AQA GCSE Combined Science: Trilogy Biology Paper 1 (Foundation), June 2025: Question 6

✅ Acceptable Answers (Any 1)

• Touch / direct contact (e.g. touching blisters or contaminated skin/surfaces).
• Airborne droplets (e.g. coughing or sneezing into the air).

❌ Common Errors & Mark Loss

• Stating sexual transmission (mark scheme explicitly says: ignore sexual intercourse ).
• Writing just "by germs" or "by being near them" without identifying the route (droplets or touch).

✅ Acceptable Answers

• Chickenpox is caused by a virus.
• Alternative: Antibiotics only kill/treat bacteria (or chickenpox is not caused by a bacterium).

💡 Key Knowledge

Viruses reproduce inside host body cells. Antibiotics work by disrupting bacterial structures (like cell walls) or bacterial metabolism, neither of which affects viruses. Damaging the virus using chemicals often means damaging the host's own tissues.

❌ Common Error

• Confusing virus resistance with antibiotic resistance. Saying "the virus is immune or resistant to antibiotics" earns 0 marks. Antibiotics simply have no target mechanism in viruses.

✅ Acceptable Answers (Any 1)

• Inactive / dead / weakened pathogen (or named pathogen: virus).
• Antigens (or surface proteins from the pathogen).
• mRNA (from the pathogen).

🧠 Exam Technique

Always pair an adjective like dead, weakened, or inactive with the word pathogen, virus, or microbe. Never write "a small dose of the disease" — a disease is the condition, not the physical substance injected.

✅ The "Big Three" Clinical Trial Targets

1. Toxicity: To check if it is poisonous / harmful / safe / check for side effects.
2. Efficacy: To test whether it actually works (prevents infection / produces antibodies).
3. Dose: To determine how much is needed / the optimum concentration.

🧠 Revision Mnemonic: T-E-D

Whenever AQA asks why new drugs or vaccines are tested in clinical trials, think TED:

• Toxicity (Is it safe?)
• Efficacy (Does it work?)
• Dose (How much should we give?)

❌ Pitfall to Avoid

Do not write vague statements like "to see if it is dangerous" (Mark scheme: ignore to check it is not dangerous ). Use precise terms: toxicity, safety, or side effects.

💡 What Top-Tier (Level 3: 5–6 Marks) Responses Must Contain

The question explicitly gives you two bullet points. To achieve Level 3, you must explain both phases logically:

1. Primary Response (to the vaccine): White blood cells detect antigens and produce specific antibodies + form memory cells.
2. Secondary Response (future infection): Memory cells rapidly produce huge quantities of the specific antibody, destroying the virus before symptoms develop.

🧠 Step-by-Step Model Answer Structure

❌ Key Misconceptions & Traps

• "The vaccine fights the disease": No, the vaccine stimulates the body's own white blood cells to respond.
• Confusing Antibodies and Antigens: Antigens are molecular markers on pathogens; antibodies are Y-shaped proteins made by white blood cells.
• Saying "Antibodies produce white blood cells": It is always the white blood cells that produce the antibodies!
• Missing the comparative language: For the secondary response, you must use comparative words: faster, higher concentration, sooner.

📐 Marking Level Descriptors

• Level 3 (5–6 marks): Both primary response (to vaccine) AND secondary response (re-infection) are clearly explained with correct terminology (antigens, specific antibodies, memory cells).
• Level 2 (3–4 marks): Good points made about either the vaccine or the re-infection, but linking is incomplete or one aspect is weak.
• Level 1 (1–2 marks): Isolated points stated (e.g. "makes antibodies", "fights it faster") without logical flow.