Gas Exchange (Edexcel GCSE Combined Science: Biology): Flashcards
Exam code: 1SC0
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Alveoli
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Alveoli
Tiny rounded air sacs in the lungs that form the gas exchange surface, adapted to maximise the diffusion of gases.
Why are the lungs described as the gas exchange surface in humans?
They are adapted to maximise the exchange of gases (oxygen and carbon dioxide) by diffusion.
How does having many alveoli aid gas exchange?
It provides a large surface area for the exchange of gases.
How are the walls of the alveoli adapted to speed up gas exchange?
They are made of a single layer of flattened cells, which minimises the diffusion distance.
How is a steep concentration gradient maintained across the alveoli?
Ventilation keeps oxygen high and carbon dioxide low in the alveolar air, and a good blood supply brings blood high in carbon dioxide and low in oxygen.
Why is there a layer of moisture on the surface of the alveoli?
Gases dissolve in the moisture, which helps them to diffuse.
List the key adaptations of the alveoli for efficient gas exchange.
Many alveoli giving a large surface area.
A single layer of flattened cells for a short diffusion distance.
Ventilation and a good blood supply to maintain a steep concentration gradient.
A moist surface so gases dissolve.
The alveoli are surrounded by a layer of flattened cells to minimise the diffusion distance.
single
A layer of on the alveoli surface helps diffusion as the gases .
moisture / dissolve
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