A-LevelBiologyInfectious diseases9700/21 · Oct/Nov 2023 · Q413 Marks

Some people who are infected with HIV develop HIV/AIDS. (a) Fig. 4.1 shows the number of people that have been newly infected with HIV (new infections) in 2018 across the world and the percentage changes in the number of new infections since 2010. [Fig. 4.1]

(a)(i)State the full name of the pathogen HIV.[1]
(a)(ii)Using only the data in Fig. 4.1, state what can be concluded about the change in number of new HIV infections across the world between 2010 and 2018. You may use the letters in Fig. 4.1 to identify the regions of the world.[4]
(b)People who develop HIV/AIDS have fewer T-helper cells as the pathogen destroys these cells. This makes them more susceptible to tuberculosis (TB). Explain why people with HIV/AIDS are more likely to develop TB.[4]
(c)A person infected with HIV may develop a heart condition called cardiac tamponade. The pericardium is a thin sac surrounding the heart, as shown in the healthy heart in Fig. 4.2. When a person develops cardiac tamponade, the pericardium starts to fill with blood. This prevents the ventricles functioning efficiently. [Fig. 4.2] People with cardiac tamponade experience a variety of symptoms including low blood pressure and an increased breathing rate. Suggest why a person with cardiac tamponade would experience symptoms of low blood pressure and an increased breathing rate.[4]

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 2023). The mark or mark type is shown in brackets.

[1] human immunodeficiency virus ;
[4] any four from:
there is a decrease in the percentage infections in most regions / AW ;
ref. to exceptions to this decreasing trend; e.g. B (Eastern Europe and Central Asia ) / D (Middle East and North Africa)
allow no overall trend if mp 1 and mp 2 not awarded
the biggest percentage decrease, in E (East and Southern Africa);
the smallest percentage decrease, in G (Latin America);
data quote to support described trend;
AVP;
[4] any four from:
tuberculosis / TB, is an opportunistic, disease / infection ;
weakened immune system ;
(fewer T-helper cells so a ) less effective primary immune response ;
(fewer helper T-cells so) less cytokine secreted ;
less, phagocytosis of the pathogens / AW ; A ref. to angry macrophages
fewer B-lymphocytes, stimulated / AW, to divide by mitosis and form plasma cells;
fewer antibodies secreted so fewer pathogens destroyed ;
ref. to latent TB becoming activated;
AVP; e.g. 'weak' / no, response to (BCG) vaccine so, fewer / no, memory cells
TB is caused by, a bacterial pathogen / Mycobacterium tuberculosis I Mycobacterium bovis
[4] any four from:
1 ref. to compression on ventricles ;
2 (so) volume of the ventricles reduces / ventricles cannot fully increase in size / AW;
3 less blood, filling / leaving, ventricles (each cardiac cycle);
4 idea that ventricular, contraction / systole, less powerful / weaker / less forceful;
5 less blood pumped to the, pulmonary / systemic, circulation (per, contraction / cardiac cycle / unit time ; A lungs / rest of body
faster breathing rate to compensate for
6 consequence in, lungs / rest of body ; e.g. less oxygen, diffuses / AW, into the blood
less carbon dioxide, diffuses / AW, out of the blood
less oxygen delivered to the tissues / AW
7 faster breathing rate to (try and) increase quantity of oxygen, absorbed / AW (in the lungs);
A increase quantity of carbon dioxide excreted
8 AVP; e.g. heart / cardiac muscle, does not receive enough, glucose / oxygen