Unit 11
Disease and immunity.
Pathogens and the body's defence: viruses, why antibiotics miss them, the immune response, vaccines, and epidemics.
Before this unit
- Body systems
- Exponents and logarithms Mathematics
The unit, lesson by lesson
Lessons
4 lessons · 24 practice questions · about 2 hours
Viruses
Pathogens that are not cells: what is inside a virus, how small it is, how it takes over a cell, why antibiotics cannot touch it, and how fast viruses multiply.
The immune response
A first meeting with a virus: how fast it multiplies, what antibodies are, why the virus peaks before they rise, and how many days you feel ill.
Vaccines and immune memory
A second meeting with the same virus: memory cells, a vaccine from last month and from ten years ago, how low the virus stays, and how many antibodies a secondary response makes.
Epidemics and the SIR model
How a disease spreads through a crowd: exponential growth over generations of infection, the basic and effective reproduction numbers, the herd-immunity threshold, measles, and why vaccination also protects the unvaccinated.