5.1 and 5.2

Question 1

infection

Answer 1

interaction between pathogen and body’s defence mechanism

Question 2

immunity

Answer 2

body’s defences better prepared for second infection after overwhelming the pathogens before

Question 3

non-specific defence mechanism

Answer 3

general and immediate
e.g. skin forming barrier to entry of pathogens
phagocytosis

Question 4

specific defence mechanism

Answer 4

less rapid but longer lasting
e.g. cell-mediated responses with T lymphocytes
humoral responses with B lymphocytes

Question 5

recognising cells

Answer 5

lymphocytes must distinguish self(body cells and molecules) from non-self(foreign material)

Question 6

4 materials immune system can idenitfy

Answer 6

1. pathogens
2. non-self material(cells from other organisms of same species)
3. toxins
4. abnormal body cells(cancer)

Question 7

lymphocyte recognising self process in fetus

Answer 7

1. around 10mill different lymphocytes present, each capable of recognising diff chemical shape
2. in fetus, these lymphocytes are constantly colliding with other cells
3. infection in fetus is rare because is protected from outside by mother and placenta
4. lymphs will only collide exclusively with body’s own material
5. some of lymphs will have receptors that excactly fit those of body’s own cells
6. these lymphs will either die or are supressed
7. remaining lymphs are those that might fit foreign material and so only respond to non-self

Question 8

lymphocyte recognising self process in adult

Answer 8

1. around 10mill different lymphocytes present, each capable of recognising diff chemical shape
2. lymphs produced in bone marrow only encounter self-antigens
3. any lymphs that show immune response to self-antigens undergo programmed cell death(apoptosis) before they differentiate into mature lymphs
4. no clones of anti-self lymphs will appear in blood, leaving only those that might respond to non-self

Question 9

phagocytosis

Answer 9

1. chemical products of pathogens or dead, damaged and abnormal cells act as attractants, causing phagocytes to move towards pathogen
2. phagocytes have several receptors on cell-surface membrane that recognise and attach to chemicals on surface of pathogen
3. engulf pathogen to form a vesicle- phagosome
4. lysosomes move towards vesicle and fuse with it
5. lysozome enzymes in lysosome destroy ingested bacteria by hydrolysis of their cell walls
6. soluble products from breakdown of pathogen are absorbed into cytoplasm of phagocyte