AQA AS Level Biology Paper 1, June 2024: Question 1

6 marks · Medium difficulty · Short Answer

Name structures in the human gas exchange system, match physiological processes and pathways to letters on an alveolus and blood vessel diagram, and describe and explain an adaptation of a single alveolus for gas exchange.

Practise this question

Question

Three-part biology exam question on the human gas exchange system. Question 01.1 shows a diagram of the respiratory system (Figure 1) with lines pointing to the trachea (A) and intercostal muscles (B), asking to name them for 2 marks. Question 01.2 presents a diagram of an alveolus with associated blood vessels and labeled arrows C, D, E, F, and G (Figure 2), and a table (Table 1) asking students to match letters to statements about diffusion of oxygen, transport of gas mixture, and blood pressure, worth 2 marks. Question 01.3 asks to describe and explain one adaptation of a single alveolus for gas exchange for 2 marks.
Question text

01.1 Figure 1 shows a diagram of the human gas exchange system.

Figure 1

Structure B is muscle. The volume of the thorax is increased when structure B

contracts.

Name the structures labelled A and B.

[2 marks]

A

B 3

01.2 Figure 2 is a diagram of an alveolus and a blood vessel associated with the alveolus.

The direction of the movement of substances is shown by the arrows labelled C, D, E,

F and G.

Figure 2

Complete Table 1 by writing the correct letter, C, D, E, F or G, in the box next to each

statement. You may use each letter once, more than once or not at all.

[2 marks]

Table 1

Statement

represents the diffusion of oxygen

represents the transport of a gas mixture

represents blood moving at the highest pressure4

01.3 Describe and explain one adaptation of a single alveolus for gas exchange.

[2 marks]

Mark scheme

Show the mark scheme Mark scheme showing correct answers for the three parts. Question 01.1 awards 2 marks for naming A as trachea and B as external intercostal muscle. Question 01.2 awards 2 marks based on the number of correct letters in Table 1: F for diffusion of oxygen, D for transport of gas mixture, and C for blood moving at highest pressure. Question 01.3 awards 2 marks for stating the epithelium is a single cell layer or thin/flat, and explaining this provides a short diffusion pathway.

Question Marking Guidance Mark Comments

1. (A) Trachea; 2 1. Accept cartilage

01.1 (2 x

2. (B) External intercostal (muscle); AO1)

3 correct = 2 marks;;

2 correct = 1 mark;

1 correct = 0 marks

Statement

F represents the diffusion of oxygen 2

01.2 (2 x

AO1)

represents the transport of a gas

D

mixture

represents blood moving at the highest

C

pressure

1. (Epithelium is) single cell layer Ignore reference to

surface area

OR

2 1. Accept one cell

(Epithelium contains) thin/flat cells

01.3 (2 x thick

OR AO1)

1. Accept “has

Epithelium is thin; squamous epithelium”

2. (So) short diffusion pathway/distance;

How to answer it

Anatomy and Physiology of Human Gas Exchange

What this question tests

This question assesses core knowledge of the human gas exchange system (AO1), including gross anatomical structures, pulmonary ventilation mechanisms, vascular pathways, gas transport characteristics, and the ultrastructural adaptations of alveoli that facilitate efficient diffusion.

Question 01.1

Anatomy of the Gas Exchange System

Name the structures labelled A and B. [2 marks]

✅ Correct Answers

  • A: Trachea (Accept: cartilage)
  • B: External intercostal (muscle)

💡 Key Knowledge

Structure A is the main windpipe reinforced with C-shaped rings of cartilage to keep the airway open during pressure changes. Structure B refers to the muscles situated between the ribs responsible for pulling the ribcage up and out during inspiration.

🧠 Exam Technique

Be precise with anatomical terminology. For structure B, simply writing "intercostal muscle" is insufficient for top-level credit; you must specify external intercostal muscle because internal intercostals serve the opposite (expiratory) function.

❌ Common Errors

Students frequently confuse internal and external intercostal muscles, or incorrectly label structure A as the oesophagus or bronchus.

Mark breakdown: 2 marks total (1 mark per correct identification). AO1 = 2 marks.
Question 01.2

Gaseous Movement and Circulation

Complete Table 1 by writing the correct letter (C, D, E, F, or G) for each statement. [2 marks]

✅ Correct Answers

  • Represents the diffusion of oxygen: F
  • Represents the transport of a gas mixture: D
  • Represents blood moving at the highest pressure: C

💡 Key Knowledge

F shows oxygen moving from the alveolar air space into the capillary blood. D represents air entering and leaving the alveolus (a mixture of N₂, O₂, CO₂, and water vapour). C represents the pulmonary artery/arteriole bringing deoxygenated blood directly from the right ventricle, which pumps blood under high pressure.

🧠 Exam Technique

Carefully trace the direction of arrows in diagrams. Examiners award tiered marks: 3 correct = 2 marks, 2 correct = 1 mark, 1 or 0 correct = 0 marks.

❌ Common Errors

Confusing incoming pulmonary arteriole blood pressure (high pressure from heart pumping) with capillary or venous pressure.

Mark breakdown: 2 marks for all 3 correct; 1 mark for 2 correct. AO1 = 2 marks.
Question 01.3

Alveolar Adaptations for Gas Exchange

Describe and explain one adaptation of a single alveolus for gas exchange. [2 marks]

✅ Correct Answers

  • Point 1: (Epithelium is) single cell layer / thin / flat cells / squamous epithelium.
  • Point 2: (So) short diffusion pathway / distance.

💡 Key Knowledge

Fick's Law dictates that rate of diffusion is inversely proportional to the diffusion distance. A single layer of squamous epithelial cells minimises this distance, increasing the rate of gas exchange.

🧠 Exam Technique

This is a describe and explain question. You must pair a structural feature (description) with its functional consequence (explanation). Examiner tip: Do not mention large surface area here; the question specifically asks for an adaptation of a single alveolus, not the whole lung tissue.

❌ Common Errors

Losing the second mark by failing to link the thin wall/single layer to a short diffusion pathway, or incorrectly discussing overall lung surface area instead of focusing on the single alveolar wall structure.

Mark breakdown: 1 mark for the structural description, 1 mark for the explanation linking it to diffusion distance. AO1 = 2 marks.

Topics

Biology · 3.3 Organisms exchange substances with their environment

Question and mark scheme from the AQA AS Level Biology examination, Paper 1, June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.