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

✅ Correct answers

Each correct line = 1 mark.

💡 Key knowledge

• Gonorrhoea is a bacterial sexually transmitted infection.
• Measles is caused by a virus.
• Not all pathogen types on the page will be used.

🧠 Exam technique

• Only draw one clear line from each disease.
• The mark scheme says extra lines negate the mark.
• If you are unsure, eliminate the obviously wrong options first.

❌ Common errors

• Adding extra lines “just in case”. This can lose the mark.
• Confusing measles with a bacterial disease.
• Thinking gonorrhoea is caused by a virus because it is an STI.

✅ Correct answers

Any two from:

• Skin acts as a barrier.
• Mucus in the trachea / bronchi / airways / nose traps pathogens.
• Cilia in the trachea / bronchi / respiratory tract move mucus away.
• Hydrochloric acid in the stomach kills pathogens.
• Tears.
• Scab forms if you cut yourself.

💡 Key knowledge

• Skin is a physical barrier.
• Mucus traps pathogens.
• Cilia move mucus out of the airways.
• Stomach acid kills many pathogens swallowed in food or mucus.

🧠 Exam technique

• Give exactly two distinct ways.
• Make sure they are about preventing entry, not the immune response after infection.
• Short, clear statements are enough for 2 marks.

❌ Common errors

• Talking about antibodies or white blood cells. The mark scheme says to ignore immune response here.
• Saying just “hairs” instead of cilia.
• Writing “mucus” with no context can be risky unless clearly linked to nose/airways.

✅ What gets the marks

• Reference to white blood cells.
• Phagocytes engulf/digest pathogens.
• Antibodies are produced.
• Antibodies destroy pathogens / attach to pathogens / make them clump together.
• Antitoxins are produced to neutralise toxins.
• Memory cells give a faster response next time.

💡 Key knowledge

• Pathogens have antigens on their surface.
• Antibodies are specific to particular antigens.
• Phagocytosis means engulfing and digesting pathogens.
• Antitoxins work against toxins made by pathogens, especially bacteria.
• Memory cells are why the second response is faster.

🧠 Exam technique

• This is a level-of-response question, so linked explanation matters.
• To reach the top level, do more than list facts: explain what each white blood cell action does.
• A strong structure is:
  1. State white blood cells defend the body.
  2. Explain phagocytes.
  3. Explain antibodies.
  4. Explain antitoxins.
  5. Explain memory cells.
• Use biological words accurately: engulf, digest, antibodies, antitoxins, memory cells.

❌ Common errors

• Only saying “white blood cells kill pathogens” with no detail. That is too vague for top marks.
• Mixing up antibodies and antitoxins.
• Forgetting to mention phagocytes or memory cells.
• Describing vaccination instead of the immune response itself.

✅ Correct answer

Any one of these:

• HIV is a virus.
• Antibiotics do not kill viruses.
• Antibiotics are used to kill bacteria, not viruses.

💡 Key knowledge

• Antibiotics work against bacteria.
• HIV is a virus.

❌ Common errors

• Saying “antibiotics are too weak”.
• Saying “HIV is not a bacterium” without linking to antibiotics can be less clear, though the mark scheme does allow it if the point is clear.

✅ Correct answers

Any two from:

• Avoid sexual intercourse.
• Use a condom.
• Do not share needles.
• Use antiretroviral drugs.
• Screen blood used for transfusions.
• Have regular HIV checks/tests. (Allowed by examiner notes.)
• Do not exchange body fluids. (Can gain 1 mark if nothing else scores.)

🧠 Exam technique

• Give two clearly different methods.
• Best exam-safe pair: use a condom and do not share needles.
• Be specific: “use protection” is too vague unless clearly meaning safe sex.

❌ Common errors

• Handwashing is not credited here.
• Social distancing is not credited here.
• “Use contraception” is too vague because not all contraception prevents HIV spread.
• “Use medication” is too vague unless you say antiretroviral drugs.

💡 Key knowledge

• HIV can spread through sexual contact, shared needles and infected blood.
• Prevention focuses on reducing contact with infected body fluids.

✅ Correct answer

HIV damages the immune system.

💡 Key knowledge

• If the immune system is damaged, the body cannot defend itself well against other pathogens.
• This means infections that are normally less serious can become dangerous.

❌ Common errors

• Choosing “Pathogens enter the body more easily”. That is not the key reason in the mark scheme.
• Choosing “People with AIDS are immune to HIV”. This is incorrect.

💡 Must-know facts

• Gonorrhoea → bacterium
• Measles → virus
• Skin, mucus, cilia, stomach acid help stop entry of pathogens
• White blood cells: phagocytes, antibodies, antitoxins, memory cells
• Antibiotics do not work on viruses like HIV
• Prevent HIV spread with condoms, not sharing needles, screened blood, antiretroviral drugs
• HIV damages the immune system

🧠 How to maximise marks

• Be precise with pathogen names and immune system terms.
• For short questions, give exactly the number of answers asked for.
• For the 6-marker, explain several processes in sequence.
• Avoid vague phrases like “fights disease” unless you add how.
• Use biology vocabulary accurately to show secure knowledge.