CAIE A Level Biology 9700 · Transport in mammals
The table below shows the percentage saturation of haemoglobin with oxygen at different partial pressures of oxygen (pO₂) under two conditions: low CO₂ (5 kPa) and high CO₂ (8 kPa).
| pO₂ (kPa) | % saturation (low CO₂) | % saturation (high CO₂) |
|---|---|---|
| 2 | 20 | 12 |
| 4 | 50 | 35 |
| 6 | 75 | 60 |
| 8 | 88 | 78 |
| 10 | 95 | 88 |
| 12 | 98 | 94 |
Describe the role of red blood cells and haemoglobin in transporting oxygen and carbon dioxide. In your answer, explain the importance of the Bohr shift as shown by the data.
5 marks, so the mark scheme is looking for about 5 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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