AQA GCSE Biology Biology Paper 1 (Higher), 2024: Question 2

💡 Key knowledge

• Genes are found on chromosomes in the nucleus.
• CF mainly affects the lungs, pancreas, and small intestine.
• Digestive enzymes break down large food molecules into small soluble molecules.
• Alveoli need a large surface area, a good blood supply, and thin walls for fast diffusion.
• Less oxygen in the blood means less aerobic respiration and less energy released.

🧠 Exam technique

• For 1-mark recall questions, give the exact biological term.
• For explanation questions, link ideas clearly using words like so, therefore, and because.
• When a question asks for three features, give three separate points, not one long sentence.
• Use the command word: describe = say what the features are; explain = say how/why they cause an effect.

❌ Common errors

• Saying the gene is in the DNA only, without stating nucleus or chromosome.
• Mixing up the organs in the diagram.
• Writing general statements like “food is digested badly” without naming enzymes or products.
• For alveoli, writing about moisture or steep concentration gradient is not needed here.

✅ Correct answer

nucleus

The mark scheme also allows chromosome. “DNA” alone is not enough for full credit here.

💡 Key knowledge

In GCSE Biology, genes are sections of DNA found on chromosomes, which are in the nucleus.

🧠 Exam technique

If a question asks “where in a cell?”, the safest answer is usually nucleus. If you want to add detail, you can say on a chromosome in the nucleus.

✅ Correct answer

A, D and E

These letters show the lungs, pancreas and small intestine.

💡 Key knowledge

• CF mainly affects the lungs because sticky mucus builds up there.
• The pancreas makes digestive enzymes.
• The small intestine is where digestion is completed and nutrients are absorbed.

❌ Common errors

• Choosing letters that point to the wrong organ shapes.
• Not matching the organ names to the diagram carefully.

✅ What a full-mark answer should include

• Less digestive enzyme reaches the small intestine.
• Less lipase means less fat is broken down into fatty acids and glycerol.
• Less amylase / carbohydrase means less starch is broken down into sugars (glucose).
• Less protease means less protein is broken down into amino acids.
• Because food is not digested properly, fewer small soluble molecules are available to be absorbed.
• With less absorption, fewer nutrients are available for growth, repair and energy, so body mass is harder to gain.

💡 Key knowledge

Why digestion is affected

• The pancreas makes several digestive enzymes.
• CF reduces the amount of enzyme reaching the small intestine.
• This means large insoluble food molecules are not broken down as effectively.

What enzymes do

• Amylase / carbohydrase breaks starch into sugars, such as glucose.
• Protease breaks proteins into amino acids.
• Lipase breaks fats into fatty acids and glycerol.

🧠 Exam technique

Top answers usually follow this pattern:

less enzyme → less digestion → fewer soluble molecules absorbed → less material for growth and respiration → difficulty gaining body mass

The mark scheme says Level 3 needs both parts: difficulty digesting food and difficulty gaining body mass.

❌ Common errors

• Only saying “food is not digested” without naming enzymes or products.
• Forgetting to explain body mass in terms of fewer nutrients being absorbed.
• Writing that “less food is eaten” — the problem is digestion and absorption, not appetite.

✅ Correct answers

• Large surface area
• Good / efficient blood supply or large capillary network
• Thin walls or walls are one cell thick

💡 Key knowledge

• A large surface area means more oxygen can diffuse in at once.
• A dense capillary network removes oxygen quickly, helping maintain diffusion.
• Thin walls give a short diffusion distance.

🧠 Exam technique

For this question, you only need to name the features. You do not need to explain them in detail unless asked.

❌ Common errors

• Saying “alveoli are moist” — not credited in this mark scheme.
• Saying “steep concentration gradient” — not credited here.
• Saying “thin cell walls” is acceptable, but do not confuse this with general “thin membranes”.

✅ Correct answer points

• Less aerobic respiration
• Less energy released
• This can cause less muscle contraction, muscle fatigue, or an increase in breathing rate / heart rate

The mark scheme also allows the alternative chain: more anaerobic respiration → lactic acid produced → muscle fatigue.

💡 Key knowledge

• Oxygen is needed for aerobic respiration.
• Respiration releases the energy needed for muscle contraction and other body processes.
• If oxygen is low, the body may rely more on anaerobic respiration, which can lead to lactic acid build-up.

🧠 Exam technique

You need a clear chain of reasoning. A strong answer links oxygen shortage to energy shortage, then to body effects such as tired muscles or faster breathing.

❌ Common errors

• Saying “less energy produced” — the mark scheme prefers less energy released.
• Stopping after “less oxygen enters the blood” without explaining the effect on the body.
• Only mentioning one consequence when the question is worth 3 marks.

🎯 One-line answers to remember

• 02.1: nucleus
• 02.2: A, D and E
• 02.4: large surface area, good blood supply, thin walls
• 02.5: less oxygen → less aerobic respiration → less energy

🧠 How examiners reward marks

• 1-mark questions need the exact term.
• 3- and 6-mark questions reward linked explanations, not just single facts.
• For CF digestion, full marks require both digesting food and gaining body mass.