bacteria by attaching to the toxin

Which of the antibodies in the picture will inactivate the measles pathogen?

• A

• B

• C

• D