Antibiotics, painkillers and drug development – GCSE Biology exam questions with mark scheme

1Grade 4–54 marks

(a) A patient has influenza (flu). Explain why a doctor will not prescribe antibiotics. [2]

(b) Doctors are asked not to prescribe antibiotics for mild bacterial infections. Suggest why. [1]

(a) flu is caused by a virus(1)
(a) antibiotics only kill bacteria / do not kill viruses; accept viruses live inside cells so are hard to kill without damaging cells(1)
(b) to reduce / slow the development (or spread) of antibiotic-resistant strains of bacteria; reject the person / body becoming resistant; ignore 'the body can fight it off' alone(1)
(c) they only treat the symptoms / do not kill the pathogen(1)
Answer: (a) flu is viral; antibiotics don't kill viruses (b) to slow the spread of antibiotic resistance (c) only relieve symptoms
Examiner tip: Say the BACTERIA become resistant, not the person or the body.

2Grade 1–3Foundation5 marks

Many early drugs were first extracted from living organisms.

(a) Complete the table. [3]

Drug	Organism the drug was first extracted from
digitalis	(i) ____________
(ii) ____________	willow tree
penicillin	(iii) ____________

(b) Give the name of the scientist who discovered penicillin. [1]

Where do most new drugs come from today? [1]

(a)(i) foxglove(s) (allow foxglove plant; ignore 'plant' alone)(1)
(a)(ii) aspirin (allow salicylic acid; ignore painkiller)(1)
(a)(iii) Penicillium (mould) (allow mould / fungus; ignore spelling if recognisable; do not accept bacteria)(1)
(b) (Alexander) Fleming (allow phonetic spelling)(1)
(c) made / synthesised by chemists (allow made in a laboratory by the pharmaceutical industry; allow chemically synthesised; ignore 'from scientists' unqualified)(1)
Answer: (a) (i) foxglove (ii) aspirin (iii) Penicillium mould; (b) Alexander Fleming; (c) synthesised by chemists in the pharmaceutical industry.
Examiner tip: Penicillin comes from a mould (a fungus), not from bacteria – writing 'bacteria' for (a)(iii) is the commonest lost mark.

3Grade 1–3Foundation5 marks

A new drug must be tested before doctors can prescribe it.

(a) Draw one line from each word to its meaning. [3]

Word	Meaning
dose	whether the drug is harmful
efficacy	how quickly the drug is sold
toxicity	the amount of the drug that should be given
	how well the drug works
	where the drug was discovered

(b) The stages of testing a new drug are given in the box. They are not in the correct order.

P tested on patients who have the illness

Q tested on cells and tissues in the laboratory

R tested on healthy volunteers

S tested on live animals

Write the letters P, Q, R and S in the correct order. [2]

(a) dose → the amount of the drug that should be given(1)
(a) efficacy → how well the drug works(1)
(a) toxicity → whether the drug is harmful (more than one line from a word cancels the mark for that word)(1)
(b) Q and S (preclinical) are the first two letters, before R and P (clinical) (allow S, Q, R, P or Q, S, P, R for this mark only)(1)
(b) all four in the correct order: Q, S, R, P(1)
Answer: (a) dose – amount to give; efficacy – how well it works; toxicity – whether it is harmful. (b) Q, S, R, P.
Examiner tip: Learn the order as 'lab → animals → healthy people → patients': each stage only happens if the drug was safe in the stage before.

4Grade 4–55 marks

The graph shows the number of deaths from bacterial infections in one country between 1930 and 1970.

(a) Give the number of deaths per 100 000 people in 1940. [1]

(b) Calculate the percentage decrease in deaths per 100 000 people between 1940 and 1960.

Give your answer to 3 significant figures. [2]

(d) Doctors are worried that the number of deaths from bacterial infections could start to rise again in the future.

Suggest why. [1]

(a) 140(1)
(b) (140 − 30) ÷ 140 × 100 (allow 110 ÷ 140 × 100)(1)
(b) 78.6 (%) (allow 78.57…; correct answer with no working = 2 marks; 79 scores 1 mark only as not 3 s.f.)(1)
(c) penicillin / antibiotics (were used to) kill bacteria (inside the body) (idea of killing bacteria needed: ignore 'penicillin was used' / 'penicillin cures disease' unqualified; do not accept antibiotics kill viruses)(1)
(d) (more) bacteria / strains are becoming resistant to antibiotics (so antibiotics no longer kill them) (allow named example e.g. MRSA; ignore 'immune to antibiotics' unless linked to bacteria)(1)
Answer: (a) 140; (b) 78.6%; (c) penicillin/antibiotics were used, which kill bacteria inside the body; (d) antibiotic-resistant strains of bacteria are increasing.
Examiner tip: In (b) divide the decrease by the ORIGINAL (1940) value, not by the 1960 value.

5Grade 4–54 marks

Amira has a sore throat caused by bacteria. Her doctor prescribes two drugs:

penicillin, an antibiotic
paracetamol, a painkiller.

