A-LevelBiologyImmunity9700/22 · May/June 2024 · Q66 Marks

Some people who are infected with HIV have HIV/AIDS.

(a)State the full term for HIV.[1]
(b)Following transmission of HIV, early diagnosis of infection and treatment with anti-retroviral therapy (ART) helps to control the spread of the pathogen and prevent HIV/AIDS. Suggest why treating people who have developed HIV/AIDS with ART may help to reduce the number of overall deaths from infectious diseases, such as cholera, TB and malaria.[2]
(c)(i)Studies suggest that people who are infected with HIV may be at a higher risk of heart disease. One cause of heart disease is the narrowing of the lumen of one or both of the main coronary arteries. A coronary artery bypass graft (bypass graft) is a surgical operation that uses healthy blood vessels to divert blood around diseased sections of coronary arteries. The main choice of blood vessel to use for a bypass graft is known as the internal thoracic artery. [Figure 6.1] is a diagram of an external view of the heart to show a double bypass graft. The blood vessels used in the bypass graft shown in Fig. 6.1 are the great saphenous vein from the leg and the internal thoracic artery. Draw a cross (X) on Fig. 6.1 to show an area of the right coronary artery that has been bypassed.[1]
(c)(ii)After surgery, the wall of the great saphenous vein becomes thicker. Suggest and explain why it is important for the wall of the vein to become thicker after surgery.[2]

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 (May/June 2024). The mark or mark type is shown in brackets.

[1] human immunodeficiency virus ;
[1] helps to, increase / maintain / AW, number of, T-,lymphocytes / T-helper cells ; A helps to prevent death of T-lymphocytes / AW A T-cells
[1] maintains / improves / AW, strength of, immune system / immune response ;
[1] increases chance of recovery from, infectious / opportunistic, disease ; AW
[1] idea that decreases risk of having / helps prevent, other (opportunistic) diseases ;
[1] AVP; e.g. (can) decrease viral load / reduce number of HIV
[1] X is positioned above the join on the coronary artery on, left-hand side of Fig. 6.1 / right heart; R if placed at the junction of the vein and artery
[1] can withstand high(er) blood pressure / less likely to burst ; R collapse A idea that blood pressure is now higher
[1] (so) blood vessel may last longer ; A otherwise unlikely to last a long time
[1] (in tunica media) more (smooth) muscle / thicker (smooth) muscle layer / more elastic fibres ;
[1] detail; e.g. helps, onward movement / faster flow, of blood / AW A otherwise does not have enough, (smooth) muscle / elastic fibres, for onward movement / required speed of flow, of blood
[1] thicker tunica, externa / adventitia ; A more collagen

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