GCSE · Biology · AQA · Spec 8461

Antibiotics and painkillers

Your fever has gone and your headache has eased — but has whatever made you ill actually gone?

You're the doctor

Will this medicine cure it?

A patient comes in ill. First decide what's causing the disease, then choose a medicine, and follow the route to the end to see what that medicine actually does.

What is causing it? → Which medicine? → Does it kill this kind of bacteria?

5 possible routes.

On A patient has an infectious disease. 2 branches to choose from.

Walk every route, not just the one that works. Only one of them ends in a cure — notice what had to be true for it.

Feeling better vs being cured

What did the ibuprofen actually do?

Jas wakes up with a sore throat, a headache and a fever. Jas takes some ibuprofen, and an hour later feels a lot better.

Which is closest to what you think the ibuprofen has done?

It has killed the germs that were causing the illness.It has cured the illness. Jas feels better, so Jas is better.It has eased the symptoms, but it hasn't killed whatever is causing the illness.It did the same job an antibiotic would have done, just faster.

How sure are you?

I'm sureI think soI'm guessing

It has killed the germs that were causing the illness.

This is a common misconception

That's the tempting one, but no. Ibuprofen is a painkiller, and painkillers don't kill pathogens — not bacteria, not viruses. Whatever is causing Jas's illness has not been killed by it.

It has cured the illness. Jas feels better, so Jas is better.

This is a common misconception

Feeling better and being cured are two different things. The ibuprofen has eased the symptoms — the sore throat, the headache, the fever. It hasn't touched the cause, so the disease itself hasn't been cured.

It has eased the symptoms, but it hasn't killed whatever is causing the illness.

This matches the evidence

Exactly. A painkiller treats the symptoms of a disease, not the disease itself. It's making Jas more comfortable, but it has killed no pathogens, so it hasn't cured anything.

It did the same job an antibiotic would have done, just faster.

This is a common misconception

They're completely different jobs. An antibiotic can cure a bacterial disease by killing the bacteria inside the body — as long as it's one that kills that kind. A painkiller kills no pathogens; it just eases how you feel.

Painkillers such as paracetamol and ibuprofen ease symptoms like a headache, a fever or a sore throat. They kill no pathogens, so they do not cure the disease itself.

Predict, then check

On the tree, no route cured a disease caused by a virus. So why not just make a medicine that does?

Antibiotics kill bacteria inside the body. Why is it so hard to make a drug that does the same job on viruses?

A success story — with a catch

How far do you agree?

The claim

Antibiotics have solved the problem of infectious disease.

Place each piece of evidence to load the balance. Mark the strong ones — they count double.

Antibiotics such as penicillin cure bacterial diseases by killing the infective bacteria inside the body.
Evidence 1: does it support or challenge the claim?SupportsChallenges
Strong evidence
The use of antibiotics has greatly reduced deaths from infectious bacterial diseases.
Evidence 2: does it support or challenge the claim?SupportsChallenges
Strong evidence
Antibiotics cannot kill viruses, so they are no help against a disease caused by a virus.
Evidence 3: does it support or challenge the claim?SupportsChallenges
Strong evidence
Strains of bacteria that are resistant to antibiotics have emerged, and infections caused by them are harder to treat.
Evidence 4: does it support or challenge the claim?SupportsChallenges
Strong evidence
Infections caused by resistant bacteria are more likely to kill.
Evidence 5: does it support or challenge the claim?SupportsChallenges
Strong evidence

Your turn

Write it, then mark it

A doctor sees two patients. Patient A has a disease caused by bacteria. Patient B has a disease caused by a virus. Explain how an antibiotic such as penicillin could cure Patient A, why the doctor has to choose which antibiotic to prescribe, and why an antibiotic will not help Patient B. [3 marks]

Your answer

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The mark scheme

The antibiotic kills the (infective) bacteria causing the disease, inside the body. (1 mark)
Any one antibiotic kills only certain kinds of bacteria, so it must be one that kills the kind causing Patient A's disease. (1 mark)
Antibiotics cannot kill viruses (they act only on bacteria), so an antibiotic cannot cure Patient B. (1 mark)

Model answer

The antibiotic kills the bacteria causing Patient A's disease, inside the body, and that is what cures it. The doctor has to choose carefully because any one antibiotic kills only certain kinds of bacteria, so it must be one that kills the kind infecting Patient A. An antibiotic won't help Patient B, because antibiotics cannot kill viruses — they act only on bacteria.