(a) Explain why the doctor prescribes both drugs. [2]

(b) After two days Amira feels better. The doctor tells her to keep taking the penicillin until she has finished the whole course.

Give one reason why. [1]

(c) A few weeks later Amira gets a different bacterial infection. The doctor prescribes a different antibiotic, not penicillin.

Suggest why. [1]

(a) penicillin kills the bacteria (causing the infection) (allow cures the infection / kills the pathogen; do not accept kills the virus)(1)
(a) paracetamol relieves the pain / treats the symptoms (allow because penicillin does not relieve pain / paracetamol does not kill bacteria)(1)
(b) so that all the bacteria are killed / no bacteria survive (allow so that no bacteria survive to mutate / to form resistant strains; allow so the infection does not come back) (ignore 'so the drug works' unqualified)(1)
(c) specific bacteria need to be treated by specific antibiotics / penicillin may not kill this type of bacteria (allow this strain may be resistant to penicillin)(1)
Answer: (a) Penicillin kills the bacteria; paracetamol only relieves the pain/symptoms. (b) To kill all the bacteria, so none survive to mutate into resistant strains. (c) Different bacteria need specific antibiotics / the bacteria may be resistant to penicillin.
Examiner tip: Painkillers never 'kill' anything – say they treat symptoms only, or you lose the mark.

6Grade 6–73 marks

Doctors can use antibiotics to kill bacteria inside the body without damaging the body's own cells.

Very few drugs are available that kill viruses.

Explain why it is difficult to develop drugs that kill viruses without damaging body tissues. [3]

viruses live / reproduce inside (the body's own) cells (allow viruses are not cells / are inside host cells)(1)
so the drug must get into / act inside the body's cells (to reach the virus)(1)
so the drug is likely to damage / kill the body's cells (as well as the virus) (allow drug may stop the cell working / affect normal cell processes; ignore 'side effects' unqualified)(1)
Answer: Viruses live and reproduce inside body cells, so a drug would have to act inside those cells and is likely to damage or kill them too.
Examiner tip: The key idea is WHERE the virus is – inside our own cells – so start with that, then link it to the drug damaging those cells.

7Grade 6–7Higher7 marks

A hospital tested samples of the bacterium Staphylococcus aureus taken from patients. The table shows the percentage of samples that were resistant to antibiotic Z.

Year	Percentage of samples resistant to antibiotic Z
2014	4
2016	7
2018	12
2020	18
2022	27

(a) Calculate the mean increase in the percentage of resistant samples per year between 2014 and 2022. [2]

(b) Describe the trend in the data. [2]

(c) In 2022 a patient at this hospital has an infection caused by S. aureus. Before prescribing an antibiotic, the doctor sends a sample of the bacteria to a laboratory.

Suggest why. Use information from the table. [2]

(d) Scientists are trying to develop new antibiotics.

Suggest one reason why new antibiotics are unlikely to solve the problem of resistance. [1]

(a) (27 − 4) ÷ 8 (allow 23 ÷ 8)(1)
(a) 2.9 (percentage points per year) (allow 2.875 / 2.88; correct answer with no working = 2 marks)(1)
(b) the percentage of resistant samples increases (every time / over time)(1)
(b) the rate of increase gets faster / it increases by more each two years (allow figures, e.g. rises by 3 between 2014 and 2016 but by 9 between 2020 and 2022)(1)
(c) over a quarter / 27% of samples were resistant to Z (in 2022) so Z might not work / the patient's bacteria might be resistant to Z(1)
(c) to find an antibiotic that does kill these bacteria (allow to check which antibiotic the bacteria are sensitive to / specific bacteria need specific antibiotics)(1)
(d) bacteria may also become resistant to the new antibiotics / development of new antibiotics is slow / costly so cannot keep up with new resistant strains(1)
Answer: (a) 2.9 % per year; (b) increasing at an increasing rate; (c) 27% of samples resistant, so test to find an antibiotic that will kill this strain; (d) bacteria can become resistant to new antibiotics too / development is slow and expensive.
Examiner tip: 'Describe the trend' at Higher needs more than 'it goes up' – say how the rate changes.

8Grade 6–77 marks

A company has developed a new drug to treat migraine headaches. The drug has already passed preclinical testing and has been tested on healthy volunteers.

In a double-blind trial, 200 patients with migraines were split into two groups:

group 1 was given the new drug
group 2 was given a placebo.

The table shows the results.

