10.1. Infectious diseases
A subsection of Biology, 9700, through 10. Infectious diseases
Listing 10 of 208 questions
The control of malaria is one of the top priorities of the World Health Organization (WHO). At present, there is no effective vaccine for the disease, so other preventative measures must be taken to control the spread of malaria. Describe one method of controlling the spread of malaria by targeting its vector and explain its effect. Explain why it has been difficult to develop an effective vaccine for malaria. Another method of preventing malaria is to take drugs, such as chloroquine, but resistance to these drugs among certain species of the malarial parasite is increasing. New drugs are being developed. A laboratory investigation was carried out to determine the effect of a new drug on two strains of the malarial parasite Plasmodium falciparum. The results are shown in . chloroquine-sensitive P. falciparum chloroquine-resistant P. falciparum percentage of parasites killed after 24h concentration of new drug / µmol dm–3 With reference to , compare the effect of increasing the concentration of the drug on the chloroquine-resistant and chloroquine-sensitive strains of P. falciparum. When a person becomes infected with the Human Immunodeficiency Virus (Hthey become more susceptible to infection by the malarial parasite. shows maps of Africa produced by the WHO. • a shows the percentage population of each country testing positive for HIV • b shows the percentage increase in malaria as a result of HIV infection in each country. 20.0% – 28.0% 10.0% – Suggest how HIV infection may have led to an increase in malarial infections in these countries.
9700_s10_qp_23
THEORY
2010
Paper 2, Variant 3
View
Almost 40% of adults with cystic fibrosis (CF) develop a form of diabetes known as cystic fibrosis-related diabetes (CFRD). This is thought to happen because the build-up of thick secretions in the pancreas destroys β cells. Explain how the destruction of β cells causes diabetes. The bacterium Pseudomonas aeruginosa can cause chronic (long-lasting) lung infections. A person with CFRD is likely to have poorer lung function and a greater likelihood of having a chronic lung infection than a person who has CF but does not have CFRD. An investigation was carried out to find out if the severity of damage to lung function in a person with CFRD is affected by • their gender • whether or not they have a chronic P. aeruginosa infection. The investigators measured lung function by recording the maximum volume of air that can be expelled from the lungs in the first one second of a forced expiration. This is known as FEV1. The lower the median FEV1, the poorer the lung function. Table 4.1 summarises the results of this investigation. All the 812 people in the study had cystic fibrosis. Table 4.1 without chronic P. aeruginosa infection with chronic P. aeruginosa infection male female male female with CFRD without CFRD with CFRD without CFRD with CFRD without CFRD with CRFD without CFRD number of people FEV1 71.1 71.4 53.6 73.6 49.0 59.0 42.0 61.0 With reference to Table 4.1 discuss whether or not there appears to be a positive correlation between having a chronic P. aeruginosa infection and having CFRD calculate the percentage difference between the FEV1 of males and females without CFRD and without P. aeruginosa infection. Show your working answer % outline the conclusions that can be drawn concerning the relationship between gender and the severity of lung damage in a person with CFRD and with P. aeruginosa infection. In a person with CF, damage to lung function and the increased likelihood of chronic infections are the result of the secretion of thick mucus. Explain why thick mucus is secreted in the lungs of a person with CF.
9700_s11_qp_41
THEORY
2011
Paper 4, Variant 1
View
State the name of the organism that causes cholera. NQR is an important respiratory enzyme located in the cell surface membrane of the bacterium that causes cholera. A student suggested that an inhibitor of the enzyme NQR could be used as a drug in the prevention and control of cholera. Suggest and explain how this inhibitor would function. Table 5.1 shows the statistics for cholera reported to the World Health Organization (WHO) in four regions of the world in 2008. Table 5.1 region number of cases number of deaths fatality rate / % Africa 179 323 5 074 2.83 Asia 10 778 0.64 Europe 0.00 North America 0.00 Total 190 130 5 143 Calculate the total cholera fatality rate for 2008. Show your working. answer % Apart from differences in total population size in each of the regions, suggest explanations for the differences shown in Table 5.1.
9700_s12_qp_22
THEORY
2012
Paper 2, Variant 2
View
Cholera is a disease caused by the bacterium Vibrio cholerae. The disease symptoms are caused by a toxin, produced by the bacterium, interacting with proteins in the cell surface membranes of epithelial cells in the human intestine. The cholera toxin is a protein and is composed of two subunits, A and B. Subunit A is made from one polypeptide and subunit B is made from five identical polypeptides. shows the structure of the cholera toxin. subunit A subunit B S Name: the level of structure that is only shown by a protein that has more than one polypeptide chain the part labelled S. The cholera toxin interacts with ion channels in the epithelial membranes, resulting in watery diarrhoea. These channels open, allowing ions to move from the epithelial cells into the lumen of the intestine. Name the process by which the ions move in this case. Due to the movement of ions into the lumen, water moves from the epithelial cells into the lumen. Name the process by which water moves and explain why it moves into the lumen. name explanation Large outbreaks of cholera are often associated with natural disasters. For example, following an earthquake in Pakistan in 2005, an estimated 20 000 cholera cases were reported in the vicinity, compared to approximately 1000 cases in the rest of the country. Describe the mode of transmission of cholera. Explain how natural disasters can sometimes result in transmission to more individuals.
9700_s12_qp_23
THEORY
2012
Paper 2, Variant 3
View
Questions Discovered
208