AQA GCSE Combined Science: Trilogy Biology Paper 1 (Higher), 2020: Question 4

12 marks · Standard Demand difficulty · Short Answer

Answer questions on differences between bacterial and plant cells, how vaccines prevent gonorrhoea, and how salmonella infection is reduced and controlled.

Practise this question

Question

The question page contains five Biology short-answer parts labelled 04.1 to 04.5, total 12 marks, with ruled lines for written responses. Part 04.1 asks for four differences between a bacterial cell and a plant cell for 4 marks. Part 04.2 states that gonorrhoea is a bacterial disease and asks how a new vaccine would work to prevent gonorrhoea for 4 marks; part 04.3 explains that UK chickens are vaccinated against Salmonella and asks how this reduces salmonella food poisoning in humans for 2 marks. Part 04.4 asks for one non-vaccination method to control spread of salmonella food poisoning from one human to another for 1 mark, and part 04.5 asks why cases are usually higher in summer than winter for 1 mark.
Question text

04 Cells are the basic units of all forms of life.

04.1 Describe four differences between a bacterial cell and a plant cell.

[4 marks]

04.2 Gonorrhoea is a bacterial disease.

A new vaccine is being developed against gonorrhoea.

Describe how a vaccine would work to prevent gonorrhoea.

[4 marks]

Another disease caused by bacteria is salmonella food poisoning.

In the UK, chickens are vaccinated against Salmonella bacteria to reduce the number

of cases of food poisoning in humans.

04.3 Explain how vaccinating chickens reduces the number of cases of salmonella

food poisoning.

*16* [2 marks]

04.4 Give one way that the spread of salmonella food poisoning from one human to

another is controlled.

Do not refer to vaccination in your answer.

[1 mark]

04.5 The number of cases of salmonella food poisoning is usually higher in summer than

in winter.

Suggest one reason why.

[1 mark]

Mark scheme

Show the mark scheme The mark scheme is a table listing acceptable answers, extra guidance, marks and specification references for questions 04.1 to 04.5. For 04.1 it credits any four differences such as bacterial cells being smaller, lacking chloroplasts, mitochondria, a nucleus and a large permanent vacuole, having plasmids, a non-cellulose cell wall, smaller ribosomes, and possibly a flagellum or slime capsule. For 04.2 it credits describing vaccination using dead, inactive or weakened pathogens or antigens, antibody production, memory cells and rapid antibody production on re-exposure, preventing a large enough population to cause disease. For 04.3 it credits that vaccinated chickens or eggs contain fewer bacteria so fewer are ingested by humans or fewer toxins are produced; for 04.4 it credits measures such as washing hands before preparing food or after using the toilet; for 04.5 it credits that warmer weather allows bacteria to reproduce faster, with an allowed alternative about improperly cooked barbecue food.

AO /

Question Answers Extra information Mark

Spec. Ref.

04.1 allow converse statements AO1

‘it’ refers to bacteria 4.1.1.1

any four from: 4 4.1.1.2

• bacterial cell is smaller (than

a plant cell)

• bacterial cell does not have ignore chlorophyll

chloroplasts (plant cell does)

• bacterial cell does not have allow bacterial cell does not

its DNA / genetic material have a nucleus (plant cell does)

inside a nucleus (plant cell

does) allow bacterial cell has DNA /

genetic material in a ring / loop

(plant cell does not)

allow bacterial cell has DNA /

genetic material free in

cytoplasm

• bacterial cell (may) have

plasmids (plant cell does not)

• bacterial cell does not have

mitochondria (plant cell does)

• cell wall in bacterial cells is

not made of cellulose (cell

wall in plant cells is)

• bacterial cell does not have a

large / permanent vacuole

(plant cell does)

• bacterial cell has smaller do not accept idea that bacterial

ribosomes (than plant cells) cells do not have ribosomes

allow bacterial cell (may) have a

flagellum (plant cells do not)

allow bacterial cell (may) have a

slime capsule (plant cell does

not)

