AQA GCSE Combined Science: Trilogy Biology Paper 2 (Higher), 2019: Question 6

✅ Correct answer

Homeostasis is the regulation/control of the internal conditions of the body to keep them stable.

For full marks, you can also mention that this is to keep conditions optimum for enzyme activity.

💡 Key knowledge

• Homeostasis means keeping the internal environment constant.
• Examples include blood glucose, temperature, and water balance.
• AQA often rewards the idea of internal conditions staying the same or being kept at optimum levels.

🧠 Exam technique

• If the question says “define”, give a short, accurate statement.
• Use the word internal and either control or regulation.
• Adding “for optimum cell/enzyme function” can secure the second mark.

❌ Common errors

• Just saying “keeping the body healthy” is too vague.
• Describing a process, but not defining the term.
• Forgetting that homeostasis is about internal conditions.

✅ Correct answer

Glucagon

💡 Key knowledge

• Glucagon is released by the pancreas when blood glucose is too low.
• It causes the liver to release glucose into the blood.
• This helps blood glucose rise back to normal.

🧠 Exam technique

This is a recall mark: spelling must be correct enough to be unambiguous.

❌ Common errors

• Insulin is wrong here — insulin lowers blood glucose.
• “Adrenaline” is not the expected answer for this question.

✅ Correct answer

Person B’s blood glucose is already above the normal fasting range before the glucose drink.

After the drink, it rises to a very high level of about 13.2 mmol/dm³.

It does not return to the normal range after 3 hours and is still about 12.0 mmol/dm³.

💡 Key knowledge

• Normal fasting blood glucose: 3.5–5.5 mmol/dm³
• Normal non-fasting blood glucose: 4.0–7.8 mmol/dm³
• Diabetes is suggested when blood glucose stays above the normal range.

🧠 Exam technique

• Use data from the graph for full credit.
• Compare person B’s values with the normal range.
• You only needed any two strong points for the marks, but adding a third makes the answer secure.

❌ Common errors

• Only saying “the line goes up” — that is not enough.
• Referring to person A when the question is about person B.
• Not stating that the values are outside the normal range.

✅ Correct answers

Person A: Type 2 diabetes

Reason: the pancreas is producing lots of insulin, but body cells cannot respond properly to it, so glucose stays too high.

Person B: Type 1 diabetes

Reason: the pancreas is not producing enough insulin to control blood glucose.

💡 Key knowledge

• Type 1 = little or no insulin produced.
• Type 2 = insulin is produced but body cells become resistant / do not respond properly.
• The insulin table supports the diagnosis:
  • Person A = 280 units, above normal range 50–175
  • Person B = 20 units, below normal range 50–175

🧠 Exam technique

• You needed the type of diabetes and a reason for each person.
• Make sure the reason matches the type.
• Use the table data as evidence — that is what gets you the mark.

❌ Common errors

• Mixing up Type 1 and Type 2.
• Saying “resistant to insulin” for Type 1 — that is wrong.
• Just writing “high insulin” or “low insulin” without linking it to the type.

✅ Correct answer

A strong answer should include these linked points:

• Starving children have used up their glycogen stores in the liver and muscles.
• They need the liver enzyme to release glucose from fats.
• The lychees contain a molecule that stops this enzyme working.
• So the children cannot release enough glucose.
• Blood glucose falls too low, causing hypoglycaemia.
• There is not enough glucose for cell respiration, so they may die.

💡 Key knowledge

• Glycogen is the stored form of carbohydrate in liver and muscle.
• When blood glucose is low, glucagon causes the liver to release glucose.
• If the enzyme is blocked, glucose cannot be made/released quickly enough.
• Cells need glucose for respiration to release energy.
• Children who have eaten during the day are less affected because they still have glycogen stores.

🧠 Exam technique

• For 6 marks, write a logical sequence of cause and effect.
• Use words like because, so, and therefore.
• Include the idea of low glucose leading to insufficient respiration.
• Explain the difference between starving children and children who have eaten: the latter still have fuel stores available.

❌ Common errors

• Only saying “they get poisoned” without explaining the biology.
• Forgetting glycogen stores.
• Not linking blocked enzyme action to low blood glucose.
• Stopping at “they get low glucose” without explaining why that is dangerous.

💡 Key facts to memorise

• Homeostasis = maintaining internal conditions.
• Low blood glucose → glucagon.
• Type 1 = not enough insulin.
• Type 2 = insulin resistance.
• Hypoglycaemia = dangerously low blood glucose.

🧠 How to score well

• Use correct scientific terms.
• Quote data from graphs and tables.
• Compare to the normal range.
• For explanations, build a cause-and-effect chain.

❌ Biggest traps

• Insulin vs glucagon confusion.
• Mixing up Type 1 and Type 2 diabetes.
• Not using graph numbers.
• Writing isolated statements instead of a linked explanation.