AQA A-Level Biology Paper 1, June 2025: Question 10

15 marks · Medium difficulty · Extended Answer

Describe translation roles of ribosomes, tRNA, and ATP; leaf adaptations for gas exchange; and the pathway of blood from a kidney to the coronary arteries.

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Question

Question 10 is divided into three parts: 10.1 asks to describe the roles of ribosomes, tRNA and ATP in the process of translation for 6 marks; 10.2 asks to describe and explain the adaptations of leaves that maximise gas exchange, without referring to organelles, for 4 marks; 10.3 asks to describe the pathway taken by blood between a kidney and the coronary arteries, including names of major blood vessels and heart valves involved, for 5 marks.
Question text

10.1 Describe the roles of ribosomes, tRNA and ATP in the process of translation.

[6 marks]

10.2 Describe and explain the adaptations of leaves that maximise gas exchange.

Do not refer to organelles in your answer.

[4 marks]

10.3 Describe the pathway taken by blood between a kidney and the coronary arteries.

Include names of the major blood vessels (arteries and veins) and heart valves

involved.

[5 marks]

Mark scheme

Show the mark scheme Mark scheme for Question 10. 10.1 awards up to 6 marks for points detailing ribosome binding to mRNA, reading codons, tRNA carrying specific amino acids, complementary anticodon-codon pairing, ATP usage in amino acid attachment and peptide bond formation, and translocation. 10.2 awards up to 4 marks for adaptations such as numerous stomata, mesophyll air spaces, large surface area of cell membranes, large surface area to volume ratio, and thin leaves for a short diffusion pathway. 10.3 awards up to 5 marks for tracing blood from the renal vein to the vena cava and right atrium, through the atrioventricular valve to the right ventricle, via the semi-lunar valve to the pulmonary artery, pulmonary vein, left atrium, atrioventricular valve, left ventricle, semi-lunar valve, aorta, and coronary artery.

Question Marking Guidance Mark Comments

1. Ribosome attaches to mRNA; 1. Accept rough

endoplasmic reticulum

for ribosome

1. Accept

associates/binds/joins

for ‘attaches’

1. Ignore rER

2. Accept has/

2. Ribosome covers 2 (mRNA) codons/base

presents/attaches/

triplets

exposes for ‘covers’

OR

2. Accept ‘first codon’

for ‘start’ codon

Ribosome moves/attaches to start codon/AUG; 6 max

10.1 (6 x

3. ATP (energy) used when amino acid attaches to AO1)

tRNA;

4. Accept

corresponding/’amino

4. tRNA brings specific amino acid (to ribosome);

acid coded for by

codon’ for ‘specific’

5. (tRNA) anticodons bind to complementary

(mRNA) codons;

6. ATP (energy) used to form peptide bond(s);

7. Ribosome moves along mRNA forming

polypeptide

OR

– A-LEVEL BIOLOGY – 7402/1 –

Ribosome moves along mRNA to stop codon;

1. Many stomata; Ignore moist

membranes

2. Stomata allow (gas) diffusion;

3. Air spaces in mesophyll;

4 max

10.2 4. Large surface area of cells/cell membranes for (4 x

(rapid) diffusion; AO1)

5. Large (leaf) surface area to volume ratio so

high/increases diffusion (rate);

6. Thin (leaves) so short diffusion distance/

pathway;

18 Question Marking Guidance Mark Comments

2. Accept tricuspid

1. Renal vein (to) vena cava (to) right atrium;

valve

2. (Via) atrio-ventricular valve (to) right ventricle;

2 and 4 Penalise

using ‘AV valve’ for

3. (Via) semi-lunar valve (to) pulmonary artery (to)

atrio-ventricular valve

pulmonary vein;

only once

4. Left atrium (via) atrio-ventricular valve (to) left

10.3 (5 x 3. Accept pulmonary

ventricle;

AO1) valve for ‘semi-lunar

valve

5. (Via) semi-lunar valve (to) aorta to coronary

artery;

4. Accept

bicuspid/mitral valve

5. Accept aortic valve

for ‘semi-lunar valve

How to answer it

AQA A-Level Biology Revision Guide

Protein Synthesis, Plant Gas Exchange & Cardiovascular Transport

Assessment Overview

What This Question Tests

This 15-mark synoptic section evaluates your foundational recall and precision (AO1) across three core modules: molecular biology, plant exchange surfaces, and mammalian mass transport.

