AQA GCSE Biology Biology Paper 1 (Foundation), June 2024: Question 8

✅ Correct Answer

Nucleus (or chromosome)

❌ Common Errors & Examiner Traps

• Do NOT write "in the DNA": The mark scheme specifically states "ignore in the DNA". DNA is the substance the gene is made from, not the cellular structure/organelle where it is found.
• Writing "cytoplasm" or "mitochondria" (while mitochondrial DNA exists, human nuclear genes like CFTR are in the nucleus).

✅ Correct Answer

A, D and E

💡 Anatomical Map of Figure 7

• A: Lungs (respiratory tract)
• B: Stomach
• C: Large intestine (colon)
• D: Small intestine (ileum/duodenum)
• E: Pancreas (tucked below/behind the stomach)
• F: Liver

🧠 Exam Technique

The question specifically lists: the lungs (A), the pancreas (E), and the small intestine (D). Carefully distinguish between C (the outer loop = large intestine) and D (the inner central coils = small intestine).

✅ Model 6-Mark Answer Structure

The thick mucus in CF blocks pancreatic ducts, reducing enzyme delivery to the small intestine:

• Less protease reaches the gut, so less protein is broken down into amino acids.
• Less lipase reaches the gut, so less lipids/fats are broken down into fatty acids and glycerol.
• Less carbohydrase / amylase reaches the gut, so less starch/carbohydrate is broken down into glucose.

• Fewer small, soluble molecules are available to be absorbed into the bloodstream.
• Fewer amino acids are available for protein synthesis to build new cells, muscle, and tissues.
• Less glucose is absorbed, leading to reduced respiration and thus less energy released for growth and metabolic reactions.
• Fewer fatty acids/glycerol means less fat is stored in adipose tissue.

🧠 Examiner Level Descriptors (How to get 6/6)

• Level 3 (5–6 marks): Clear, detailed points given for both difficulty digesting food and difficulty gaining body mass, logically linked together.
• Level 2 (3–4 marks): Mentions both parts but lacks full logical linking (e.g. names enzymes but fails to connect products to absorption or growth).
• Level 1 (1–2 marks): Isolated simple statements without clear chemical or physiological cause-and-effect.

❌ Common Errors on this 6-Marker

• Only addressing one half: Writing pages about digestion but completely forgetting to explain why they fail to gain body mass caps you at Level 2 (max 4 marks).
• Mismatched enzymes and products: Stating that protease breaks down fat, or lipase produces amino acids. Always pair them correctly!
• Saying "energy is produced / made": Respiration does not make or create energy; it releases energy.

💡 Summary Table: Enzyme, Substrate & Product

• Protease : Proteins → Amino acids (needed for growth & muscle repair)
• Lipase : Lipids/Fats → Fatty acids + Glycerol (needed for fat storage & cell membranes)
• Amylase/Carbohydrase : Starch → Glucose (needed for respiration to release energy)

✅ Correct Answer (Pick any 3)

• Large surface area (or large surface area to volume ratio).
• Thin walls / walls are one cell thick (provides a short diffusion distance).
• Rich / efficient blood supply (or large capillary network / many capillaries to maintain a steep concentration gradient).

❌ Severe Examiner Traps

• "Thin cell walls": ⚠️ DO NOT SAY THIS! Animal cells do not have cell walls. You must say the alveolar wall is one cell thick or thin walls.
• "Alveoli are thin": Too vague. The walls are thin, not the entire alveolar sac.
• "Thin cell membrane": Ignored by examiners; cell membranes have a fixed thickness.
• "Moist surface" / "Steep concentration gradient": The mark scheme specifically states ignore references to alveoli being moist and ignore steep concentration gradient (as a feature itself, rather than the blood supply causing it).

✅ Model Answer: Two Valid Routes

• Less aerobic respiration occurs in cells [1 mark].
• So less energy is released [1 mark].
• Leading to less muscle contraction, extreme tiredness/fatigue, or increased breathing rate/heart rate to compensate [1 mark].

• Body switches to more anaerobic respiration [1 mark].
• Lactic acid is produced and builds up [1 mark].
• Causing muscle fatigue / cramping / pain [1 mark].

❌ Critical Language Error

Never say: "less energy is made / created / produced".

Under the First Law of Thermodynamics, energy cannot be created or destroyed. In GCSE Biology, you must strictly state that less energy is released from glucose.

🧠 Exam Technique: Chain of Cause and Effect

For a 3-mark "explain" question, always write a 3-step causal chain:

Reduced O₂ intake → Cellular process affected (respiration) → Physiological symptom (fatigue / muscle weakness)

Writing only symptoms (e.g. "they get tired and breathe faster") without mentioning cellular respiration will cost you 2 out of the 3 marks!