10.1. Infectious diseases
A subsection of Biology, 9700, through 10. Infectious diseases
Listing 10 of 208 questions
In March 2019, a tropical cyclone in the south-west Indian Ocean caused widespread flooding in a number of countries. The flooding and the damage caused by the cyclone meant that many people were at serious risk of cholera. After the natural disaster occurred, many different areas reported outbreaks of cholera. Within a short time the disease had spread widely and large numbers of people were affected. Cholera is caused by a bacterial pathogen. Name the bacterial pathogen that causes cholera. Suggest and explain why the people affected by the cyclone were at serious risk of cholera. In addition to the standard treatment for cholera, antibiotics are recommended for people who are moderately ill or seriously ill with the disease. Doxycycline is one of the main antibiotics used for the treatment of cholera. Doxycycline enters the pathogen and binds to one of the subunits of the bacterial ribosome. This prevents growth and reproduction of the bacterial cell. Suggest and explain how binding of doxycycline to ribosomes stops growth of the bacterial cell. Penicillin, which used to be prescribed for the treatment of cholera, has a different mechanism of action to doxycycline. State which part of the bacterial cell is affected by the action of penicillin. Mozambique was one of the countries badly affected by the cyclone. As part of the effort to prevent a greater number of cases of cholera from occurring, two different approaches were taken. • Approximately 900 000 doses of the oral cholera vaccine were sent to Mozambique and a large-scale vaccination programme was organised. • Medical centres were set up in Mozambique to treat people with cholera. Suggest and explain how the two different approaches helped to prevent a greater number of cases of cholera from occurring.
9700_m21_qp_22
THEORY
2021
Paper 2, Variant 2
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Tuberculosis (TB) is a major cause of ill health worldwide. State the name of a bacterium that causes TB in humans. is a scanning electron micrograph of bacteria that cause TB. X Y X Y magnification ×21 000 Calculate the actual length of the bacterial cell shown in , along the line X–Y. Write the formula you will use in the box. Give your answer in micrometres (μm) to two significant figures. formula actual length = μm Bacteria are unicellular prokaryotic cells with a diameter of 1–5 μm. State two other structural features that would identify a cell as prokaryotic. The World Health Organization (WHO) Global Tuberculosis Report for 2019 published data on the estimated number of deaths from TB and HIV / AIDS in 2018. All deaths of people from TB who were infected with HIV were also counted as deaths of people with HIV / AIDS. shows these data. The dark grey boxes show the estimated number of deaths of people from TB who were also counted as deaths of people with HIV / AIDS. 0.00 0.25 0.50 0.75 millions of deaths in 2018 1.00 1.25 1.50 deaths of people from TB deaths of people with HIV / AIDS not infected with HIV with HIV / AIDS from TB A student used the data in to predict that measures to control the spread of HIV will decrease the number of deaths from TB. Discuss whether the data in support this prediction. In healthy people, the number of T-helper cells ranges from 500 to 1200 cells per cm3 of blood. In untreated people infected with HIV, the number of T-helper cells can decrease to below 200 cells per cm3 of blood. Explain how a low number of T-helper cells makes it more likely that untreated people infected with HIV will die if they are also infected with TB.
9700_m22_qp_22
THEORY
2022
Paper 2, Variant 2
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Approximately 2 × 109 people in the world are currently infected with the bacterial disease tuberculosis (TB) caused by Mycobacterium tuberculosis. Early diagnosis is important so that treatment can begin. APOPO is a non-profit organisation that has trained African giant pouched rats, Cricetomys gambianus, to use their sense of smell to detect M. tuberculosis. They do this by sniffing a sample of thick mucus from the lungs of people who may have TB. The African giant pouched rats are able to detect the presence of M. tuberculosis with an accuracy of 87–93%. shows an African giant pouched rat. The type of receptor cell used by African giant pouched rats to detect M. tuberculosis is the same as that used in human taste buds. Name this type of receptor cell. Suggest why African giant pouched rats trained to detect M. tuberculosis may also be able to detect other species of Mycobacterium that cause TB. The African giant pouched rat belongs to the kingdom Animalia in the domain Eukarya. Complete Table 8.1 to show the full classification of the African giant pouched rat. Table 8.1 kingdom Animalia Chordata class Mammalia Rodentia family Nesomyidae species gambianus Differences between members of the domain Eukarya and members of the domain Bacteria include the presence or absence of particular membrane-bound cell structures. Outline other differences in the characteristic features of members of the domain Eukarya and members of the domain Bacteria. Describe, with reference to the structure of viruses, how viruses are classified.
9700_m24_qp_42
THEORY
2024
Paper 4, Variant 2
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Questions Discovered
208