  • Part 10.1 (6 marks): Detailed sequential knowledge of translation, specifically distinguishing the independent roles of ribosomes, transfer RNA (tRNA), and ATP.
  • Part 10.2 (4 marks): Leaf anatomy adaptations obeying Fick's Law (surface area, concentration gradient, diffusion path) while strictly respecting negative constraints (no cell organelles allowed).
  • Part 10.3 (5 marks): Tracing systemic and pulmonary circulation from a named organ (kidney) to cardiac supply (coronary arteries), naming all required blood vessels and internal heart valves in proper sequence.
Question 10.1 • 6 Marks

Roles of Ribosomes, tRNA, and ATP in Translation

Describe the roles of ribosomes, tRNA and ATP in the process of translation.

✅ Mark Scheme Breakdown (Any 6 of 7)

  1. Ribosome attaches to mRNA (associates / binds).
  2. Ribosome covers 2 codons (base triplets) at a time OR moves to / attaches at the start codon ( AUG ).
  3. ATP provides energy for amino acid attachment to tRNA.
  4. tRNA transports a specific amino acid to the ribosome.
  5. tRNA anticodon binds to complementary mRNA codon via base pairing.
  6. ATP provides energy to form peptide bonds between adjacent amino acids.
  7. Ribosome moves along mRNA forming polypeptide OR moves until it reaches a stop codon.

🧠 Exam Technique & Structure

  • Use three clear headings: Group your points explicitly under Ribosome, tRNA, and ATP. This ensures you do not omit any of the three required components.
  • Specify ATP's two distinct roles: Many students write "ATP provides energy for translation" and get zero. State explicitly: (1) attaching amino acid to tRNA, and (2) peptide bond synthesis.
  • Pairing terminology: Always state complementary base pairing between the anticodon on tRNA and the codon on mRNA.

💡 Key Knowledge Recap

  • Ribosome: Has two subunits made of rRNA and proteins; provides binding grooves that hold two tRNA molecules adjacent to each other.
  • tRNA: Cloverleaf structure held by hydrogen bonds; contains an anticodon loop at one end and an amino acid binding site at the 3' CCA terminal.
  • Peptide Bond Formation: Catalysed by peptidyl transferase (an enzymatic rRNA component of the ribosome) powered by ATP hydrolysis.

❌ Common Errors & Pitfalls

  • Confusing transcription with translation: Describing RNA polymerase, unwinding DNA, or splicing pre-mRNA.
  • Vagueness with tRNA: Stating tRNA "makes" amino acids or carries "genetic information" rather than carrying a specific amino acid.
  • Missing the two-codon rule: Forgetting that a ribosome fits exactly two codons / tRNA molecules simultaneously during elongation.
Examiner Insight: Full 6 marks are easily attained by candidates who avoid generic descriptions of protein synthesis and systematically address what the ribosome does (binds mRNA, moves along, accommodates 2 codons), what tRNA does (anticodon-codon binding, brings specific amino acid), and what ATP does (energy for charging tRNA, energy for peptide bonds).
Question 10.2 • 4 Marks

Leaf Adaptations for Gas Exchange

Describe and explain the adaptations of leaves that maximise gas exchange. Do not refer to organelles in your answer.

✅ Mark Scheme Breakdown (Any 4 of 6)

  • Feature 1: Many stomata;
  • Explanation 1: Stomata allow rapid (gas) diffusion / short diffusion pathway into internal tissues.
  • Feature 2: Intercellular air spaces in the mesophyll (spongy mesophyll layer);
  • Explanation 2: Provides a large surface area of cell walls/membranes for rapid diffusion.
  • Feature 3: Large (leaf) surface-area-to-volume ratio; so increases rate of diffusion.
  • Feature 4: Thin leaves / thin tissue layers; so provides a short diffusion distance / pathway.

