Fig. 1 shows blood from a small sample after it has been spun in a centrifuge. A nurse then counted red blood cells in samples from two groups. Table 1 show...
Question 1 Report
Fig. 1 shows blood from a small sample after it has been spun in a centrifuge. A nurse then counted red blood cells in samples from two groups. Table 1 shows the mean counts.
| Group | Mean number of red blood cells / million per mm3 |
|---|---|
| Adults living at sea level | 4.8 |
| Adults living at 3500 m altitude | 5.6 |
(a) Name the fluid at the top of the tube in Fig. 1. [1]
(b) Describe the main function of red blood cells. [1]
(c) State the difference between the mean red blood cell counts of the two groups. [1]
(d) Explain why a person living at high altitude may benefit from having more red blood cells. [2]
(e) Name the substance in red blood cells that combines with oxygen. [1]
(f) Describe one adaptation of a red blood cell for carrying oxygen. [2]
Answer Details
(a) The fluid at the top of the centrifuged tube is plasma. [1]
(b) The main function of red blood cells is to transport oxygen. [1]
(c)
\[5.6-4.8=0.8\text{ million per mm}^3\]
The difference is 0.8 million red blood cells per mm3. [1]
(d) At high altitude there is less available oxygen, or lower oxygen pressure, in the air. More red blood cells increase the amount of oxygen that can be transported to body cells. [2]
(e) The oxygen-carrying substance is haemoglobin. [1]
(f) A red blood cell has a biconcave shape, giving it a large surface area for oxygen exchange. It has no nucleus, leaving more space for haemoglobin. [2]
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