04.2 any four from: 4 AO1

14 • dead / inactive / allow introduce / inject 4.3.1.7

weakened form of antigen(s) from the pathogen

pathogen / bacterium / AO2

microorganism is allow dead / inactive / weakened 4.3.1.1

introduced / injected form of Gonorrhoea (bacteria)

introduced / injected

do not accept inject Gonorrhoea

disease

• white blood cells do not accept incorrect white

stimulated to produce blood cell, eg phagocyte

antibodies

• reference to memory

cells made or remain

• on re-exposure specific / allow on re-exposure specific /

correct antibodies are correct antibodies are produced

made (very) quickly in large quantities

• bacteria / pathogens / allow bacteria / pathogens /

microorganisms killed microorganisms killed and do

and do not produce a not produce a large enough

large enough population population to produce toxins

to cause the disease

04.3 ignore references to immunity AO2

unqualified 4.3.1.3

4.3.1.1

fewer bacteria / pathogens in allow fewer chickens / eggs will 1

chicken / eggs / food carry the bacteria / pathogens

ignore chickens do not get

disease / infected 1

(so) fewer bacteria are ingested allow idea of fewer bacteria

(by humans) being passed on to humans in

food

or

fewer bacteria / pathogens allow idea of fewer bacteria

ingested (by humans) (1) being passed on to humans in

15 food (1)

(so) fewer toxins produced (1)

04.4 ignore wash hands unqualified AO1

4.3.1.1

wash hands before preparing allow good food hygiene 1 4.3.1.3

food

wash hands after using the toilet allow clean areas where a

person has been ill

allow do not shake hands (with

someone who has food

poisoning)

04.5 warmer weather so bacteria ignore bacteria are killed at low 1 AO3

reproduce / increase faster temperatures 4.3.1.1

4.3.1.3

allow food not cooked properly

on barbeques

Total 12

How to answer it

Gonorrhoea, Salmonella and Cell Differences

AQA GCSE Combined Science: Trilogy 4.1 Cells + 4.3 Infection and response

What this question tests

This question checks whether you can compare cell structures and explain how vaccines and hygiene reduce bacterial disease. It rewards clear recall of key facts, using correct biological terms, and giving short cause-and-effect explanations.

Maximise marks by: naming specific differences, explaining the immune response to vaccination, and linking reduced bacterial spread to fewer cases in humans.

Question 04.1 – Differences between a bacterial cell and a plant cell [4]

Describe four differences between a bacterial cell and a plant cell.

✅ Correct answers

  • A bacterial cell is smaller than a plant cell.
  • A bacterial cell does not have chloroplasts.
  • A bacterial cell does not have a nucleus; its DNA is not inside a nucleus.
  • A bacterial cell may have plasmids, but a plant cell does not.
  • A bacterial cell does not have mitochondria.
  • The bacterial cell wall is not made of cellulose.
  • A bacterial cell does not have a large permanent vacuole.
  • A bacterial cell has smaller ribosomes than a plant cell.

💡 Key knowledge

  • Bacteria are prokaryotes and plant cells are eukaryotes.
  • Prokaryotic cells have DNA free in the cytoplasm or in a loop/ring.
  • Plant cells have a nucleus, cellulose cell wall, chloroplasts, mitochondria, and a large permanent vacuole.
  • The mark scheme allows any four valid differences.

🧠 Exam technique

  • You only need four clear differences for 4 marks.
  • Write them as short, separate statements.
  • Use comparison words: bacterial cell... / plant cell...
  • Best answers are precise, e.g. “bacterial cell does not have a nucleus” rather than just “different nucleus”.

❌ Common errors

  • Saying bacteria do not have ribosomes is wrong — they do, but they are smaller.
  • Writing bacteria have chlorophyll is not a valid difference here.
  • For cell wall, say not cellulose, not just “different wall”.
  • Do not mix up plasmids with the main chromosome DNA.
How marks are awarded: 1 mark for each correct difference. You can score full marks with four accurate, distinct statements.

Question 04.2 – How a vaccine works against gonorrhoea [4]

Describe how a vaccine would work to prevent gonorrhoea.

✅ Correct answer points

  • A dead, inactive, or weakened form of the gonorrhoea bacterium, or its antigens, is injected.
  • White blood cells are stimulated to produce antibodies.
  • Memory cells are made and remain in the body.
  • If the person is exposed again, the body produces specific antibodies quickly and in large quantities.
  • The bacteria are killed before they can reproduce enough to cause disease.