Three separate ideas earn three separate marks: what the antibiotic kills, why the choice of antibiotic matters, and why a virus is out of its reach.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Antibiotics kill certain bacteria. Painkillers ease symptoms. Neither one kills a virus.

What you need to know

Antibiotics, such as penicillin, help to cure bacterial disease by killing the infective bacteria inside the body.
Any one antibiotic kills only certain kinds of bacteria, so the doctor must prescribe the correct one.
Antibiotics cannot kill viruses, and drugs that kill viruses are difficult to develop without damaging the body's tissues.
Painkillers, such as paracetamol and ibuprofen, treat symptoms but do not kill pathogens, so they do not cure the disease.

The big picture

Antibiotics, such as penicillin, are medicines that help to cure bacterial diseases by killing the infective bacteria inside the body — but any one antibiotic kills only certain kinds of bacteria, so the doctor has to prescribe the right one. Antibiotics cannot kill viruses, and drugs that kill viruses are difficult to develop without also damaging the body's tissues. Painkillers such as paracetamol and ibuprofen ease symptoms like a headache, a fever or a sore throat, but they kill no pathogens, so they do not cure the disease itself. Antibiotics have greatly reduced deaths from infectious bacterial diseases, but the emergence of resistant strains is of great concern.

Key points

1To cure a bacterial disease, an antibiotic has to kill the bacteria causing it — so it must be one that kills that kind.

2Antibiotics act only on bacteria. Against a virus, they do nothing.

3Painkillers ease symptoms such as a headache, a fever or a sore throat — the pathogen is not killed.

4Antibiotics have greatly reduced deaths from infectious bacterial diseases.

5However, resistant strains are of great concern: their infections are harder to treat and more likely to kill.

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Worked example

Problem

A patient has a disease caused by bacteria. It is giving them a painful sore throat and a fever. The doctor prescribes an antibiotic that kills this kind of bacteria, and also suggests taking ibuprofen. What does each medicine do, and which one cures the disease?

⚠ Watch out

Thinking an antibiotic will help with any illness. Antibiotics kill only bacteria — and any one antibiotic only certain kinds — so they do nothing against a virus.

🧠

Memory hook

Painkillers kill pain, not pathogens. Each antibiotic kills only certain kinds of bacteria — and no antibiotic kills a virus.

✓

Check yourself

Without looking back: what two things must be true before an antibiotic can cure a patient's disease?

Flashcards

(11)

What is an antibiotic?

A medicine that helps to cure bacterial disease by killing the infective bacteria inside the body.

Penicillin is an example of which kind of medicine?

An antibiotic.

Why can't one antibiotic be used for every bacterial disease?

Any one antibiotic kills only certain kinds of bacteria, so specific bacteria must be treated with specific antibiotics.

Who decides which antibiotic a patient needs, and what must they get right?

The doctor — they must prescribe an antibiotic that kills the kind of bacteria causing the disease.

What effect has the use of antibiotics had on deaths from infectious bacterial diseases?

It has greatly reduced them.

Why is the emergence of antibiotic-resistant strains of bacteria of great concern?

Infections caused by resistant bacteria are harder to treat and more likely to kill.

Can antibiotics kill viruses?

No. Antibiotics act only on bacteria; they cannot kill viral pathogens.

Why is it difficult to develop drugs that kill viruses?

It is hard to kill viruses without also damaging the body's tissues.

What are painkillers used for?

To treat the symptoms of a disease — easing things like a headache, a fever or a sore throat.

Paracetamol and ibuprofen are examples of which kind of medicine?

Painkillers — they ease symptoms but kill no pathogens.

Why doesn't a painkiller cure a disease?

It doesn't kill the pathogen causing the disease — it only eases the symptoms.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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Will this medicine cure it?

What did the ibuprofen actually do?

How far do you agree?

Write it, then mark it

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