The role of red blood cells is to transport oxygen around the body. The oxygen-carrying capacity of red blood cells varies from species to species. The oxygen-carrying capacity depends partly on the size and structure of the red blood cells and their haemoglobin content. The graph shows the oxygen dissociation curve for haemoglobin and myoglobin. Myoglobin is present inside muscle cells and acts as an oxygen store. (i) The decrease in percentage saturation with oxygen of myoglobin from 6 kPa to 4 kPa is $$\(3 \%\)$$. Calculate the difference between this decrease and the decrease for haemoglobin from 6 kPa to 4 kPa . (2) Answer .......................................................... .. \% (ii) Describe the effect of the partial pressure of oxygen on the percentage saturation with oxygen of myoglobin. Use values from the graph to support your answer. (2) ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ (iii) Suggest why the dissociation curve for myoglobin is to the left of the curve for haemoglobin. fromer (2) ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................ ................................................................................................................................................................................................................................................................................
Exam No：wbi11-01-que-20240508. Year：2024 Question No：(c)
Answer:
- 26 (1)
- 23 (1)
A description that makes reference to the following points:
- as partial pressure (of oxygen) drops from 12 to \{1 / 2 / 3 / 4\} ( kPa ) the percentage saturation of oxygen \{remains at 80 to 100 \% / remains fairly constant / drops slightly\} (1)
- partial pressure (of oxygen) drops sharply at low levels of oxygen
OR
- percentage saturation (of oxygen) drops sharply below \{1 / 2 / 3 / 4\} (kPa) (1)
- percentage saturation (of oxygen) \{remains at 80 to 100 \% / remains fairly constant / drops slightly\} at high partial pressures (1)
An answer that makes reference to two of the following points:
- because myoglobin has a higher affinity for oxygen (than haemoglobin) (1)
- so that it will (only) release the oxygen when partial pressures are low (1)
- because haemoglobin cannot supply enough oxygen to respiring muscle cells / so that myoglobin can supply enough oxygen to respiring muscle cells (1)
- 23 (1)
A description that makes reference to the following points:
- as partial pressure (of oxygen) drops from 12 to \{1 / 2 / 3 / 4\} ( kPa ) the percentage saturation of oxygen \{remains at 80 to 100 \% / remains fairly constant / drops slightly\} (1)
- partial pressure (of oxygen) drops sharply at low levels of oxygen
OR
- percentage saturation (of oxygen) drops sharply below \{1 / 2 / 3 / 4\} (kPa) (1)
- percentage saturation (of oxygen) \{remains at 80 to 100 \% / remains fairly constant / drops slightly\} at high partial pressures (1)
An answer that makes reference to two of the following points:
- because myoglobin has a higher affinity for oxygen (than haemoglobin) (1)
- so that it will (only) release the oxygen when partial pressures are low (1)
- because haemoglobin cannot supply enough oxygen to respiring muscle cells / so that myoglobin can supply enough oxygen to respiring muscle cells (1)
Knowledge points:
CH1 - Molecules, Transport And Health
Solution:
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