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A-Level Biology OCR A

Oxygen Alveoli Haemoglobin Gradient Erythrocytes Air Low Steep

Oxygen from alveoli diffuses into capillaries, then erythrocytes, binding to haemoglobin. The concentration gradient is maintained because initially, oxygen levels are low in erythrocytes, and as oxygen binds, the free oxygen concentration in the erythrocyte remains low, facilitating further uptake.

Oxygen from alveoli diffuses into capillaries, then erythrocytes, binding to haemoglobin. The concentration gradient is maintained because initially, oxygen levels are low in erythrocytes, and as oxygen binds, the free oxygen concentration in the erythrocyte remains low, facilitating further uptake.

Front Describe the route oxygen takes from the air in the alveoli to haemoglobin and explain how the concentration gradient is maintained.
Back Carrying oxygen:
  • Oxygen diffuses from alveoli into capillaries and then into erythrocytes, binding to haemoglobin
  • Initially, oxygen levels in the erythrocytes are low - steep conc gradient between inside of erythrocytes and air in alveoli
  • As soon as 1 oxygen binds to a haem group, molecule changes shape and it makes it easier for more oxytgen mols to bind
  • Bc oxygen is bound to haemoglobin, free oxygen conc in erythrocyte remains low - steep diff gradient maintained until all haemoglobin is saturated

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