CIE iGCSE Co-Ordinated Science B10. Diseases and immunity Exam Style Questions Paper 3
Question
(a) Human immunodeficiency virus (HIV) is a sexually transmitted infection. The number of new HIV infections in one country was monitored.
The results are shown in Fig. 4.1.
The number of new infections has decreased since 2002.
(i) Calculate the difference in number of new HIV infections between 2002 and 2009.
▶️Answer/Explanation
Solution:
From Fig. 4.1, the number of new HIV infections in 2002 is approximately 7000, and in 2009, it is approximately 3100. The difference is calculated as:
7000 – 3100 = 3900
So, the difference in the number of new HIV infections between 2002 and 2009 is 3900.
3900
(ii) Suggest two reasons why the number of new HIV infections has decreased since 2002.
▶️Answer/Explanation
Solution:
Two possible reasons for the decrease in the number of new HIV infections since 2002 could be:
- Increased awareness and education about HIV prevention methods, such as the use of condoms.
- Improved access to antiretroviral therapy (ART) and better healthcare services, which reduce the transmission of the virus.
Any two from: use of condoms / femidoms; screening blood transfusions; education; use of clean needles / needle exchange programmes; regular HIV testing; preventative medication; AVP; e.g. practise of abstinence.
(iii) Place a tick (✓) in the box to show one way HIV can be transmitted.
| Option | Tick |
|---|---|
| holding hands | |
| sharing cooking utensils | |
| through breast milk | |
| genetically inherited |
▶️Answer/Explanation
through breast milk
(b) HIV infects white blood cells. Fig. 4.2 shows a photomicrograph of some blood. A white blood cell can be seen in the centre.
(i) Name the part of the white blood cell labelled X in Fig. 4.2.
▶️Answer/Explanation
Solution:
The part of the white blood cell labelled X is the nucleus.
nucleus
(ii) Name the other type of cells visible in Fig. 4.2.
▶️Answer/Explanation
Solution:
The other type of cells visible in Fig. 4.2 are red blood cells.
red blood cells
(iii) State two functions of white blood cells.
▶️Answer/Explanation
Solution:
Two functions of white blood cells are:
- Phagocytosis: Engulfing and digesting pathogens.
- Antibody production: Producing antibodies to neutralize pathogens.
phagocytosis; antibody production
(iv) Name the part of the blood that transports hormones.
▶️Answer/Explanation
Solution:
The part of the blood that transports hormones is the plasma.
plasma