O-LevelBiologyTransport in Humans5090/22 · Oct/Nov 2015 · Q311 Marks

Fig. 3.1 shows blood pressure changes as blood flows through part of the circulatory system, beginning at the right atrium, travelling to the lungs, and ending in the pulmonary vein. [Figure 3.1]

(a)State which chamber of the heart is represented by C. Explain your answer. chamber C explanation[2]
(b)Explain the reasons for the regular changes in blood pressure in region D.[2]
(c)(i)Identify region E.[1]
(c)(ii)Describe and explain the chemical changes that occur.[3]
(d)Describe and explain how the shape of a graph drawn to show blood pressure changes as blood flows from the heart to the rest of the body and back again would differ from Fig. 3.1.[3]

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 2015). The mark or mark type is shown in brackets.

[2] right ventricle ; blood flows from right atrium to right ventricle/pressure increases ;
[2] increases when heart/ventricle + contracts/pumps; decreases when heart/ventricle + relaxes/doesn't pump;
[1] capillaries/lung/alveoli/air sac/venule;
[max 3] CO2 lost * ; O2 gained/oxygenated * ; haemoglobin/oxyhaemoglobin ; change in pH/less acidic; ref. to diffusion gradient/concentration gradient ;
[max 3] wider variations in pressure AW ; pressure high(er) AW ; left ventricle wall large/thick/more muscular ; blood has further to travel/takes longer; more or many fluctuations/undulations AW ;

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