AQA AS Level Biology Paper 1, June 2022: Question 6
7 marks · Medium difficulty · Practical Techniques & Data Analysis
Calculate the ratio of the mass of iron ions in the plasma of a person with haemochromatosis to that of a healthy person using given data and explain iron ion roles and transport mechanisms.
Practise this questionQuestion
Question text
06.1 Explain a property of iron ions that enables these ions to carry out their role in red
blood cells.
[2 marks]
06.2 The hormone hepcidin controls the iron ion concentration in blood plasma. Hepcidin
affects ferroportin, the iron ion channel protein in cell-surface membranes.
Figure 7 shows how hepcidin controls the iron ion concentration in plasma.
Figure 7
People with the disease haemochromatosis do not produce hepcidin.
Use information in Figure 7 to explain why the iron ion concentration is higher in the
plasma of people with haemochromatosis.
[3 marks]
06.3 The mass of iron ions in the plasma of a person with haemochromatosis is 6104 μg
The iron ion concentration in the plasma of a healthy person is 50 μg dm–3
The volume of blood in each of these people is 4000 cm3
Calculate the ratio of the mass of iron ions in the plasma of the person with
haemochromatosis to the mass of iron ions in the plasma of the healthy person.
[2 marks]
Answer
Mark scheme
Show the mark scheme
Question Marking Guidance Mark Comments
2+
06.1 1. (Is) charged/polar 1. Accept Fe OR
3+
Fe for ‘charged’
OR
(Is) part of haem(oglobin);
2. (So) binds/associates/loads (with) oxygen
OR (2 x AO1)
(So) forms oxyhaemoglobin
OR
2. Accept ‘carries’ for
(So) transports oxygen; transports
06.2 1. Less/no ferroportin hydrolysis/breakdown; 1. and 2. Accept
‘channel protein’ for
2. (So) more ferroportin (in cell-surface
3 ferroportin
membranes);
(3 x AO3)
2. and 3. Accept
3. (So) more iron (ion) transport from – LOGY – – JUNE 2022
‘many’ for more
cytoplasm/cell;
06.3 Correct answer for 2 marks = 30.52:1 / 30.5:1 /
31:1;;
Accept for 1 mark,
31 (ratio not given)
OR
30:1 (incorrect rounding)
OR
200 (correct mass in healthy person)
(2 x AO2)
OR
1526 (correct iron concentration in person with
haemochromatosis)
OR Accept for 1 mark any
correct ratio (not
simplified) e.g. 763:25 11
6104 : 200 (correct ratio, but not simplified)
or 1526:50
How to answer it
Iron Ions, Haemochromatosis, and Plasma Calculations
What this question tests
This exam sequence evaluates your understanding of biological molecules and ions (specifically inorganic iron ions in haemoglobin), your ability to interpret unfamiliar biochemical pathway flowcharts, and your quantitative problem-solving skills involving concentrations, unit conversions, and ratios.
Function and Properties of Iron Ions
✅ Correct Answer
Any two of the following marking points:
- Ions are charged / polar (Accept Fe²⁺ or Fe³⁺).
- Ions are part of haem (haemoglobin).
- Ions bind, associate, or load with oxygen (forming oxyhaemoglobin) to transport oxygen.
💡 Key Knowledge
Inorganic ions have specific roles depending on their properties. Iron ions (Fe²⁺) sit at the centre of the haem group in haemoglobin proteins, temporarily binding oxygen molecules in the lungs and releasing them in respiring tissues.
🧠 Exam Technique
Read command words carefully. Explain requires you to link a property of the ion directly to how it allows the red blood cell to perform its specific physiological role.
❌ Common Errors
Students often state general properties of water or ions without linking them back to red blood cells and oxygen transport, or they incorrectly refer to iron atoms rather than ions (Fe²⁺).
Interpreting Biochemical Pathways (Haemochromatosis)
✅ Correct Answer
To gain all 3 marks using Figure 7:
- Point 1: There is less or no hydrolysis/breakdown of ferroportin (due to absence of hepcidin).
- Point 2: Therefore, more ferroportin remains in the cell-surface membranes.
- Point 3: As a result, more iron ions are transported from the cell cytoplasm into the blood plasma.
💡 Key Knowledge
Figure-based questions test your ability to track directional arrows and relational blocks. Follow the pathway step-by-step: hormone missing → protein not broken down → increased transport across membranes.
🧠 Exam Technique
Always anchor your explanation using the specific names provided in the prompt and diagram (e.g., ferroportin , hydrolysis , cytoplasm , plasma ). Do not rely on outside biological knowledge not shown in the flowchart.
❌ Common Errors
Vague references like "protein is destroyed" instead of using the flowchart's specific term hydrolysed ferroportin , or missing the causal link between membrane protein levels and iron transport rates.
Quantitative Calculations & Ratios
✅ Correct Answer
30.52 : 1 (or 30.5 : 1, or 31 : 1)
Award 2 marks for a correct final ratio. Award 1 mark for intermediate correct values if the final ratio is incorrect or unsimplified (e.g., 6104 : 200).
📐 Step-by-Step Calculation
- Mass in haemochromatosis patient: Given directly as 6104 µg .
- Calculate mass in healthy person: Concentration = 50 µg dm⁻³ , Volume = 4000 cm³ . Convert volume to dm³: 4000 cm³ = 4 dm³ .
- Mass = Concentration × Volume = 50 µg dm⁻³ × 4 dm³ = 200 µg .
- Calculate ratio: 6104 : 200 → divide both sides by 200 to simplify: 30.52 : 1 .
🧠 Exam Technique
Always show your intermediate working! If your final division or rounding goes wrong, working out individual masses (200 µg and 6104 µg) secures the fallback 1 mark.
❌ Error Traps to Avoid
- Forgetting to convert cm³ to dm³ (failing to divide 4000 by 1000).
- Failing to format as a ratio relative to 1 (e.g. writing just 30.52 without : 1 loses a mark if specified).
Topics
Biology · 3.1 Biological molecules
Question and mark scheme from the AQA AS Level Biology examination, Paper 1, June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.