AQA GCSE Combined Science: Trilogy Biology Paper 1 (Higher), June 2025: Question 6

19 marks · Standard Demand difficulty · Extended Answer

Analyze microscopy of ciliated cells, calculate real cell size, explain anaemia's effect on muscle fatigue, calculate viable red blood cells produced from stem cells, and evaluate blood transfusion sources.

Practise this question

Question

Question 6 consists of six parts: an electron micrograph showing cilia lining an oviduct (Figure 7); questions 06.1 and 06.2 asking for evidence of electron microscopy and the function of oviduct ciliated cells; question 06.3 asking to calculate real mean length in micrometres from an image length of 6 mm at 1.5 x 10³ magnification; question 06.4 explaining why anaemia causes muscle fatigue; question 06.5 calculating usable red blood cells produced from 5 x 10⁵ stem cells (each yielding 100,000 cells, 35% suitable) in standard form; and question 06.6 evaluating red blood cells from stem cells versus whole blood donation using Table 2 containing cost and yield data.
Question text

06 Ciliated cells have small hair-like structures called cilia on the cell surface.

Ciliated cells are found in the trachea and in the oviducts.

Oviducts are part of the female reproductive system.

Figure 7 shows cilia lining an oviduct.

Figure 7

06.1 Give one piece of evidence that an electron microscope was used to produce the

image shown in Figure 7.

Do not refer to colour in your answer.

[1 mark]

06.2 Describe the function of ciliated cells in the oviduct.

[1 mark]

06.3 The mean length of the cilia in an image was 6 mm.

The cilia were viewed at a magnification of 1.5 × 103

*20Calculate the real mean length of the cilia.*

Give your answer in micrometres (μm).

[5 marks]

Real mean length = μm

Red blood cells are a type of cell found in humans.

People with anaemia do not have enough red blood cells.

06.4 Explain why a person with anaemia is likely to experience muscle fatigue.

[2 marks]

Scientists have produced red blood cells from stem cells in a laboratory.

The scientists:

• collected a sample of blood from a donor

• extracted 5 × 105 stem cells from the sample.

Each stem cell was developed into 100 000 red blood cells.

*2135% of the red blood cells made from stem cells are suitable to use in a patient.*

06.5 Calculate the number of red blood cells made from the donor’s sample that could be

used in a patient.

Give your answer in standard form.

[4 marks]

Number of red blood cells (in standard form)24 =

06.6 Patients with anaemia are sometimes given a blood transfusion.

A blood transfusion is when a patient is given blood.

*22The patient can be given red blood cells:*

• produced from stem cells in a laboratory

or

• from a whole blood donation.

Table 2 gives information about the two sources of red blood cells.

Table 2

Red blood cells Red blood cells

produced from stem cells from a whole blood donation

• A small sample of blood is • 470 cm3 of blood is collected

collected from the patient. from a donor.

• The total cost is £15 per 10 cm3 • The blood donation is separated

of cells produced. into its different parts.

• All of the new cells can function • Red blood cells make up 45% of

for 120 days. whole blood.

• The total cost of a blood

donation is £130.

• The cells can function for

between 1 and 120 days.

Evaluate the use of red blood cells:

• produced from stem cells in a laboratory

• from a whole blood donation.

You should refer to costs in your answer.

[6 marks]

Extra Space

Mark scheme

Show the mark scheme Mark scheme for Question 6 detailing answers: 06.1 accepts high resolution, high magnification, or 3D image (1 mark); 06.2 accepts moving an egg/embryo/ovum (1 mark); 06.3 details magnification equation recall, rearrangement, substitution (6 / 1.5 x 10³), calculation (0.004 mm), and conversion to 4 µm (5 marks); 06.4 awards 1 mark for less oxygen transported and 1 mark for anaerobic respiration producing lactic acid; 06.5 shows steps yielding 1.75 x 10¹⁰ in standard form (4 marks); 06.6 provides a 3-level descriptor marking grid and indicative content evaluating pros, cons, and relative costs (6 marks).

Question 6

AO /

Question Answers Extra information Mark

Spec. Ref.

06.1 any one from: 1 AO3

4.1.1.5

• high resolution allow a high level of detail

• high magnification

• 3D image

• cilia can be seen in detail ignore subcellular structures can

be seen

AO /

Spec. Ref.

06.2 move / transport egg / embryo / ignore move / transport dust / 1 AO2

ovum / mucus bacteria / pathogens / sperm 4.1.1.3

4.3.1.6

AO /

Spec. Ref.

06.3 recall of equation AO1

size of image ignore use of equation triangle 1

magnification =

size of real object

rearrangement of equation AO2

size of image 1

size of real object =

magnification

substitution

6 allow 6 1 AO2

1.5 × 103 1500

allow substitution of incorrectly

converted value

0.004 (mm) allow answer using incorrectly 1 AO2

converted value

conversion

4 (μm) allow conversion to μm at any 1 AO2

stage

4.1.1.5

AO /

Spec. Ref.

