Describe the process of gaseous exchange at the alveolar-capillary interface. (4 marks)
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Sample Answer
- Gaseous exchange occurs through diffusion, where gases move from areas of high concentration to areas of low concentration.
- At the alveoli, oxygen diffuses from the air sacs (where concentration is high) into the surrounding capillaries (where concentration is low).
- Simultaneously, carbon dioxide diffuses from the capillaries (high concentration) into the alveoli (low concentration) to be exhaled.
- This exchange is facilitated by the extremely thin walls of both alveoli and their surrounding capillaries.
- The large surface area created by millions of alveoli enhances the diffusion rate.
- Once in the bloodstream, oxygen binds to haemoglobin in red blood cells for transport.
- Carbon dioxide is carried in the blood primarily as bicarbonate ions before being exhaled.
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Sample Answer
- Gaseous exchange occurs through diffusion, where gases move from areas of high concentration to areas of low concentration.
- At the alveoli, oxygen diffuses from the air sacs (where concentration is high) into the surrounding capillaries (where concentration is low).
- Simultaneously, carbon dioxide diffuses from the capillaries (high concentration) into the alveoli (low concentration) to be exhaled.
- This exchange is facilitated by the extremely thin walls of both alveoli and their surrounding capillaries.
- The large surface area created by millions of alveoli enhances the diffusion rate.
- Once in the bloodstream, oxygen binds to haemoglobin in red blood cells for transport.
- Carbon dioxide is carried in the blood primarily as bicarbonate ions before being exhaled.