How does the respiratory system supply oxygen for exercise?
The structure of the respiratory system, gas exchange at the alveoli, the composition of inhaled and exhaled air, and tidal volume and vital capacity.
A focused answer to Edexcel GCSE PE on the respiratory system: the main structures, gas exchange at the alveoli, the composition of inhaled and exhaled air, and the meaning of tidal volume and vital capacity and how they change with exercise.
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What this dot point is asking
Edexcel wants you to locate the main parts of the respiratory system, explain gas exchange at the alveoli, state the composition of inhaled and exhaled air, and define tidal volume and vital capacity, all applied to exercise.
The structure of the respiratory system
Gas exchange at the alveoli
The alveoli are highly adapted: a large surface area (there are millions of them) lets a lot of gas diffuse at once; thin walls (one cell thick) give a short diffusion distance; a rich capillary network keeps a steep concentration gradient by carrying gases away; and moist walls let gases dissolve. During exercise the muscles demand more oxygen and produce more carbon dioxide, so the gradient steepens and gas exchange speeds up to meet the demand of varying intensities (aerobic and anaerobic).
Composition of inhaled and exhaled air
Tidal volume and vital capacity
During exercise, tidal volume increases (each breath is deeper) and breathing rate increases, so more air, and therefore more oxygen, reaches the alveoli each minute. This change is necessary because the muscles need a faster supply of oxygen for aerobic energy release and a faster removal of carbon dioxide. The cardiovascular and respiratory systems work together: oxygen is taken into the lungs, transferred to the blood at the alveoli, transported by the blood to the muscles, and carbon dioxide is returned and breathed out.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20183 marksDescribe three features of the alveoli that make them well suited to gas exchange during exercise.Show worked answer →
A Component 1 short-answer question. One mark per correct feature.
Award marks for any three of: a very large surface area (millions of alveoli) so a lot of gas can diffuse at once; very thin walls (one cell thick) so the diffusion distance is short; a rich capillary network (good blood supply) to maintain a steep concentration gradient; and moist walls so gases dissolve before diffusing.
Markers want the feature linked to why it helps exchange, not just a list of words.
Edexcel 20224 marksTable 2 gives the composition of inhaled and exhaled air. Using the table, explain why the figures differ and how this difference increases during exercise.Show worked answer →
A Component 1 table (use of data) question, marks for reading the figures and explaining them.
Award marks for: inhaled air is about 21 percent oxygen and 0.04 percent carbon dioxide, while exhaled air is about 16 percent oxygen and 4 percent carbon dioxide; the drop in oxygen and rise in carbon dioxide happen because the body absorbs oxygen and releases carbon dioxide at the alveoli. During exercise the working muscles use more oxygen and produce more carbon dioxide, so the difference grows and breathing rate and depth rise to keep up.
The strongest answers quote the table values and link the change to muscle demand.
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Sources & how we know this
- Pearson Edexcel GCSE (9-1) Physical Education (1PE0) specification — Pearson Edexcel (2016)