06.4 less oxygen (is transported) to allow less oxyhaemoglobin 1 AO2

cells / tissues / organs / muscles transported 4.2.2.3

4.4.2.1

4.4.2.2

(so) anaerobic respiration ignore less aerobic respiration 1

produces lactic acid ignore reference to energy

AO /

Spec. Ref.

total amount of red blood cells 10

5 allow 5 × 10

06.5 (5 × 10 × 100 000 =) 1 AO2

50 000 000 000 4.2.2.3

percentage calculation allow 5 × 1010 1

50 000 000 000 × 35

× 35 100

allow 5 × 1010 × 0.35

allow a correctly calculated

percentage calculation from an

incorrectly calculated number of

red blood cells

17 500 000 000 1

standard form

1.75 × 1010 allow correct standard form from 1

an incorrectly calculated number

of red blood cells

alternative route

× 100 000 = 35 000 (1)

35 000 × 500 000 (1)

17 500 000 000 (1)

1.75 × 1010 (1)

AO /

Question Answers Mark

Spec. Ref.

06.6 Level 3: A judgement, strongly linked and logically supported by a 5–6 AO2

sufficient range of correct reasons, is given.

20 Level 2: Some logically linked reasons are given. There may also 3–4 AO3

be a simple judgement.

Level 1: Relevant points are made. They are not logically linked. 1–2 AO3

No relevant content 0 4.1.2.3

4.2.2.3

Indicative content

Advantages of blood from stem cells:

• reduces the need for volunteer blood donors

• only a small sample of blood is required (to produce the

necessary blood cells)

• can produce a large(r) quantity of red blood cells

• (blood cells are all new) so last longer in the patient

• no rejection or no need to tissue match

• no ethical objection to receiving blood (because it is from the

patient)

• we can produce blood that is a rare / specific blood group / type

• less / no risk of infection (from contaminated blood)

• whole blood donation takes more time / processing to separate

the blood into its parts

Disadvantages of blood from stem cells:

o a blood donation is still required

o not tried and tested or it is a (relatively) new technology

o white blood cells, plasma and platelets are not collected

o cannot use for other purposes as only red blood cells collected

Costs:

red blood cells from donation are cheaper than blood from stem

cells

red blood cells from whole donation costs 61 / 62 pence per

cm3

or

red blood cells from whole donation costs £6.15 per 10 cm3

red blood cells from stem cells cost £1.50 per cm3

lab grown blood is 2 / 3 times more expensive than whole blood

donation

(470 cm3 of red blood cells) from stem cells cost £705

(211.5 cm3 of red blood cells) from stem cells cost £317.25

211.5 cm3 of red blood cells from whole donation costs £130

For Level 3, advantages and disadvantages for a treatment

are needed and a reference to costs.

For Level 2, advantages / disadvantages for a treatment

are needed and a reference to costs.

For Level 1, relevant points are made.

Total Question 6 19

How to answer it

Ciliated Cells, Microscopy & Stem Cell Blood Transfusions

📋 What This Question Tests
  • Cell Biology & Microscopy: Differentiating electron micrographs (SEM 3D images) from light micrographs and calculating real cell size ( Real = Image / Magnification ) with unit conversions (mm to µm).
  • Human Transport & Respiration: Specialised cell functions (ciliated cells in reproduction), consequences of anaemia, and how lack of oxygen forces anaerobic respiration leading to muscle fatigue.
  • Stem Cells & Evaluation: Multi-step quantitative problem solving in standard form, and evaluating medical applications (stem-cell-derived red blood cells vs donor blood transfusions) incorporating cost analysis.

Part 06.1: Electron Microscopy Evidence

Identifying micrographs | 1 Mark

✅ Acceptable Answers (Any One)

  • High resolution / high level of detail
  • High magnification
  • It shows a 3D image (three-dimensional surface view)
  • Cilia can be seen in detail

❌ Common Errors & Traps

  • Mentioning colour: The question explicitly says: "Do not refer to colour in your answer." Writing "it is black and white" scores 0 marks.
  • Vague statements: Saying "subcellular structures can be seen" is ignored because internal organelles are not visible here.
Mark scheme note: AO3 (1 mark). Scanning electron microscopes (SEM) provide incredible depth of field, creating a distinctive 3D surface contour.

Part 06.2: Function of Ciliated Cells in the Oviduct

Specialised cell adaptations | 1 Mark

✅ Correct Answer

To move / transport the egg / ovum / embryo (or mucus) along the oviduct towards the uterus.

❌ Wrong Organ System Traps

  • Mixing up lungs and oviducts: Do NOT say "to sweep dust, mucus, or pathogens away". That is the function of ciliated cells in the trachea/airways!
  • Do NOT write "to move sperm" (sperm have their own flagella to swim).
Mark scheme note: AO2 (1 mark). Always read the organ location carefully in physiology questions!

