Notes

Core
• Define pathogen as a disease-causing organism
• Define transmissible disease as a disease in
which the pathogen can be passed from one
host to another
• State that the pathogen for a transmissible
disease may be transmitted either through
direct contact, e.g. through blood or other body
fluids, or indirectly, e.g. from contaminated
surfaces or food, from animals, or from the air
• State that the body has defences:
– mechanical barriers, limited to skin and
hairs in the nose
– chemical barriers, limited to mucus and
stomach acid
– cells, limited to phagocytosis and antibody
production by white blood cells
– which can be enhanced by vaccination

Supplement
• State that antibodies lock on to antigens
leading to direct destruction of pathogens,
or marking of pathogens for destruction by
phagocytes
• Explain how each pathogen has its own
antigens, which have specific shapes, so
specific antibodies which fit the specific shapes
of the antigens are needed
• Define active immunity as defence against a
pathogen by antibody production in the body
• Explain that active immunity is gained after an
infection by a pathogen, or by vaccination
• Explain the process of vaccination:
– harmless pathogen given which has
antigens
– antigens trigger an immune response by
lymphocytes which produce antibodies
– memory cells are produced that give
long-term immunity