IGCSE Biology

Describe the features of gas exchange surfaces in humans, limited to: large surface area, thin surface, good blood supply and good ventilation with air

Explain that the cholera bacterium produces a toxin that causes secretion of chloride ions into the small intestine, causing osmotic movement of water into the gut, causing diarrhoea, dehydration and loss of ions from the blood

Describe cholera as a disease caused by a bacterium which is transmitted in contaminated water

State that memory cells are not produced in passive immunity

Explain that passive immunity is a short-term defence against a pathogen by antibodies acquired from another individual, including across the placenta and in breast milk

Explain the role of vaccination in controlling the spread of diseases

Outline the process of vaccination: (a) weakened pathogens or their antigens are put into the body (b) the antigens stimulate an immune response by lymphocytes which produce antibodies (c) memory cells are produced that give long-term immunity

State that specific antibodies have complementary shapes which fit specific antigens

Describe antibodies as proteins that bind to antigens leading to direct destruction of pathogens or marking of pathogens for destruction by phagocytes

Describe active immunity as defence against a pathogen by antibody production in the body