O-LevelBiologyRespiration5090/21 · Oct/Nov 2014 · Q47 Marks
Fig. 4.1 shows the effect of exercise on the concentration of oxygen in the blood and the concentration of lactic acid in the muscles of a healthy person over a 5-minute period. [Figure 4.1]
- (a)Use Fig. 4.1 to find the time at which the person started to exercise.[1]
- (b)Name the process that causes the change in oxygen concentration during the first 2 minutes on Fig. 4.1.[1]
- (c)Suggest and explain how each of the two curves on Fig. 4.1 might be different if the person suffered from emphysema.[5]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2014). The mark or mark type is shown in brackets.
- [1] 0.3-0.4 minutes ;
- [1] aerobic respiration ;
- [max. 5] O2 curve not as high at start/finish;
- [max. 5] O2 curve drops more quickly / ORA ;
- [max. 5] damage to alveoli ;
- [max. 5] less surface area for O2 absorption ;
- [max. 5] less O2 to blood/muscles ;
- [max. 5] lactic acid curve rises sooner/higher / takes longer to return to normal;
- [max. 5] shorter period of aerobic / longer period anaerobic respiration ;
- [max. 5] more lactic acid build-up ;
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