How does the respiratory system supply oxygen for physical activity and sport?
The pathway of air, the structure of the alveoli, gaseous exchange, the mechanics of breathing, and the lung volumes that change during exercise.
A focused answer to AQA GCSE PE on the respiratory system: the pathway of air, the structure of the alveoli, gaseous exchange, the mechanics of breathing, and how lung volumes change with exercise.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
AQA wants you to trace the pathway of air into the lungs, describe how the alveoli are adapted for gaseous exchange, explain how oxygen and carbon dioxide are exchanged, describe the mechanics of breathing, and define the lung volumes that change during exercise.
The pathway of air
Air follows a fixed route into the lungs: mouth and nose then trachea (windpipe) then bronchi then bronchioles then alveoli. Learn this order, because questions often ask you to put the structures in sequence.
The alveoli and gaseous exchange
Oxygen diffuses from the alveoli (high oxygen) into the blood (low oxygen), where it binds to haemoglobin in red blood cells. Carbon dioxide diffuses the other way, from the blood into the alveoli, to be breathed out.
The mechanics of breathing
Breathing in (inspiration) and out (expiration) is caused by the diaphragm and the intercostal muscles (between the ribs).
- Breathing in: the diaphragm contracts and flattens, the intercostal muscles contract and lift the ribs up and out. The chest volume increases, pressure drops, and air rushes in.
- Breathing out: the diaphragm and intercostal muscles relax, the chest volume decreases, pressure rises, and air is pushed out.
Lung volumes
At rest, tidal volume is small (around half a litre). During exercise the body needs more oxygen and must remove more carbon dioxide, so tidal volume and breathing frequency rise, which uses up part of the air normally held in reserve. AQA expects four named volumes: tidal volume (air moved per normal breath), inspiratory reserve volume (the extra you can force in beyond a normal breath), expiratory reserve volume (the extra you can force out) and residual volume (the air that always remains so the lungs never fully empty). During exercise the rising tidal volume eats into both reserve volumes, while the residual volume stays the same.
Linking ventilation to oxygen delivery
The respiratory system never works alone. Air drawn into the alveoli supplies the oxygen that the cardiovascular system then carries (bound to haemoglobin) to the muscles, and it removes the carbon dioxide the muscles produce. A bigger tidal volume and faster breathing rate are useless without the increased cardiac output to transport the gases, which is why endurance training improves both systems together.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20192 marksDescribe two ways the structure of the alveoli is adapted for efficient gaseous exchange.Show worked answer →
A Paper 1 short-answer item, one mark per correctly described adaptation.
Award marks for any two of: a large surface area (millions of alveoli) gives more room for diffusion; walls one cell thick give a short diffusion distance; a moist lining helps gases dissolve; and a rich capillary network maintains a steep concentration gradient.
Markers want the feature plus its effect. "They are thin" is weaker than "thin walls give a short diffusion path", which secures the mark.
AQA 20214 marksExplain how the mechanics of breathing change during exercise to increase the oxygen supplied to the working muscles.Show worked answer →
An AO2 question linking the breathing mechanism to performance demand.
Award marks for: the diaphragm and intercostal muscles contract more forcefully, the rib cage lifts further and the chest cavity expands more, lowering the pressure so a larger volume of air is drawn in. Both tidal volume (air per breath) and breathing rate increase, so minute ventilation rises.
The top marks come from the link: more air reaches the alveoli per minute, so more oxygen diffuses into the blood for the muscles, supporting aerobic respiration during the activity.
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Sources & how we know this
- AQA GCSE Physical Education (8582) specification — AQA (2016)