Immune System: Phagocytes and Lymphocytes

Question 1

what is a disease?

Answer 1

a condition that prevents the body or part of it working properly

Question 2

what causes diseases?

Answer 2

• micro-organisms (pathogens) entering the body and feeding and reproducing in it
• in doing so, they may damage the body or poison it by excreting toxic waste substances called toxins

Question 3

what are the main organisms that cause disease?

Answer 3

very small microorganisms - the skin and membranes of the body act as physical barriers to prevent them from entering, if the barriers become damaged then white blood cells take over the defence of the body

Question 4

what are the two main types of white blood cells?

Answer 4

phagocytes and lymphocytes

Question 5

what happens during phagocytosis?

Answer 5

1. phagocyte recognises pathogen
2. phagocyte engulfs pathogen in a process known as phagocytosis
3. the lysozymes containing enzymes more towards the pathogen
4. enzymes break down pathogen
5. useful materials are absorbed
6. waste products are removed from the phagocyte

Question 6

what are phagocytes?

Answer 6

a type of white blood cell that engulf and digest pathogen that they encounter

Question 7

what is the job of lymphocytes?

Answer 7

• they produce special Y shaped proteins called antibodies - these attach to proteins on the surface of pathogens called antigens
• each pathogen has a different shaped antigen so the lymphocytes need to make a specific complementary antibody
• lymphocytes allow organisms to build up an immunity towards certain diseases

Question 8

what is the process lymphocytes go through to kill pathogens?

Answer 8

1. lymphocytes detect pathogen’s antigens
2. lymphocyte identifies the correct type of antibody to make, which is complimentary to the pathogen’s antigen
3. lymphocyte releases large numbers of correct antibody
4. pathogens either clump together resulting in death or the antibodies trigger phagocytes - some pathogens can even burst
5. lymphocytes produce cells that produce lots of the antibody very quickly if they detect the same pathogen again - these are called memory cells

some antibodies are specialised to combat toxins, chemicals released by the pathogen which cause cell damage - they are called anti-toxins