Group	Number of patients	Number of patients whose headache stopped within 2 hours
1 (new drug)	104	65
2 (placebo)	96	27

(a) What is a placebo? [1]

(b) Explain why the trial was double-blind. [2]

(d) Suggest why some patients in group 2 found that their headache stopped. [1]

(e) The results were peer reviewed before they were published. Suggest why. [1]

(a) a substance / tablet that looks like the drug but contains no drug / has no (medical) effect (allow 'sugar pill' / dummy drug; do not accept 'a different drug')(1)
(b) neither the patients nor the doctors / scientists know who has the drug or the placebo(1)
(b) so the results are not biased / affected by (patients' or doctors') expectations (allow so results are valid / fair)(1)
(c) group 1: 62.5 (%) (allow 62 or 63)(1)
(c) group 2: 28.1 (%) (allow 28)(1)
(d) migraines may stop naturally without treatment / placebo effect – patients believe they are being treated so feel better (ignore 'the placebo worked' unqualified)(1)
(e) other scientists / experts check the method / results / conclusions are valid / not biased / to prevent false claims (ignore 'to check it is correct' unqualified)(1)
Answer: (a) A dummy with no drug in it; (b) neither patients nor doctors know who gets the drug, so results are not biased; (c) group 1 62.5%, group 2 28.1%; (d) placebo effect / migraines stop on their own; (e) other scientists check the work is valid.
Examiner tip: The groups are different sizes, so you must compare percentages, not the raw numbers 65 and 27.

9Grade 8–9Higher6 marks

A chemist has synthesised a new chemical, X, that might kill the bacteria that cause a lung infection.

Chemical X must be tested before doctors can prescribe it to patients.

Describe how chemical X would be tested and explain the reason for each stage. [6]

Preclinical: tested on (lung / human) cells and tissues in the laboratory(1)
Preclinical: to find out if X is toxic / kills cells, and whether it kills the bacteria (efficacy), before risking a living organism(1)
Preclinical: then tested on live animals – to check effects / toxicity in a whole body with many organs and systems(1)
Clinical trial: (if safe) tested on healthy volunteers first – to check for side effects / toxicity in humans(1)
Very low dose at first (increased gradually) – so that any harmful effects are small / to find the safe dose(1)
Then tested on patients with the lung infection – to find the efficacy and the optimum dose(1)
Use a placebo / compare with existing antibiotic for a control group – to see whether improvement is due to X(1)
Double-blind – neither patients nor doctors know who has X, so results are not biased(1)
Large number of patients / repeat trials – so results are repeatable / reliable(1)
Results peer reviewed (before publication) – other scientists check the findings are valid, to prevent false claims(1)

Level	Marks	What it looks like
Level 3	5–6	Describes the stages in the correct order from laboratory testing to patients, with a clear reason given for most stages (e.g. toxicity, safety in humans, efficacy, optimum dose). Includes how bias is avoided (placebo / double-blind) or peer review. Uses scientific terms correctly.
Level 2	3–4	Describes several stages in a mostly correct order with some reasons, OR gives a full sequence of stages with few reasons.
Level 1	1–2	Gives one or two relevant stages or ideas (e.g. 'tested on animals', 'tested on people') with little or no reasoning; order may be unclear.
No marks	0	No relevant content.

Answer: Cells/tissues → live animals (preclinical, for toxicity and efficacy) → healthy volunteers at very low dose (safety/side effects) → patients (efficacy, optimum dose) using placebo control and double-blind design → peer review.
Examiner tip: Level 3 needs the stages in the correct sequence AND a reason for each – a list of stages with no 'so that…' stays in Level 2.

10Grade 8–9HigherTriple only7 marks

A patient has an infected wound. A sample of the bacteria from the wound was spread on an agar plate. Paper discs soaked in four different antibiotics, A, B, C and D, were placed on the plate. Each disc had the same concentration of antibiotic.

The plate was incubated for 48 hours. The diagram shows the plate. The table shows the diameter of the clear zone around each disc.

Antibiotic	A	B	C	D
Diameter of clear zone in mm	18	6	24	14

(a) Calculate the area of the clear zone around disc C.

Use the equation: area $= \pi r^2$

Give your answer to the nearest whole number. [2]

(b) Calculate how many times larger the area of the clear zone around disc C is than the area of the clear zone around disc A.

Give your answer to 3 significant figures. [2]

(d) The paper discs have a diameter of 6 mm.

Explain what the result for antibiotic B shows. [2]

(a) r = 12 (mm) and π × 12² seen (allow π × 144)(1)
(a) 452 (mm²) (allow 452.2 from π = 3.14; correct answer with no working = 2 marks; do not credit 1810, which uses the diameter as the radius)(1)
(b) area A = π × 9² = 254(.5) (mm²) seen OR (12 ÷ 9)² seen OR 452 ÷ 254 seen (allow ecf from (a))(1)
(b) 1.78 (allow ecf from (a) correctly rounded to 3 s.f.; correct answer with no working = 2 marks)(1)
(c) C and it has the largest clear zone, so it kills the most bacteria / is most effective against these bacteria (no mark for C alone)(1)
(d) no clear zone / no bacteria killed around B (the clear diameter is the same as the disc) (allow bacteria grow right up to the disc)(1)
(d) so the bacteria are resistant to B / B would not treat this infection (allow B does not work on this type of bacteria)(1)
Answer: (a) 452 mm²; (b) 1.78 times; (c) C – largest clear zone so most effective at killing these bacteria; (d) there is no clear zone, so the bacteria are resistant to B / B will not treat the infection.
Examiner tip: Halve the diameter before using πr² – using the diameter as the radius gives an area four times too big.

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