B3: IMMUNE AND DEFENCE SYSTEMS

Question 1

What are the non-specific human defence systems?

Answer 1

-skin
-stomach acid
-mucus and cilia
-eyelashes
-tears

Question 2

How does the skin help to protect against pathogens?

Answer 2

-physical barrier
- stops microorganisms getting into the body
-platelets clot blood at wounds to prevent microorganisms from getting in
-sebum (chemical that breaks down bacteria)

Question 3

How does stomach acid help to protect against pathogens?

Answer 3

kills microorganisms

Question 4

How do mucus and cilia help to protect against pathogens?

Answer 4

-mucus traps pathogens
-cilia then beats mucus away
-this protects lungs

Question 5

How do eyelashes help to protect against pathogens?

Answer 5

-physical barrier
-prevents pathogens from getting into eyes

Question 6

How do tears help to protect against pathogens?

Answer 6

-chemical barrier
-enzyme in tears

Question 7

What is phagocytosis?

Answer 7

-white blood cell locates microorganism and pathogen binds to cell membrane of phagocyte
-a pit is formed on the cell membrane where the pathogen moves into the phagocyte
-phagocyte engulfs and digests pathogen with use of enzymes
-the end products diffuse into the white blood cell and are absorbed
-

Question 8

What do lymphocytes produce?

Answer 8

-antibodies
-antitoxins

Question 9

What are antibodies?

Answer 9

-proteins produced by lymphocytes that recognise pathogens and bind with antigens of pathogens, clumping them together for phagocytosis
-antibodies produced are specific to a type of antigen

Question 10

What are antitoxins?

Answer 10

-substances produced by the lymphocytes to neutralise toxins produced by pathogens

Question 11

What are memory cells?

Answer 11

-lymphocytes differentiate into memory cells
-they recognise antigens and an produce antibodies rapidly and in large concentrations to destroy pathogens before they cause symptoms
-this leads to immunity