Part 06.3: Magnification Calculation

Five-step calculation with unit conversion | 5 Marks

📐 Step-by-Step Calculation

Given data: Image length ( I ) = 6 mm; Magnification ( M ) = 1.5 × 10³ = 1500; Find Real length ( A ) in µm.

  1. Step 1 (Recall): State formula: Magnification = Image size / Actual real size [1 mark]
  2. Step 2 (Rearrange): Real size = Image size / Magnification [1 mark]
  3. Step 3 (Substitute): Real size = 6 / (1.5 × 10³) = 6 / 1500 [1 mark]
  4. Step 4 (Calculate in mm): 0.004 mm [1 mark]
  5. Step 5 (Convert to µm): Multiply by 1000 ( 0.004 × 1000 ) = 4 µm [1 mark]

🧠 Exam Technique: Convert First Strategy

You can also convert mm to µm at the very beginning to avoid working with tiny decimals:

  • 6 mm × 1000 = 6000 µm
  • Real size = 6000 / 1500 = 4 µm

Both routes award full 5 marks!

❌ Common Errors

  • Dividing by 1000 instead of multiplying when converting mm to µm.
  • Incorrectly expanding standard form: 1.5 × 10³ = 1500 (not 15 000).

Part 06.4: Anaemia and Muscle Fatigue

Circulation, Respiration & Lactic Acid | 2 Marks

✅ Mark Scheme Breakdown

  • Mark 1 (Cause): Less oxygen is transported to muscle cells / tissues (due to fewer red blood cells / less haemoglobin).
  • Mark 2 (Consequence): Muscles must respire anaerobically, which produces lactic acid (causing muscle fatigue).

❌ Examiner Pitfall: "Less Energy"

  • Students often write: "So less energy is produced which makes them tired."
  • The mark scheme specifically states: "ignore less aerobic respiration / ignore reference to energy."
  • To earn the second mark, you must name anaerobic respiration and lactic acid!

Part 06.5: Stem Cell Production Calculation

Multi-step math & Standard Form | 4 Marks

📐 Step-by-Step Working

  1. Step 1: Calculate total red blood cells produced
    5 × 10⁵ stem cells × 100 000 RBCs per stem cell
    = 500 000 × 100 000 = 50 000 000 000 (or 5 × 10¹⁰ ) [1 mark]
  2. Step 2: Apply the percentage (35%)
    (50 000 000 000 / 100) × 35 or 5 × 10¹⁰ × 0.35 [1 mark]
  3. Step 3: Calculate the usable amount
    = 17 500 000 000 [1 mark]
  4. Step 4: Convert to standard form
    = 1.75 × 10¹⁰ [1 mark]

🧠 Error-Carried-Forward (ECF)

Even if you make an arithmetic error in Step 1 or 2, you can still gain marks for correctly applying 35% and converting your final incorrect number into correct standard form (e.g. A × 10ᵇ where 1 ≤ A < 10).

❌ Trap: Forgetting Standard Form

Leaving the final answer as 17 500 000 000 loses the 4th mark. Always double-check if the question specifies: "Give your answer in standard form."

Part 06.6: Extended Evaluation (6-Mark Question)

Evaluating Stem Cells vs Donor Blood Transfusions | 6 Marks

Criteria for Level 3 (5–6 marks): Advantages AND Disadvantages AND Costs analysed with a supported Judgement.

💡 Advantages of Stem Cell RBCs

  • No rejection / no tissue matching needed: Cells originate from the patient.
  • Safety: No risk of transmitting blood-borne infections from donors.
  • Supply: Reduces reliance on volunteer donors; can produce rare blood types on demand.
  • Longer lifespan: All new cells last 120 days (donor cells only last 1–120 days, average ~60 days).

⚠️ Disadvantages of Stem Cell RBCs

  • Incomplete: Only produces red blood cells; cannot supply platelets, plasma, or white blood cells.
  • Unproven: Relatively new, less tested technology compared to routine transfusions.
  • Still requires an initial blood sample from the patient.

💰 Crucial Cost Comparison (Required for 5–6 Marks)

You must process the table data to compare costs directly:

  • Whole blood volume of RBCs: 45% of 470 cm³ = 211.5 cm³ of red blood cells.
  • Cost of donor RBCs: £130 for 211.5 cm³ = £0.61 (or 61p) per cm³ (or £6.15 per 10 cm³).
  • Cost of stem cell RBCs: £15 per 10 cm³ = £1.50 per cm³.
  • Comparative deduction: Stem cell red blood cells are much more expensive (more than double the cost: ~2.4 times more expensive).

🧠 Model Conclusion / Judgement

"In conclusion, while stem cell-derived red blood cells are significantly more expensive (£15 per 10 cm³ compared to ~£6.15 per 10 cm³ for donor blood) and only provide red blood cells, they are superior for patients with rare blood types or severe immune sensitivities because they eliminate the risk of rejection and infection and all survive for the full 120 days."

Topics

Biology · B1: Cell Biology · B2: Organisation · B4: Bioenergetics

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Biology Paper 1 (Higher), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.