CAIE A Level Biology 9700 · Transport in mammals
The table shows the percentage saturation of adult human haemoglobin at different partial pressures of oxygen (pO2) at 37°C and pH 7.4.
| pO2 (kPa) | Saturation (%) |
|---|---|
| 2 | 20 |
| 4 | 40 |
| 6 | 65 |
| 8 | 85 |
| 12 | 97.5 |
Using the data, describe the relationship between pO2 and percentage saturation of haemoglobin. Explain the importance of this relationship in the transport of oxygen and how it is affected by a decrease in pH (for example, in respiring tissues).
6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
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