💡 Key knowledge

  • Vaccination does not cure the disease — it helps prevent it.
  • The immune system responds to antigens on the pathogen.
  • Memory cells give a faster secondary response.
  • Top answers mention the pathogen being destroyed before it produces enough toxins or causes symptoms.

🧠 Exam technique

  • Use the sequence: inject antigen → white blood cells respond → antibodies + memory cells → faster future response.
  • Link each stage clearly to prevention.
  • If you mention “immune system”, still explain how it protects the body.

❌ Common errors

  • Do not say “inject gonorrhoea” — the vaccine uses a dead/inactive/weakened form or antigens.
  • Do not write phagocyte instead of white blood cell unless you explain the correct antibody response.
  • Do not confuse antibodies with antigens.
  • Leaving out memory cells often loses a key mark.
How marks are awarded: 4 marks for four relevant points. The best answers explain the full pathway, not just one or two steps.

Question 04.3 – Why vaccinating chickens reduces salmonella cases [2]

Explain how vaccinating chickens reduces the number of cases of salmonella food poisoning.

✅ Correct answer

  • Vaccinated chickens are less likely to carry Salmonella.
  • So there are fewer bacteria/pathogens in chicken, eggs, or food.
  • That means humans ingest fewer bacteria, so fewer cases of food poisoning occur.
  • Another valid point: fewer toxins are produced because fewer bacteria are present.

💡 Key knowledge

  • The mark scheme accepts either:
    fewer bacteria in food → fewer ingested by humans
    or
    fewer bacteria ingested → fewer toxins produced.
  • You do not need to mention immunity in the chicken for this question.

🧠 Exam technique

  • Make a simple cause-and-effect chain.
  • One mark for the reduced bacteria in food/eggs/chickens, one mark for the reduced risk to humans.
  • Keep it short and direct.

❌ Common errors

  • Writing only “vaccination protects humans” is too vague.
  • Talking about antibodies in humans does not answer this question.
  • Missing the link to fewer bacteria in food loses the explanation mark.
How marks are awarded: 1 mark for fewer bacteria in chickens/eggs/food, and 1 mark for fewer bacteria being eaten by humans or fewer toxins being produced.

Question 04.4 – Controlling spread of salmonella [1]

Give one way that the spread of salmonella food poisoning from one human to another is controlled. Do not refer to vaccination.

✅ Correct answers

  • Wash hands before preparing food.
  • Wash hands after using the toilet.
  • Any clear example of good food hygiene.
  • Cleaning areas where an infected person has been may also be accepted.

🧠 Exam technique

  • For 1 mark, one valid hygiene action is enough.
  • Be specific: say when hands are washed.

❌ Common errors

  • Writing just “wash hands” may be too vague unless the context is clear.
  • Do not mention vaccination — the question excludes it.
  • Answers like “take medicine” or “isolate forever” are not the expected hygiene control methods here.

Question 04.5 – Why salmonella is more common in summer [1]

The number of cases of salmonella food poisoning is usually higher in summer than in winter. Suggest one reason why.

✅ Correct answer

  • Warmer weather means bacteria reproduce faster.
  • Acceptable extra idea: food may not be cooked properly on barbecues.

💡 Key knowledge

  • Bacteria grow faster in warm conditions.
  • More rapid bacterial reproduction increases the chance of food poisoning.

❌ Common errors

  • Do not say bacteria are killed by summer heat; the mark scheme wants the opposite idea.
  • Answers about “more people go outside” are too vague unless linked to unsafe food preparation.
How marks are awarded: 1 mark for one clear reason linked to warmer conditions or barbecue cooking.

Examiner summary: what top answers did well

💡 What got full marks

  • Using exact biology terms: nucleus, plasmids, antigens, antibodies, memory cells.
  • Making direct comparisons in 04.1.
  • Giving a clear immune-response sequence in 04.2.
  • Showing the chain of transmission in 04.3.

🧠 Final exam advice

  • If a question says describe, give short factual points.
  • If it says explain, include a cause and effect.
  • For 4-mark questions, aim for 4 separate valid points unless the mark scheme requires linked ideas.

Topics

Biology · B1: Cell Biology · B3: Infection and Response

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Biology Paper 1 (Higher), 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.