AQA GCSE Combined Science: Trilogy Biology Paper 2 (Higher), June 2025: Question 6

✅ Correct Answer

y = mx + c

💡 Key Knowledge

A linear relationship means that if you plot the variables on a graph, you get a straight line.

• m = gradient of the line
• c = y-intercept (where the line cuts the y-axis)

❌ Common Errors

Confusing linear equations with quadratic equations (such as y = mx² + c ) or Einstein’s mass-energy equation ( E = mc² ).

✅ Model Answer (Level 3, 6 Marks)

How the test indicates the type of diabetes:

• Type 1 diabetes: The pancreas cannot produce enough insulin. Because C-peptide is made alongside natural insulin, a person with Type 1 will have low or no C-peptide in their blood, even if they inject insulin.
• Type 2 diabetes: The pancreas still produces insulin, but target body cells no longer respond to it. Therefore, a person with Type 2 will have normal or high levels of C-peptide.

Importance of getting the diagnosis right:

• If a patient is found to have Type 2 instead of Type 1, they can stop taking unnecessary insulin injections.
• Insulin injections are expensive and carry unpleasant side-effects or risks (e.g. hypoglycaemia).
• Type 2 diabetes can be managed using a carbohydrate-controlled diet, increased exercise, or oral tablets rather than daily injections.

🧠 Exam Technique: Level 3 Marking Criteria

To reach Level 3 (5–6 marks), examiners look for:

• Clear discussion of both Type 1 and Type 2 diabetes.
• Direct link between insulin production in each type and the resulting C-peptide concentration.
• Clear explanation of the practical importance (treatment change, stopping injections, lifestyle management).

❌ Common Errors & Misconceptions

• Mixing up the causes: Stating that Type 1 is caused by diet or that Type 2 produces no insulin.
• Only addressing one bullet point from the prompt (e.g. explaining the test results but failing to state why the diagnosis matters).
• Vaguely writing "they can take medicine" without identifying lifestyle changes (diet/exercise) or avoiding injections.

✅ Correct Answer

Pancreas

💡 Key Knowledge

The pancreas is the dual-function organ responsible for monitoring blood glucose levels and secreting both insulin and glucagon.

❌ Common Trap

Selecting Liver. The liver is the target organ where glucagon acts, but it is not the organ that produces glucagon.

📐 Step-by-Step Explanation (4 Clear Marking Steps)

1. Step 1 (Hormone trigger): When blood glucose falls low, insufficient glucagon is released by the pancreas.
2. Step 2 (Liver conversion): Less glycogen is converted into glucose.
3. Step 3 (Cellular supply): Less glucose is delivered to body cells for respiration.
4. Step 4 (Energy transfer): Less energy is released / transferred for muscle contraction, causing tiredness and weakness.

🧠 Crucial Scientific Vocabulary

• Glucagon = the hormone (chemical messenger).
• Glycogen = the insoluble storage carbohydrate in the liver and muscles.
• Glucose = the soluble sugar needed for respiration.

Memory tip: "Gluca-GONE" makes the glucose return when blood sugar is gone!

❌ The #1 Mark-Losing Error in GCSE Biology

Never write: "Energy is produced" or "energy is made / created".

The conservation of energy means energy cannot be created. The mark scheme explicitly states: