the immune system

Question 1

student used sterilised pipette to transfer E.coli into each culture, suggest why number of E.coli cells in each culture might have been lower if student had not used a sterilised pipette (2)

Answer 1

• unknown bacteria introduced
• these bacteria use food and space

Question 2

explain how a fetus is protected against pathogens that infect it’s mother during pregnancy (3)

Answer 2

• antibodies from mother are complementary
• to pathogens crossing the placenta
• giving passive immunity in fetus

Question 3

suggest why there has been a recent increase in number of children catching measles (1)

Answer 3

reduced vaccination in children

Question 4

explain why giving children more than one tetanus vaccination develops good immunity against tetanus (2)

Answer 4

• more memory cells
• higher concentration of antibodies