Antibiotics and antibiotic resistance
Introduced| English | Meaning |
|---|---|
| antibiotic/ˌæntɪbaɪˈɒtɪk/ | A medicine that kills bacteria or inhibits their growth. |
| resistant/rɪˈzɪstənt/ | resistant |
| penicillin/ˌpenɪˈsɪlɪn/ | An antibiotic that inhibits bacterial cell-wall synthesis and acts against susceptible bacteria. |
| cell wall/sel wɔːl/ | A supportive layer outside the cell membrane in plants, fungi and many microorganisms. |
| mutation/mjuːˈteɪʃn/ | A change in genetic material, such as a DNA sequence or chromosome structure. |
| natural selection/ˈnætʃərəl sɪˈlekʃn/ | The process in which inherited traits that improve survival and reproduction become more common in a population over generations. |
The drugs that fight bacteria
- An antibiotic 抗生素 is a drug that kills bacteria or stops them growing.
- They have saved countless lives — but only against bacteria.
- And bacteria are fighting back, by becoming resistant 抗药.
How penicillin 青霉素 works
- Penicillin stops bacteria from building their cell walls 细胞壁.
- As the bacterium grows, its weak wall cannot hold it.
- So the cell takes in water and bursts.
Penicillin stops bacteria building cell walls, so they burst
Penicillin kills bacteria by:
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Penicillin prevents cell-wall synthesis; the growing cell cannot hold the water it absorbs, so it bursts.
Why antibiotics don't beat viruses
- A virus has no cell wall and no chemical reactions of its own to attack.
- It simply uses the machinery of the host cell.
- So there is no antibiotic target in a virus — antibiotics do not work against viral illnesses like colds.
Why do antibiotics not work against viruses?
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Antibiotics target bacterial structures/processes; a virus has none of these, using the host cell instead.
Antibiotic resistance
- A mutation 突变 can make a bacterium resistant — the antibiotic no longer kills it.
- By natural selection 自然选择, the non-resistant bacteria die, the resistant ones survive and multiply, and resistance spreads.
Slowing resistance: only use antibiotics when needed; always finish the full course; use the correct antibiotic; reduce heavy use in farming.
How resistance evolves
Step through natural selection in fast-forward. The antibiotic kills the rest, so only the resistant bacteria are left to breed.
Antibiotic resistance spreads because:
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Resistant bacteria (from mutation) survive the antibiotic and reproduce, so resistance spreads by natural selection.
Put the evolution of antibiotic resistance in order.
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Variation → the antibiotic selects → survivors breed → a resistant population. This is natural selection.
Antibiotic resistance spreads by natural ______ — resistant bacteria survive and reproduce.
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The antibiotic is the selection pressure; only resistant bacteria survive to pass on their genes.
Which action helps slow antibiotic resistance?
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Finishing the course leaves no survivors; avoiding unnecessary use reduces the selection pressure for resistance.
Antibiotics should be taken to treat a common cold.
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Colds are caused by viruses, which antibiotics cannot kill — using them needlessly only drives resistance.
You've got it
- antibiotics kill bacteria — penicillin stops cell wall building, so the cell bursts
- they do not work on viruses (no cell wall, no target — uses host machinery)
- resistance: a mutation + natural selection → resistant bacteria spread
- slow it: only when needed, finish the course, correct drug, less farm use