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Microbes · Chapter 9: Antibiotics and resistance

Year 11 SCX · About 16 minutes with activities · Turn your sound on

Chapter 9 · Antibiotics and resistance
Clear zoneantibiotic works
No clear zonebacteria grow anyway
Resistant strainselected, not made
Penicilliuma mould
Clear zonebacteria killed
Cell wall synthesis1 · inhibited
RNA synthesis4 · inhibited
Protein synthesis2 · inhibited
DNA replication3 · inhibited
Human cellno cell wall
Bacteriumthe target
Virusnot a cell
Resistantcan't be killed
Random mutationa change in the DNA
Some mutateda few resistant
Antibiotic addedsensitive killed
Resistant multiplyless competition
Resistance sharedpassed to others
Sensitivekilled quickly
Strongermore resistant alleles
Resistantantibiotic can't kill
MRSAStaphylococcus aureus
MDR-TBtuberculosis
Antisepticskin and cuts
Disinfectantsurfaces only
Antibioticinside the body

Chapter 9 recap

  • Antibiotics: chemicals produced by fungi that kill or inhibit the reproduction and growth of bacteria. Four ways: inhibit cell wall synthesis, protein synthesis, DNA replication, RNA synthesis. No effect on viruses.
  • Resistance: a random mutation creates variation; the antibiotic kills sensitive bacteria (selected against); resistant ones survive (selected for), reproduce and pass on their alleles.
  • Use them well: finish the course, only for bacterial infections, rest, don’t overuse in animals. MRSA and MDR-TB. Antiseptics: skin. Disinfectants: surfaces. Antibiotics: inside the body.
  • Next: Chapter 10 · The first and second lines of defence

How did a medicine stop working?

Chapter 9 · About 16 minutes · sound on

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