AQA GCSE Combined Science: Trilogy Biology Paper 1 (Foundation), 2023: Question 5
10 marks · Standard Demand difficulty · Extended Answer
Identify components of the human respiratory system, describe adaptations for gas exchange, and explain the differences in gas composition between inhaled and exhaled air using provided data.
Practise this questionQuestion
Question text
05 Figure 8 shows the human breathing system.
Figure 8
05.1 Name parts A and B.
Choose answers from the box.
[2 marks]
alveolus bronchus capillary trachea
A
B
05.2 Where does gas exchange happen in the breathing system?
[1 mark]
Tick ( ) one box.
A B 26C D
05.3 Give two ways that the lungs are adapted for efficient gas exchange.
[2 marks]
Table 3 shows the percentage of gases in air breathed into the lungs and air breathed
out of the lungs.
Table 3
Percentage (%) in air Percentage (%) in air
Gas
breathed in breathed out
Oxygen 21 16
Carbon dioxide 0.04 4
Nitrogen 78 27 78
05.4 Explain the differences in the air breathed into the lungs and the air breathed out of
the lungs.
[4 marks]
05.5 The percentages given in each column of Table 3 do not add up to 100%.
Suggest one reason why.
[1 mark]
Mark scheme
Show the mark scheme
Question 5
AO /
Question Answers Extra information Mark
Spec. Ref.
05.1 (A) trachea 1 AO1
4.2.1
(B) bronchus 1 4.2.2.2
must be in this order
AO /
Spec. Ref.
05.2 D 1 AO1
4.2.2.2
AO /
Spec. Ref.
05.3 any two from: 2 AO1
• many alveoli 4.2.2.2
4.1.3.1
• large surface area
• short diffusion distance allow short distance for gas to
travel across
• wall of alveolus only one cell allow (wall of) alveolus is thin
thick do not accept cell wall
• wall of blood capillaries only allow thin (wall of) blood
one cell thick capillary
do not accept cell wall
• good blood supply
• well ventilated
ignore moist
AO /
Question Answers Mark
Spec. Ref.
05.4 Level 2: Relevant points (reasons / causes) are identified, given in 3–4 AO2
detail and logically linked to form a clear account. 4.2.2.2
4.4.2.1
1–2
Level 1: Points are identified and stated simply, but their relevance
is not clear and there is no attempt at logical linking.
No relevant content 0
Indicative content
• less oxygen in exhaled air (than inhaled air)
o (because) the body has used some oxygen
o for respiration
• more carbon dioxide in exhaled air (than inhaled air)
o (because) carbon dioxide is produced in respiration
o carbon dioxide can cause poisoning (in high concentration)
o (so) needs to be removed from the body
• no difference in the percentage of nitrogen in inhaled and
exhaled air
o (because) nitrogen is not used by the body
• more water vapour / moisture in air breathed out
o (because) water is produced in respiration
• exhaled air is warmer (than inhaled air)
o (because) energy is transferred during respiration
o thermal energy of body warms the exhaled air
For Level 2, explanation(s) and difference(s) must be given
AO /
Spec. Ref.
05.5 any one from: 1 AO3
• there are other gases present allow named gas eg argon 4.2.2.2
• water (vapour) is present 4.4.2.1
• the numbers are rounded
Total Question 5 10
How to answer it
The Human Breathing System & Gas Exchange
What this question tests
This question assesses your ability to identify the structures of the respiratory system, explain how the lungs are adapted for diffusion, and link the composition of exhaled air to the process of aerobic respiration.
Identifying Structures
Correct Answers
- A: Trachea
- B: Bronchus
Exam Technique
Always use the words provided in the box! Examiners often include "distractors" like capillary or alveolus to see if you can distinguish between large airways and microscopic structures.
Location of Gas Exchange
Correct Answer
Tick Box: D
Key Knowledge
Gas exchange occurs in the alveoli. In Figure 8, label D points to the tiny air sacs at the very end of the bronchioles. This is where oxygen diffuses into the blood and CO₂ diffuses out.
Adaptations for Efficiency
Correct Answers (Any two)
- Large surface area (many alveoli).
- Short diffusion distance (walls are only one cell thick).
- Good blood supply (maintains concentration gradient).
- Well ventilated (brings in fresh O₂).
Common Errors
- "Cell Walls": Never say the lungs have "cell walls". Only plants have cell walls. Say "the wall is one cell thick".
- "Moist": While the lungs are moist, the mark scheme specifically says to ignore this as an adaptation for efficiency in this context.
Explaining Air Composition
Comparing Inhaled vs Exhaled Air
How to get 4/4 Marks
This is a Level 2 question. To get full marks, you must not only state the difference but also explain why it happens using your knowledge of respiration.
1. Oxygen (21% → 16%)
Difference: Less oxygen is breathed out.
Reason: Oxygen is used by the body for aerobic respiration to release energy.
2. Carbon Dioxide (0.04% → 4%)
Difference: More CO₂ is breathed out.
Reason: CO₂ is produced as a waste product of respiration.
3. Nitrogen (78% → 78%)
Difference: No change.
Reason: Nitrogen is not used or produced by the body.
4. Water Vapour & Temp
Difference: Exhaled air is warmer and contains more water vapour.
Reason: Water is a product of respiration; body heat warms the air.
Data Analysis
Correct Answer (Any one)
- There are other gases present (e.g. Argon).
- Water vapour is present but not listed in the table.
- The numbers have been rounded.
Examiner Insight
Students often forget that air isn't just Oxygen, Nitrogen, and CO₂. Noble gases like Argon make up about 1% of the atmosphere, which accounts for the "missing" percentage in many exam tables.
Topics
Biology · B2: Organisation · B4: Bioenergetics · B1: Cell Biology
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Biology Paper 1 (Foundation), 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.