5.1 Cell recognition and the immune system

Question 1

Define pathogen

Answer 1

An infectious organism which spreads communicable diseases

Question 2

Define non-specific defence mechanisms and give two examples

Answer 2

Response is immediate and the same for all pathogens eg. physical skin barrier and phagocytosis

Question 3

Define specific defence mechanisms and give two examples

Answer 3

Response is slower and specific to each pathogen eg. cell mediated response and humoral response

Question 4

What do the protein molecules on the surface of cells help to identify?

Answer 4

-Pathogens
-Non-self material
-Toxins
- Abnormal body cells

Question 5

How do lymphocytes recognise cells belonging to the body?

Answer 5

• Lymphocytes that have receptors which bind to self cells are destroyed or suppressed
  -This leaves no lymphocytes that can bind to self cells and so lymphocytes only respond to foreign material

Question 6

After a pathogen gains entry to the. body it is often a number of days before the body’s immune system begins to control it. Suggest a possible reason why this is so.

Answer 6

A specific mechanism distinguishes between different pathogens but responds more slowly than a non-specific mechanism.