❌ Fatal Error: Mentioning Organelles

The rubric explicitly states: "Do not refer to organelles in your answer."

  • Disallowed words: Chloroplasts, mitochondria, vacuoles, nuclei.
  • Any mention of "chloroplasts positioned near the surface" or "chloroplasts absorbing light" earns 0 marks for that point and wastes valuable exam time.
  • Note also: The mark scheme says "Ignore moist membranes". Stick strictly to physical dimensions and tissue-level structures.

🧠 Exam Technique: "Describe & Explain"

Always format as paired statements:

  • Describe: Name the physical structural adaptation (e.g., thin blade / flat shape).
  • Explain: State the exact biophysical mechanism linked to Fick's Law (e.g., leads to a short diffusion distance).
  • Describe: Intercellular air spaces in spongy mesophyll → Explain: creates large internal surface area for rapid gas diffusion.

💡 Linking to Fick's Law

Rate of Diffusion ∝ (Surface Area × Concentration Gradient) ÷ Diffusion Pathway

  • Large Surface Area: Flat blade, many stomata, loosely packed spongy mesophyll.
  • Short Diffusion Distance: Thin lamina, leaf cells never more than a few cell layers from stomata or air spaces.
Examiner Insight: High-scoring candidates paired every descriptive feature with a direct functional explanation. Candidates losing marks typically either forgot to explain why a feature helped (omitting "short diffusion distance" or "large surface area") or broke the negative constraint by writing about chloroplasts.
Question 10.3 • 5 Marks

Cardiovascular Route: Kidney to Coronary Arteries

Describe the pathway taken by blood between a kidney and the coronary arteries. Include names of the major blood vessels (arteries and veins) and heart valves involved.

🗺️ Sequential Pathway Overview

Kidney → Renal vein → Vena cava → Right atrium → Atrioventricular / Tricuspid valve → Right ventricle → Semi-lunar / Pulmonary valve → Pulmonary artery → Lungs → Pulmonary vein → Left atrium → Atrioventricular / Bicuspid valve → Left ventricle → Semi-lunar / Aortic valve → Aorta → Coronary arteries

✅ Mark Scheme Breakdown (5 Marks Total)

  1. Mark 1: Renal vein → vena cava → right atrium;
  2. Mark 2: (Via) atrio-ventricular valve (tricuspid) → right ventricle;
  3. Mark 3: (Via) semi-lunar valve (pulmonary valve) → pulmonary artery → (lungs) → pulmonary vein;
  4. Mark 4: Left atrium → (via) atrio-ventricular valve (bicuspid / mitral) → left ventricle;
  5. Mark 5: (Via) semi-lunar valve (aortic valve) → aorta → coronary artery.

❌ Marking Pitfalls & Penalties

  • Abbreviation Penalty: Do not just write AV valve ! The mark scheme states: "Penalise using 'AV valve' for atrio-ventricular valve only once." Write atrio-ventricular valve in full at least once, or use specific anatomical names (tricuspid / bicuspid).
  • Starting/Ending point mistakes: Starting at "renal artery" instead of "renal vein" loses Mark 1 immediately. The blood is leaving the kidney!
  • Missing the pulmonary circuit: Forgetting that deoxygenated blood from the vena cava must go to the lungs via the pulmonary artery and return via the pulmonary vein before reaching the aorta.
Examiner Insight: Every mark point requires correct biological ordering. Candidates frequently lose marks by omitting the valves entirely despite the question explicitly commanding: "Include names of the major blood vessels... and heart valves involved." Always underline the key prompts in the stem.

Topics

Biology · 3.1 Biological molecules · 3.3 Organisms exchange substances with their environment · 3.4 Genetic information, variation and relationships between organisms

Question and mark scheme from the AQA A-Level Biology examination, Paper 1, June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.