O-LevelBiologyRespiration5090/22 · May/June 2016 · Q58 Marks

Table 5.1 shows a number of processes that occur in the lungs and thorax (chest cavity). [Table 5.1 showing processes: diffusion into red blood cells, diffusion into the alveoli, the diaphragm contracts, the diaphragm relaxes, the external intercostal muscles contract, the internal intercostal muscles relax, the ribs rise, the ribs fall, pressure in the thorax increases, pressure in the thorax decreases]

(a)Carbon dioxide arrives at the lungs in capillaries. Place a tick (✓) in each box against a process involved in removing carbon dioxide from the blood and expelling it to the atmosphere.[4]
(b)Table 5.2 shows the percentage of oxygen in inspired and expired air of three people, J, K and L. [Table 5.2 showing person (J, K, L), % of oxygen in inspired air (20.5 for J, K, L), % of oxygen in expired air (15.0 for J, 16.5 for K, 18.5 for L)] Describe the differences shown in Table 5.2 and suggest reasons for them.[4]

Mark scheme

Marking points from the official mark scheme (May/June 2016). The mark or mark type is shown in brackets.

[4] ✓ diffusion into the alveoli (box 2) ;
✓ the diaphragm relaxes (box 4) ;
✓ the ribs fall (box 8) ;
✓ pressure in the thorax increases (box 9);
[4] 1. any stated difference between inspired and expired % O2;
2. O2 used in respiration;
3. Person J – the most/more (than normal) O2 absorbed/used ;
4. Person J - active/taking exercise/athlete/pregnant/high respiratory rate/high blood cell or red blood cell count AW ;
5. Person K - moderate activity/normal ;
6. Person L – low O2 absorption/use ;
7. Person L – (named) lung disease/anaemia/ smoker/inactive/sleeping/elderly /dying/low respiratory rate/reference to low red blood cell count/carboxyhaemoglobin ; A any disease that would restrict O2 uptake

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