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Drugs and antibiotics Cambridge IGCSE Combined Science revision

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In plain words

A drug is anything you take that changes how your body's chemistry works: a painkiller, caffeine, a medicine. Antibiotics are drugs that kill bacteria, and they've saved millions of lives. But bacteria are evolving ways round them, which is why they must be used with care.

Three things to know

  1. A drug is any substance taken into the body that modifies or affects chemical reactions in the body.
  2. Antibiotics treat infections caused by bacteria. They have no effect on viruses, so they are useless against colds and flu.
  3. Some bacteria have become resistant to antibiotics. To slow this down, antibiotics should be used only when needed, and the whole course should be finished.

Tips and tricks

  • Antibiotics kill bacteria, not viruses. This is the most-tested fact in the topic.
  • It's the bacteria that become resistant, not the person.
5 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Drugs and antibiotics: 5 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

  1. What do antibiotics treat?
    • viral infections
    • bacterial infections (the answer)
    • broken bones
    • all diseases

    They kill bacteria or stop them growing.

  2. Why are antibiotics not used to treat a cold?
    • Colds are too mild.
    • Colds are caused by viruses. (the answer)
    • Antibiotics are too expensive.
    • Colds are caused by fungi.

    Antibiotics have no effect on viruses.

  3. What is a drug?
    • only an illegal substance
    • a substance that affects chemical reactions in the body (the answer)
    • a kind of food
    • a vitamin only

    Medicines, caffeine and alcohol are all drugs.

  4. How can the spread of antibiotic resistance be slowed?
    • by taking antibiotics for every illness
    • by using antibiotics only when necessary (the answer)
    • by stopping the course early
    • by sharing antibiotics

    Less use means less chance for resistant bacteria to take over.

  5. What does it mean if bacteria are resistant to an antibiotic?
    • The patient is immune.
    • The antibiotic no longer kills them. (the answer)
    • They are viruses.
    • They are harmless.

    MRSA is an example.

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