One molecule of haemoglobin can combine with
Correct answer: B. four molecules of oxygen
- A. one molecule of oxygen
- B. four molecules of oxygen
- C. two molecules of oxygen
- D. an unlimited number of oxygen molecules
Explanation
Haemoglobin has four polypeptide chains, each with an iron containing haem group that binds one oxygen molecule, giving a maximum of four. Binding is cooperative, so the attachment of the first oxygen makes the next ones easier, and this is what gives the oxygen dissociation curve its S shape. Full saturation is reached in the lung capillaries within a fraction of a second.
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About Gaseous Exchange in Lungs
Gaseous exchange in the lungs occurs across the thin, moist alveolar and capillary surfaces, where oxygen and carbon dioxide diffuse down partial pressure gradients. The topic covers alveolar adaptations, ventilation, the role of haemoglobin in oxygen transport, carbon dioxide carriage, and the difference between external gas exchange and cellular respiration.
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